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The Ras homologous (Rho) protein family of GTPases (RhoA, RhoB and RhoC) are the members of the Ras superfamily and regulate cellular processes such as cell migration, proliferation, polarization, adhesion, gene transcription and cytoskeletal structure. Rho GTPases function as molecular switches that cycle between GTP-bound (active state) and GDP-bound (inactive state) forms. Leukaemia-associated RhoGEF (LARG) is a guanine nucleotide exchange factor (GEF) that activates RhoA subfamily GTPases by promoting the exchange of GDP for GTP. LARG is selective for RhoA subfamily GTPases and is an essential regulator of cell migration and invasion. Here, we describe the mechanisms by which LARG is regulated to facilitate the understanding of how LARG mediates functions like cell motility and to provide insight for better therapeutic targeting of these functions.

Calcium Ca2+ regulation is a key component of numerous cellular functions. In cardiomyocytes, Ca2+ regulates excitation-contraction coupling and influences signaling cascades involved in cell metabolism and cell survival. Prolonged dysregulation of mitochondrial Ca2+ leads to dysfunctional cardiomyocytes, apoptosis and ultimately heart failure. VEGF promotes cardiomyocyte contractility by increasing calcium transients to control the strength of the heartbeat. Here, we describe a method to measure mitochondrial Ca2+ fluxes in human ventricular cardiomocytes after inducing stretch-mediated hypertrophy in vitro.

Peptidyl-tRNA hydrolase 2 (PTRH2; Bit-1; Bit1) is an underappreciated regulator of adhesion signals and Bcl2 expression. Its key roles in muscle differentiation and integrin-mediated signaling are central to the pathology of a recently identified patient syndrome caused by a cluster of Ptrh2 gene mutations. These loss-of-function mutations were identified in patients presenting with severe deleterious phenotypes of the skeletal muscle, endocrine, and nervous systems resulting in a syndrome called Infantile-onset Multisystem Nervous, Endocrine, and Pancreatic Disease (IMNEPD). In contrast, in cancer PTRH2 is a potential oncogene that promotes malignancy and metastasis. PTRH2 modulates PI3K/AKT and ERK signaling in addition to Bcl2 expression and thereby regulates key cellular processes in response to adhesion including cell survival, growth, and differentiation. In this Review, we discuss the state of the science on this important cell survival, anoikis and differentiation regulator, and opportunities for further investigation and translation. We begin with a brief overview of the structure, regulation, and subcellular localization of PTRH2. We discuss the cluster of gene mutations thus far identified which cause developmental delays and multisystem disease. We then discuss the role of PTRH2 and adhesion in breast, lung, and esophageal cancers focusing on signaling pathways involved in cell survival, cell growth, and cell differentiation.

Endosomal trafficking of cell surface receptors is essential to their function. Integrins are transmembrane receptors that integrate adhesion to the extracellular matrix with engagement of the cytoskeleton. Ligated integrins mediate diverse signals that regulate matrix assembly, cell survival, cell morphology, and cell motility. Endosomal trafficking of integrins modulates these signals and contributes to cell motility and is required for cancer cell invasion. The phosphoprotein PEA-15 modulates integrin activation and ERK MAP Kinase signaling. To elucidate novel PEA-15 functions we utilized an unbiased proteomics approach. We identified several binding partners for PEA-15 in the endosome including clathrin and AP-2 as well as integrin β1 and other focal adhesion complex proteins. We confirmed these interactions using proximity ligation analysis, immunofluorescence imaging, pull-down and co-immunoprecipitation. We further found that PEA-15 is enriched in endosomes and was required for efficient endosomal internalization of α5β1 integrin and cellular migration. Importantly, PEA-15 promotion of migration was dependent on PEA-15 phosphorylation at serines 104 and 116. These data support a novel endosomal role for PEA-15 in control of endosomal trafficking of integrins through an association with the β1 integrin and clathrin complexes, and thereby regulation of cell motility.

Sepsis is a severe dysregulated immune response to infection. Sepsis deaths represent 9% of cancer deaths in the U.S. Evidence of the effect of specific cancer sites on sepsis mortality risk remains limited, and no research has evaluated the effect of cancer treatment on the risk of sepsis death. We examined whether cancer sites and treatments differentially affect the risk of sepsis death compared to other-cause mortality, among the 94,784 Hawaii participants in the Multiethnic Cohort, including 29,255 cancer cases, using competing risk Cox proportional hazards regression. Cancer diagnosis at any site was associated with similar increases in sepsis and non-sepsis mortality risk (HR: 3.39 and 3.51, resp.). Colorectal cancer differentially affected the risk of sepsis and non-sepsis mortality with a 40% higher effect on the risk of sepsis death compared with non-sepsis mortality (RRR: 1.40, 95% CI: 1.14–1.72). Lung cancer was associated with a significantly lower increase in sepsis compared to non-sepsis mortality (HR: 1.22 and 3.0, resp., RRR: 0.39). Radiation therapy had no effect on sepsis mortality but was associated with higher risk of non-sepsis mortality (HR: 0.90 and 1.16, resp., RRR: 0.76), whereas chemotherapy was associated with higher risk of both sepsis and non-sepsis mortality (HR: 1.31 and 1.21, resp.). We conclude that the risk of sepsis-related mortality is differentially affected by cancer sites and treatments. These associations were consistent across sexes and ethnic groups.

Interest has emerged in the therapeutic potential of inhibiting store operated calcium (Ca2+) entry (SOCE) for melanoma and other cancers because malignant cells exhibit a strong dependence on Ca2+ flux for disease progression. We investigated the effects of deleting Selenoprotein K (SELENOK) in melanoma since previous work in immune cells showed SELENOK was required for efficient Ca2+ flux through the endoplasmic reticulum Ca2+ channel protein, inositol 1,4,5-trisphosphate receptor (IP3R), which is due to the role SELENOK plays in palmitoylating and stabilizing the expression of IP3R. CRISPR/Cas9 was used to generate SELENOK-deficiency in human melanoma cells and this led to reduced Ca2+ flux and impaired IP3R function, which inhibited cell proliferation, invasion, and migration. Ca2+-dependent signaling through calcineurin was inhibited with SELENOK-deficiency, and gene array analyses together with evaluation of transcript and protein levels showed altered transcriptional programs that ultimately disrupted stemness and pro-growth properties. In vivo investigations were conducted using the Grm1-Tg transgenic mouse strain that develops spontaneous metastatic melanoma, which was crossed with SELENOK-/- mice to generate the following littermates: Grm1-Tg/SELENOK-/-, Grm1-Tg/SELENOK-/+, Grm1-Tg/SELENOK+/+. SELENOK-deficiency in Grm1-Tg/SELENOK-/- male and female mice inhibited primary tumor growth on tails and ears and reduced metastasis to draining lymph nodes down to levels equivalent to non-tumor control mice. Cancer stem cell pools were also decreased in Grm1-Tg/SELENOK-/- mice compared to littermates. These results suggest that melanoma requires SELENOK expression for IP3R dependent maintenance of stemness, tumor growth and metastasic potential, thus revealing a new potential therapeutic target for treating melanoma and possibly other cancers.

Sepsis is a severe systemic inflammatory immune response to infection, which may lead to multiple organ failure and is associated with a 70% death rate. The risk of sepsis is higher in immunosuppressed individuals such as cancer patients. The risk of sepsis-related death among cancer patients may differ by cancer site and the administered cancer treatment. We examined the differences in the risk of sepsis-related mortality by cancer site and cancer treatment type among the 103,898 Hawaii participants of the Multiethnic Cohort Study (MEC), including 29,255 prevalent and incident cancer cases, followed for the period of 17-22 years. The participants were men and women aged 45-75 at cohort entry, primarily of Japanese American, Native Hawaiian or White race/ethnicity. Incident cancer cases were identified through linkage with the Hawaii Tumor Registry. Deaths due to sepsis (n=1,818) were identified as those with a primary or contributing cause of death ICD-10= A40-A41. Relative risk ratios (RR) and 95% confidence intervals (CI) were estimated using competing risk Cox regression with age as the time metric and with adjustment for participants' sex, race/ethnicity, and comorbidities at baseline (diabetes, cardiovascular disease, hypertension and stroke). Stratified analyses were conducted by sex and racial/ethnic group. The risk of sepsis-related death was not significantly different between cohort participants with and without cancer diagnosis (RR: 0.95; 95% CI: 0.85-1.06). In cancer-specific analyses, colorectal cancer diagnosis was associated with higher risk of sepsis death (RR: 1.41; 95% CI: 1.12-1.80), while lung cancer diagnosis was associated with lower risk of sepsis death (RR: 0.41; 95% CI: 0.31-0.55) compared to patients with cancer at all other organ sites. These associations were consistent across sexes and racial/ethnic groups, but only the association with lung cancer was statistically significant within most sex/ethnic groups. No association was observed between chemotherapy and sepsis death. Radiation treatment was associated with lower risk of sepsis death (RR: 0.69; 95% CI: 0.57-0.83). This association was consistent across sexes and racial/ethnic groups but was only statistically significant among Japanese and White women, possibly reflecting larger size and number of cancer cases with radiation therapy in these groups. In this study, we found that the risk of sepsis-related mortality is differentially affected by cancer at certain sites and by the type of cancer treatment administered. Future research should focus on biological and molecular mechanisms underlying these associations, with the hope of reducing the incidence of sepsis and sepsis-associated mortality. Citation Format: Yurii B. Shvetsov, Mari Ogino, Chloe Asato, Lynne R. Wilkens, Loic LeMarchand, Michelle Matter. Association of cancer site and treatment type with the risk of sepsis-related mortality in a multiethnic Hawaii population [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5794.

Significance Cell motility is a dynamic process that requires the directed application of force and continuous coordinated changes in cell adhesion and cytoskeletal architecture often in response to extracellular stimuli. Here we have defined a mechanism by which RSK2 can promote cell migration and invasion in response to promotility stimuli. We show that in response to these signals RSK2 directly binds the RhoGEF LARG and phosphorylates it, thereby promoting LARG activation of RhoA GTPases. Moreover, we find that RSK2 is important for epidermal growth factor activation of Rho GTPases. These results advance our understanding of cell motility, RSK kinase function, and LARG/RhoA activation by revealing that these pathways are integrated and the precise mechanism by which that is accomplished., Directed migration is essential for cell motility in many processes, including development and cancer cell invasion. RSKs (p90 ribosomal S6 kinases) have emerged as central regulators of cell migration; however, the mechanisms mediating RSK-dependent motility remain incompletely understood. We have identified a unique signaling mechanism by which RSK2 promotes cell motility through leukemia-associated RhoGEF (LARG)-dependent Rho GTPase activation. RSK2 directly interacts with LARG and nucleotide-bound Rho isoforms, but not Rac1 or Cdc42. We further show that epidermal growth factor or FBS stimulation induces association of endogenous RSK2 with LARG and LARG with RhoA. In response to these stimuli, RSK2 phosphorylates LARG at Ser1288 and thereby activates RhoA. Phosphorylation of RSK2 at threonine 577 is essential for activation of LARG-RhoA. Moreover, RSK2-mediated motility signaling depends on RhoA and -B, but not RhoC. These results establish a unique RSK2-dependent LARG-RhoA signaling module as a central organizer of directed cell migration and invasion.

Peptidyl-tRNA hydrolase 2 (PTRH2) regulates integrin-mediated pro-survival and apoptotic signaling. PTRH2 is critical in muscle development and regulates myogenic differentiation. In humans a biallelic mutation in the PTRH2 gene causes infantile-onset multisystem disease with progressive muscle weakness. We report here that the Ptrh2 knockout mouse model recapitulates the progressive congenital muscle pathology observed in patients. Ptrh2 null mice demonstrate multiple degenerating and regenerating muscle fibers, increased central nuclei, elevated creatine kinase activity and endomysial fibrosis. This progressive muscle pathology resembles the muscular dystrophy phenotype in humans and mice lacking the α7 integrin. We demonstrate that in normal muscle Ptrh2 associates in a complex with the α7β1 integrin at the sarcolemma and Ptrh2 expression is decreased in α7 integrin null muscle. Furthermore, Ptrh2 expression is altered in skeletal muscle of classical congenital muscular dystrophy mouse models. Ptrh2 levels were up-regulated in dystrophin deficient mdx muscle, which correlates with the elevated levels of the α7β1 integrin observed in mdx muscle and Duchenne muscular dystrophy patients. Similar to the α7 integrin, Ptrh2 expression was decreased in laminin-α2 dyW null gastrocnemius muscle. Our data establishes a PTRH2 mutation as a novel driver of congenital muscle degeneration and identifies a potential novel target to treat muscle myopathies.

The Myomatrix 2012 conference held April 22–24th, 2012 at the University of Nevada, Reno convened 73 international participants to discuss the dynamic relationship between muscle and its matrix in muscular dystrophy with a specific focus on congenital muscular dystrophy. Seven sessions over 2½ days defined three central themes: (1) the role of extracellular matrix proteins and compartments in development and specifically in congenital muscular dystrophy (CMD) (2) the role of extracellular matrix signaling and adhesion to membrane receptors and (3) the balance and interplay between inflammation and fibrosis as drivers of altered matrix stiffness, impaired regeneration and progressive dystrophy. This report highlights major conference findings and the translational roadmap as defined by conference attendees.

In glioblastoma (GBM), infiltration of primary tumor cells into the normal tissue and dispersal throughout the brain is a central challenge to successful treatment that remains unmet. Indeed, patients respond poorly to the current therapies of tumor resection followed by chemotherapy with radiotherapy and have only a 16-month median survival. It is therefore imperative to develop novel therapies. RSK2 is a kinase that regulates proliferation and adhesion and can promote metastasis. We demonstrate that active RSK2 regulates GBM cell adhesion and is essential for cell motility and invasion of patient-derived GBM neurospheres. RSK2 control of adhesion and migration is mediated in part by its effects on integrin-Filamin A complexes. Importantly, inhibition of RSK2 by either RSK inhibitors or shRNA silencing impairs invasion and combining RSK2 inhibitors with temozolomide improves efficacy in vitro. In agreement with the in vitro data, using public datasets, we find that RSK2 is significantly upregulated in vivo in human GBM patient tumors, and that high RSK2 expression significantly correlates with advanced tumor stage and poor patient survival. Together, our data provide strong evidence that RSK inhibitors could enhance the effectiveness of existing GBM treatment, and support RSK2 targeting as a promising approach for novel GBM therapy.

Background: RSK2 alters cell migration and metastasis, but the mechanism is incompletely understood. Results: RSK2 inactivates integrins, increases filamin binding to integrin tails, alters actin distribution, increases migration, and decreases fibronectin matrix assembly. Conclusion: RSK2 mediates inactivation of integrins and thus modulates integrin functions. Significance: These findings provide a novel mechanism by which RSK2 affects migration and may lead to more selective ways to inhibit RSK2-dependent metastasis., Modulation of integrin activation is important in many cellular functions including adhesion, migration, and assembly of the extracellular matrix. RSK2 functions downstream of Ras/Raf and promotes tumor cell motility and metastasis. We therefore investigated whether RSK2 affects integrin function. We report that RSK2 mediates Ras/Raf inactivation of integrins. As a result, we find that RSK2 impairs cell adhesion and integrin-mediated matrix assembly and promotes cell motility. Active RSK2 appears to affect integrins by reducing actin stress fibers and disrupting focal adhesions. Moreover, RSK2 co-localizes with the integrin activator talin and is present at integrin cytoplasmic tails. It is thereby in a position to modulate integrin activation and integrin-mediated migration. Activation of RSK2 promotes filamin phosphorylation and binding to integrins. We also find that RSK2 is activated in response to integrin ligation to fibronectin. Thus, RSK2 could participate in a feedback loop controlling integrin function. These results reveal RSK2 as a key regulator of integrin activity and provide a novel mechanism by which it may promote cell migration and cancer metastasis.

The small GTPase H-Ras is a proto-oncogene that activates a variety of different pathways including the extracellular-signal-regulated kinase (ERK)/mitogen-activated protein kinase pathway. H-Ras is mutated in many human malignancies, and these mutations cause the protein to be constitutively active. Phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) blocks ERK-dependent gene transcription and inhibits proliferation by sequestering ERK in the cytoplasm. We therefore investigated whether PEA-15 influences H-Ras-mediated transformation. We found that PEA-15 does not block H-Ras-activated proliferation when H-Ras is constitutively active. We show instead that in H-Ras-transformed mouse kidney epithelial cells, co-expression of PEA-15 resulted in enhanced soft agar colony growth and increased tumor growth in vivo. Overexpression of both H-Ras and PEA-15 resulted in accelerated G1/S cell cycle transition and increased activation of the ERK signaling pathway. PEA-15 mediated these effects through activation of its binding partner phospholipase D1 (PLD1). Inhibition of PLD1 or interference with PEA-15/PLD1 binding blocked PEA-15's ability to increase ERK activation. Our findings reveal a novel mechanism by which PEA-15 positively regulates Ras/ERK signaling and increases the proliferation of H-Ras-transformed epithelial cells through enhanced PLD1 expression and activation. Thus, our work provides a surprising mechanism by which PEA-15 augments H-Ras-driven transformation. These data reveal that PEA-15 not only suppresses ERK signaling and tumorigenesis but also alternatively enhances tumorigenesis in the context of active Ras.

Loss of properly regulated cell death and cell survival pathways can contribute to the development of cancer and cancer metastasis. Cell survival signals are modulated by many different receptors, including integrins. Bit-1 is an effector of anoikis (cell death due to loss of attachment) in suspended cells. The anoikis function of Bit-1 can be counteracted by integrin-mediated cell attachment. Here, we explored integrin regulation of Bit-1 in adherent cells. We show that knockdown of endogenous Bit-1 in adherent cells decreased cell survival and re-expression of Bit-1 abrogated this effect. Furthermore, reduction of Bit-1 promoted both staurosporine and serum-deprivation induced apoptosis. Indeed knockdown of Bit-1 in these cells led to increased apoptosis as determined by caspase-3 activation and positive TUNEL staining. Bit-1 expression protected cells from apoptosis by increasing phospho-IκB levels and subsequently bcl-2 gene transcription. Protection from apoptosis under serum-free conditions correlated with bcl-2 transcription and Bcl-2 protein expression. Finally, Bit-1-mediated regulation of bcl-2 was dependent on focal adhesion kinase, PI3K, and AKT. Thus, we have elucidated an integrin-controlled pathway in which Bit-1 is, in part, responsible for the survival effects of cell-ECM interactions.

Interest has emerged in the therapeutic potential of inhibiting store operated calcium (Ca

Cells respond to their environment by relaying mechanical force into biochemical stimuli that activate intracellular signal transduction pathways. Subjecting cells to in vitro mechanical stretch can mimic cellular responses to changes in the rigidity of the extracellular matrix. Here we describe an in vitro model system that mimics stretch overload in vivo. In this stretch-mediated hypertrophy model, adult rat cardiomyocytes attached to laminin-coated flexible membranes are subjected to cyclic mechanical stretch at an extension level of 10 % at 30 cycles/min. At various time points VEGF secretion into the media is collected and quantitated.

The chromatin immunoprecipitation (ChIP) assay is a versatile technique used to evaluate the association of proteins with specific DNA regions both in vivo and in vitro. This assay can be used to identify proteins associated with a specific region of the genome, or the opposite, to identify the many regions of the genome associated with a particular protein. The ChIP assay can also be used to analyze binding of transcription factors, transcription cofactors, DNA replication factors, and DNA repair proteins. Here we describe a useful ChIP-qPCR protocol to examine the interaction of NFkB with the VEGF promoter in adult rat primary cardiomyocytes that have been mechanically stretched after attaching to the extracellular matrix protein laminin.

Muscle differentiation requires a complex signaling cascade that leads to the production of multinucleated myofibers. Genes regulating the intrinsic mitochondrial apoptotic pathway also function in controlling cell differentiation. How such signaling pathways are regulated during differentiation is not fully understood. Bit‐1 (also known as PTRH2 ) mutations in humans cause infantile‐onset multisystem disease with muscle weakness. We demonstrate here that Bit‐1 controls skeletal myogenesis through a caspase‐mediated signaling pathway. Bit‐1 ‐null mice exhibit a myopathy with hypotrophic myofibers. Bit‐1 ‐null myoblasts prematurely express muscle‐specific proteins. Similarly, knockdown of Bit‐1 expression in C2C12 myoblasts promotes early differentiation, whereas overexpression delays differentiation. In wild‐type mice, Bit‐1 levels increase during differentiation. Bit‐1 ‐null myoblasts exhibited increased levels of caspase 9 and caspase 3 without increased apoptosis. Bit‐1 re‐expression partially rescued differentiation. In Bit‐1 ‐null muscle, Bcl‐2 levels are reduced, suggesting that Bcl‐2‐mediated inhibition of caspase 9 and caspase 3 is decreased. Bcl‐2 re‐expression rescued Bit‐1‐mediated early differentiation in Bit‐1 ‐null myoblasts and C2C12 cells with knockdown of Bit‐1 expression. These results support an unanticipated yet essential role for Bit‐1 in controlling myogenesis through regulation of Bcl‐2.

The chromatin immunoprecipitation (ChIP) assay is a versatile technique used to evaluate the association of proteins with specific DNA regions both in vivo and in vitro. This assay can be used to identify proteins associated with a specific region of the genome, or the opposite, to identify the many regions of the genome associated with a particular protein. The ChIP assay can also be used to analyze binding of transcription factors, transcription cofactors, DNA replication factors, and DNA repair proteins. Here we describe a useful ChIP-qPCR protocol to examine the interaction of NFkB with the VEGF promoter in adult rat primary cardiomyocytes that have been mechanically stretched after attaching to the extracellular matrix protein laminin.

Cells respond to their environment by relaying mechanical force into biochemical stimuli that activate intracellular signal transduction pathways. Subjecting cells to in vitro mechanical stretch can mimic cellular responses to changes in the rigidity of the extracellular matrix. Here we describe an in vitro model system that mimics stretch overload in vivo. In this stretch-mediated hypertrophy model, adult rat cardiomyocytes attached to laminin-coated flexible membranes are subjected to cyclic mechanical stretch at an extension level of 10 % at 30 cycles/min. At various time points VEGF secretion into the media is collected and quantitated.

Malignant gliomas are one of the most aggressive and deadly forms of cancer and can affect any age group. In glioblastoma multiforme (GBM), infiltration of primary tumor cells into the normal tissue and dispersal throughout the brain is a central challenge to successful treatment that remains unmet. Patients with malignant gliomas respond poorly to the standard therapeutic regimen of radiotherapy and chemotherapy that follow tumor resection and have only a 16-month median survival. It is therefore imperative to identify new approaches to specifically attack GBM cell survival, proliferation and invasion. The cellular mechanisms driving GBM-mediated migration and invasion are not fully understood. RSK2 (p90 ribosomal S6 kinase 2) is a kinase that regulates proliferation and adhesion and can promote metastasis. We find that RSK2 is significantly upregulated in vivo in human GBM patient tumors, and that high RSK2 expression significantly correlates with advanced tumor stage and poor patient survival. We demonstrate that active RSK2 regulates GBM adhesion and is essential for cell motility and invasion of patient-derived GBM neurospheres. Importantly, inhibition of RSK2 by either RSK inhibitors or shRNA silencing impairs invasion and combining RSK2 inhibitors with temozolomide improves efficacy in vitro. We further show that the effects of RSK2 on GBM invasion are mediated in part through activation of Rho GTPases. Rho family of GTPases are key regulators of cell polarity, migration and invasion. Here, we identify Rho A, B and C as downstream effectors of (RSK2) in GBM cell migration and invasion. Here, we identified a unique signaling pathway in which RSK2 confers invasiveness through leukemia-associated RhoGEF (LARG)-dependent Rho GTPase activation. RSK2 directly interacts with LARG and nucleotide-bound Rho isoforms, but not Rac1 and Cdc42. Our data support a fundamental importance of residue of Thr577 to the invasive signaling of RSK2. The invasive signaling of RSK2 appears to depend on RhoA and B, but not RhoC. RSK2 activates RhoA through activation of LARG by phosphorylation at Ser1288. Intriguingly, LARG activity is only required for RSK2-T577E, but not RSK2-Y707A-mediated RhoA activation and cell invasion. This further supports a pivotal role of Thr577 in invasive RSK2 signaling. These results establish a unique RSK2-dependent LARG-Rho signaling cascade as an uncompensated factor key to GBM cell migration and invasion. Together, our data provide strong evidence that RSK inhibitors could enhance the effectiveness of existing GBM treatment, and support RSK2 targeting as a promising approach for novel GBM therapy. Citation Format: Geng-Xian Shi, Ling Jin, Michelle L. Matter, Santosh Kesari, Joe W. Ramos. RSK2 provokes invasive signaling in glioblastoma through LARG-dependent activation of Rho GTPases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1363. doi:10.1158/1538-7445.AM2017-1363

Background/objectivesSepsis is a severe systemic response to infection with a high mortality rate. A higher incidence has been reported for older people, in persons with a compromised immune system including cancer patients, and in ethnic minorities. We analyzed sepsis mortality and its predictors by ethnicity in the Multiethnic Cohort (MEC).Subjects/methodsAmong 191,561 white, African American, Native Hawaiian, Japanese American, and Latino cohort members, 49,347 deaths due to all causes and 345 deaths due to sepsis were recorded during follow-up from 1993-96 until 2010. Cox proportional hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated and adjusted for relevant confounders. In addition, national death rates were analyzed to compare mortality by state.ResultsAge-adjusted rates of sepsis death were 5-times higher for Hawaii than Los Angeles (14.4 vs. 2.7 per 100,000). By ethnicity, Native Hawaiians had the highest rate in Hawaii (29.0 per 100,000) and African Americans in Los Angeles (5.2 per 100,000). In fully adjusted models, place of residence was the most important predictor of sepsis mortality (HR = 7.18; 95%CI: 4.37-11.81 Hawaii vs. Los Angeles). African Americans showed the highest risk (HR = 2.08; 95% CI: 1.16-3.75) followed by Native Hawaiians (HR = 1.88; 95% CI: 1.34-2.65) as compared to whites. Among cohort members with cancer (N = 49,794), the 2-fold higher sepsis mortality remained significant in Native Hawaiians only. The geographic and ethnic differences in the MEC agreed with results for national death data.ConclusionsThe finding that African Americans and Native Hawaiians experience a higher mortality risk due to sepsis than other ethnic groups suggest ethnicity-related biological factors in the predisposition of cancer patients and other immune-compromising conditions to develop sepsis, but regional differences in health care access and death coding may also be important.

OBJECTIVE: To identify the cause of a so-far unreported phenotype of infantile-onset multisystem neurologic, endocrine, and pancreatic disease (IMNEPD). METHODS: We characterized a consanguineous family of Yazidian-Turkish descent with IMNEPD. The two affected children suffer from intellectual disability, postnatal microcephaly, growth retardation, progressive ataxia, distal muscle weakness, peripheral demyelinating sensorimotor neuropathy, sensorineural deafness, exocrine pancreas insufficiency, hypothyroidism, and show signs of liver fibrosis. We performed whole-exome sequencing followed by bioinformatic analysis and Sanger sequencing on affected and unaffected family members. The effect of mutations in the candidate gene was studied in wild-type and mutant mice and in patient and control fibroblasts. RESULTS: In a consanguineous family with two individuals with IMNEPD, we identified a homozygous frameshift mutation in the previously not disease-associated peptidyl-tRNA hydrolase 2 (PTRH2) gene. PTRH2 encodes a primarily mitochondrial protein involved in integrin-mediated cell survival and apoptosis signaling. We show that PTRH2 is highly expressed in the developing brain and is a key determinant in maintaining cell survival during human tissue development. Moreover, we link PTRH2 to the mTOR pathway and thus the control of cell size. The pathology suggested by the human phenotype and neuroimaging studies is supported by analysis of mutant mice and patient fibroblasts. INTERPRETATION: We report a novel disease phenotype, show that the genetic cause is a homozygous mutation in the PTRH2 gene, and demonstrate functional effects in mouse and human tissues. Mutations in PTRH2 should be considered in patients with undiagnosed multisystem neurologic, endocrine, and pancreatic disease.

Integrin-mediated cell adhesion is necessary for the survival of many cell types, and loss of adhesion causes apoptosis. We have previously shown that the alpha5beta1 integrin supports cell survival on fibronectin and increases Bcl-2 protein expression. Here we show that bcl-2 transcription is elevated in cells that attach to fibronectin through alpha(v)beta1 or to vitronectin through alpha(v)beta3 but is not elevated in cells attaching through the alpha(v)beta1 integrin. Bcl-2 protein expression and protection from apoptosis under serum-free conditions correlated with bcl-2 transcription. This integrin-mediated regulation of bcl-2 is Shc- and FAK-dependent, and activation of Ras by FAK is required. Furthermore, Ras mediates this up-regulation of bcl-2 by activating the phosphatidylinositol 3-kinase-AKT pathway. Mitogen-activated protein kinase did not appear to be necessary for the activation of bcl-2 transcription. Therefore, our work characterizes the pathway that mediates the effect of integrins on bcl-2 transcription and cell survival.

The tyrosine kinase called pp125FAK is believed to play an important role in integrin-mediated signal transduction. pp125FAK is associated both functionally and spatially with integrins, which are the cell surface receptors for extracellular matrix components. Although the precise function of pp125FAK is not known, two possibilities have been proposed: pp125FAK may regulate the assembly of focal adhesions in spreading or migrating cells, or pp125FAK may participate in a signal transduction cascade to inform the nucleus that the cell is anchored. To test these models in living cells, a peptide representing the focal adhesion kinase (FAK)-binding site of the beta 1 tail was coupled to carrier protein and injected into cultured cells to competitively inhibit the binding of pp125FAK to endogenous integrin, thus inhibiting activation of pp125FAK on a cell-by-cell basis. In addition, an antibody directed against an epitope adjacent to the focal adhesion targeting sequence on pp125FAK was microinjected, as an alternative means of inhibiting pp125FAK activation. It was observed that when rounded cells were injected with either the integrin peptide or the anti-FAK antibody, the cells rapidly began to apoptose, within 4 h after injection. These results indicate that pp125FAK may play a critical role in suppressing apoptosis in fibroblasts.

Basement membrane-adherent type II alveolar cells isolated from lung assemble into lumen-containing cellular spheres which retain the correct polarity and thereby approximate the earliest fetal stage of alveolar morphogenesis. The molecular basis of this process, determined in initial experiments to be attributable mainly to the large heterotrimeric glycoprotein laminin, was probed with laminin proteolytic fragments, antibodies, and synthetic peptides. The carboxy-terminal fragment E8, but not equimolar amounts of fragment P1, blocked alveolar formation. To pursue this observation, we used several anti-E8 antibodies and identified one, prepared against A chain residues 2179-2198 ("SN-peptide") from the first loop of the G domain, as inhibitory. These results were confirmed by use of SN-peptide alone and further defined by trypsin digestion of SN-peptide to the sequence SINNNR. This conserved site promoted divalent cation dependent adhesion of both type II alveolar and HT1080 cells, was inhibitable with equimolar amounts of fragment E8 but not P1, and derives from a form of laminin present in fetal alveolar basement membranes. These studies point to an important novel cell adhesion site in the laminin E8 region with a key role in lung alveolar morphogenesis.

The molecular mechanisms regulating vascular barrier integrity remain incompletely elucidated. We have previously reported an association between the GTPase R-Ras and repeat 3 of Filamin A (FLNa). Loss of FLNa has been linked to increased vascular permeability. We sought to determine whether FLNa’s association with R-Ras affects endothelial barrier function. We report that in endothelial cells endogenous R-Ras interacts with endogenous FLNa as determined by co-immunoprecipitations and pulldowns with the FLNa-GST fusion protein repeats 1–10. Deletion of FLNa repeat 3 (FLNa 3) abrogated this interaction. In these cells FLNa and R-Ras co-localize at the plasma membrane. Knockdown of R-Ras and/or FLNa by siRNA promotes vascular permeability, as determined by TransEndothelial Electrical Resistance and FITC-dextran transwell assays. Re-expression of FLNa restored endothelial barrier function in cells lacking FLNa whereas re-expression of FLNaΔ3 did not. Immunostaining for VE-Cadherin in cells with knocked down R-Ras and FLNa demonstrated a disorganization of VE-Cadherin at adherens junctions. Loss of R-Ras and FLNa or blocking R-Ras function via GGTI-2133, a selective R-Ras inhibitor, induced vascular permeability and increased phosphorylation of VE-Cadherin (Y731) and Src (Y416). Expression of dominant negative R-Ras promoted vascular permeability that was blocked by the Src inhibitor PP2. These findings demonstrate that maintaining endothelial barrier function is dependent upon active R-Ras and association between R-Ras and FLNa and that loss of this interaction promotes VE-Cadherin phosphorylation and changes in downstream effectors that lead to endothelial leakiness.

Research on biofilms has benefited from the development of powerful new techniques to investigate their structure, function and morphology. Conjugated lectins combined with microbubbles and high-frequency ultrasound provides unique possibilities to obtain quantitative information on biofilm properties. High-frequency time-resolved scanning acoustic microscopy (SAM) offers a novel means to obtain the structural and material properties of biofilms. Noninvasive measurements were conducted by employing a high-frequency time-resolved scanning acoustic microscope operating at a center frequency of 100 MHz. Fluorescently labeled lectins were used in combination with targeted microbubbles, epifluorescence microscopy and time-resolved SAM for visualization and characterization of carbohydrate-containing extracellular polymeric substances (EPS) in the biofilms of Pseudomonas aeruginosa. In addition, ultrasonic reflectivity and transmission experiments were performed on biofilms alone and biofilms with targeted ultrasound contrast agents (UCA) in a water tank at frequencies ranging from 1 to 15 MHz. This data provides measurements of the reflection and transmission coefficients, over a broad frequency spectrum for a range of biofilm growth stages in both the presence and absence of targeted UCA.

Research on biofilms has benefited from the development of new techniques to investigate their structure, function and morphology. Conjugated lectins combined with targeted ultrasound contrast agents (UCAs) and highfrequency ultrasound, offer unique possibilities to obtain quantitative information on biofilm mechanical properties. High-frequency time-resolved scanning acoustic microscopy (SAM) provides a novel means to obtain the structural and material properties of microbial biofilms. Noninvasive measurements were conducted by employing a high-frequency timeresolved scanning acoustic microscope operating at a center frequency of 100 MHz. Fluorescently labeled lectins were used in conjunction with targeted UCAs, epifluorescence microscopy, confocal laser scanning microscopy (CLSM) and timeresolved SAM for visualization and characterization of carbohydrate- containing extracellular polymeric substances (EPS) of biofilms.

The endothelin axis promotes vasoconstriction, suggesting that antagonists of endothelin signaling might be useful in treatment of heart failure. However, promising results from animal trials have not been recapitulated in heart failure patients. Here we review the role of major signaling pathways in the heart that are involved in cell survival initiated by ET-1. These pathways include mitogen-activated protein kinase, phosphatidyl inositol-1,4,5-triphosphate kinase (PI3K-AKT), nuclear factor-kappaB (NF-kappaB), and calcineurin signaling. A better understanding of endothelin-mediated signaling in cardiac cell survival may allow a reevaluation of endothelin receptor antagonists (ETRAs) in the treatment of heart failure.

The ERK pathway responds to extracellular stimuli and oncogenes by modulating cellular processes, including transcription, adhesion, survival, and proliferation. ERK has diverse substrates that carry out these functions. The processes that are modulated are determined in part by the substrates that ERK phosphorylates. We demonstrate that PEA-15 (phosphoprotein enriched in astrocytes, 15 kDa) targets ERK to RSK2 and thereby enhances RSK2 activation. PEA-15 independently bound ERK and RSK2 and increased ERK association with RSK2 in a concentration-dependent manner. PEA-15 increased RSK2 activity and CREB-mediated transcription, and this process was regulated by phosphorylation of PEA-15. Finally, phorbol ester stimulation of PEA-15-null lymphocytes resulted in impaired RSK2 activation that was rescued by exogenous PEA-15 expression. Therefore, PEA-15 functions as a scaffold to enhance ERK activation of RSK2, and this activity is regulated by phosphorylation. Thus, PEA-15 can integrate signal transduction to provide a specific physiological outcome from activation of the multipotent ERK MAP kinase pathway.

Many proteins involved in cell-cell and cell-matrix adhesion are regulated by signal transduction pathways and can activate signal transduction on ligation. Adhesion-related signal transduction is important throughout development, hemostasis, immunity, and in diseases such as cancer. Therefore, the identification of the various signaling pathways that are involved is crucial. Expression cloning is an unbiased way to isolate proteins with specific biological functions. This methodology has been adapted for the identification of proteins involved in cell signaling pathways that are mediated by cell-cell and cell-matrix interactions. We have successfully developed and used a novel expression cloning strategy to isolate the integrin-regulated apoptosis signaling protein BIT-1. This screen was based on previous observations that integrin-mediated adhesion upregulates the anti-apoptotic protein bcl-2. Our strategy described in this chapter uses flow cytometry and a reporter construct in which the bcl-2 promoter is linked to enhanced green fluorescence protein. The advantage of using flow cytometry in expression cloning is that it increases the sensitivity of the screen by enabling us to examine function quantitatively at the level of a single cell millions of times in one experiment. The following protocol provides a detailed method for the isolation of proteins that are regulated by cell adhesion.

Many proteins involved in cell-cell and cell-matrix adhesion are regulated by signal transduction pathways and can activate signal transduction on ligation. Adhesion-related signal transduction is important throughout development, hemostasis, immunity, and in diseases such as cancer. Therefore, the identification of the various signaling pathways that are involved is crucial. Expression cloning is an unbiased way to isolate proteins with specific biological functions. This methodology has been adapted for the identification of proteins involved in cell signaling pathways that are mediated by cell-cell and cell-matrix interactions. We have successfully developed and used a novel expression cloning strategy to isolate the integrin-regulated apoptosis signaling protein BIT-1. This screen was based on previous observations that integrin-mediated adhesion upregulates the anti-apoptotic protein bcl-2. Our strategy described in this chapter uses flow cytometry and a reporter construct in which the bcl-2 promoter is linked to enhanced green fluorescence protein. The advantage of using flow cytometry in expression cloning is that it increases the sensitivity of the screen by enabling us to examine function quantitatively at the level of a single cell millions of times in one experiment. The following protocol provides a detailed method for the isolation of proteins that are regulated by cell adhesion.

Using expression cloning one can isolate proteins with specific biological functions. This methodology can be adapted for the identification of novel players in the regulation of cell signaling. Here, we describe an expression cloning strategy to identify suppressors of Ras signaling. This screen is based on the observation that the activation of the small guanosine triphosphate (GTP)-binding protein H-Ras initiates a mitogen-activated protein kinase (MAPK)-dependent signaling pathway that inactivates integrin ligand binding. Our strategy depends on flow cytometry and a monoclonal antibody that recognizes integrin activation states. Flow cytometry enhances the screen's sensitivity thereby allowing us to examine function quantitatively at the level of a single cell millions of times in one screen. The following protocol provides a detailed method for the isolation of proteins that regulate cell signaling.

The amyloid-beta peptide (Abeta) can mediate cell attachment by binding to beta1 integrins through an arg-his-asp sequence. We show here that the alpha5beta1 integrin, a fibronectin receptor, is an efficient binder of Abeta, and mediates cell attachment to nonfibrillar Abeta. Cells engineered to express alpha5beta1 internalized and degraded more added Abeta1-40 than did alpha5beta1-negative control cells. Deposition of an insoluble Abeta1-40 matrix around the alpha5beta1-expressing cells was reduced, and the cells showed less apoptosis than the control cells. Thus, the alpha5beta1 integrin may protect against Abeta deposition and toxicity, which is a course of Alzheimer's disease lesions.

Cell adhesion to amino acids 2179-2198 (SN-peptide) of the laminin-1 alpha1-chain is required for lung alveolar formation in vitro (M. L. Matter and G. W. Laurie. J. Cell Biol. 124: 1083-1090, 1994). The nature of the SN-peptide receptor(s) was probed with neutralizing anti-integrin monoclonal antibodies (MAb), cells lacking integrin subunits, soluble heparin, and SN-peptide columns. Cell adhesion and spreading studies confirmed the specificity of SN-peptide and revealed adhesion to be unaffected by inclusion of anti-beta1-, anti-alpha(2-6)- or anti-alpha(V)beta5-integrin MAb. Cells lacking beta1- or alpha6-integrin subunits were fully adherent. Adhesion was heparin, but not chondroitin sulfate or heparinase, sensitive, much as is alpha-dystroglycan-laminin-1 binding. Heparin eluted approximately 155- and 180-kDa cell-surface proteins from SN-peptide columns. An additional approximately 91-kDa protein was eluted by EDTA. All were unrecognized by anti-beta1-integrin MAb. SN-peptide therefore interacts with three cell-surface proteins for which the identity remains to be determined.