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AimsUpper tract urothelial carcinoma (UTUC) is a rare malignancy with a poor prognosis which occurs sporadically or in few cases results from a genetic disorder called Lynch syndrome. Recently, examination of microsatellite instability (MSI) has gained importance as a biomarker: MSI tumours are associated with a better response to immunomodulative therapies. Limited data are known about the prevalence of MSI in UTUC. New detection methods using the fully automated Idylla MSI Assay facilitate analysis of increased patient numbers.MethodsWe investigated the frequency of MSI in a multi-institutional cohort of 243 consecutively collected UTUC samples using standard methodology (Bethesda panel), along with immunohistochemistry of mismatch repair (MMR) proteins. The same tumour cohort was retested using the Idylla MSI Assay by Biocartis.ResultsUsing standard methodology, 230/243 tumours were detected as microsatellite stable (MSS), 4/243 tumours as MSI and 9/243 samples as invalid. In comparison, the Idylla MSI Assay identified four additional tumours as MSS, equalling 234/243 tumours; 4/243 were classified as MSI and only 5/243 cases as invalid. At the immunohistochemical level, MSI results were supported in all available cases with a loss in MMR proteins. The overall concordance between the standard and the Idylla MSI Assay was 98.35%. Time to result differed between 3 hours for Idylla MSI Assay and 2 days with the standard methodology.ConclusionOur data indicate a low incidence rate of MSI tumours in patients with UTUC. Furthermore, our findings highlight that Idylla MSI Assay can be applied as an alternative method of MSI analysis for UTUC.

SUMMARY Autotaxin (ATX; ENPP2) produces lysophosphatidic acid (LPA) that regulates multiple biological functions via cognate G protein-coupled receptors LPAR1–6. ATX/LPA promotes tumor cell migration and metastasis via LPAR1 and T cell motility via LPAR2, yet its actions in the tumor immune microenvironment remain unclear. Here, we show that ATX secreted by melanoma cells is chemorepulsive for tumor-infiltrating lymphocytes (TILs) and circulating CD8+ T cells ex vivo, with ATX functioning as an LPA-producing chaperone. Mechanistically, T cell repulsion predominantly involves Gα12/13-coupled LPAR6. Upon anti-cancer vaccination of tumor-bearing mice, ATX does not affect the induction of systemic T cell responses but, importantly, suppresses tumor infiltration of cytotoxic CD8+ T cells and thereby impairs tumor regression. Moreover, single-cell data from melanoma tumors are consistent with intratumoral ATX acting as a T cell repellent. These findings highlight an unexpected role for the pro-metastatic ATX-LPAR axis in suppressing CD8+ T cell infiltration to impede anti-tumor immunity, suggesting new therapeutic opportunities., In brief Through LPA production, ATX modulates the tumor microenvironment in autocrine-paracrine manners. Matas-Rico et al. show that ATX/LPA is chemorepulsive for T cells with a dominant inhibitory role for Gα12/13-coupled LPAR6. Upon anticancer vaccination, tumor-intrinsic ATX suppresses the infiltration of CD8+ T cells without affecting their cytotoxic quality., Graphical Abstract

Defects in GABAergic function can cause anxiety- and depression-like behaviors among other neuropsychiatric disorders. Therapeutic strategies using the transplantation of GABAergic interneuron progenitors derived from the medial ganglionic eminence (MGE) into the adult hippocampus reversed the symptomatology in multiple rodent models of interneuron-related pathologies. In turn, the lysophosphatidic acid receptor LPA has been reported to be essential for hippocampal function. Converging evidence suggests that deficits in LPA receptor signaling represent a core feature underlying comparable hippocampal dysfunction and behaviors manifested in common neuropsychiatric conditions. Here, we first analyzed the GABAergic interneurons in the hippocampus of wild-type and maLPA-null mice, lacking the LPA receptor. Our data revealed a reduction in the number of neurons expressing GABA, calcium-binding proteins, and neuropeptides such as somatostatin and neuropeptide Y in the hippocampus of maLPA-null mice. Then, we used interneuron precursor transplants to test links between hippocampal GABAergic interneuron deficit, cell-based therapy, and LPA receptor-dependent psychiatric disease-like phenotypes. For this purpose, we transplanted MGE-derived interneuron precursors into the adult hippocampus of maLPA-null mice, to test their effects on GABAergic deficit and behavioral symptoms associated with the absence of the LPA receptor. Transplant studies in maLPA-null mice showed that grafted cells were able to restore the hippocampal host environment, decrease the anxiety-like behaviors and neutralize passive coping, with no abnormal effects on motor activity. Furthermore, grafted MGE-derived cells maintained their normal differentiation program. These findings reinforce the use of cell-based strategies for brain disorders and suggest that the LPA receptor represents a potential target for interneuron-related neuropsychiatric disorders., This work was supported by grants from the Spanish Ministry of Science, Innovation and Universities, co-funded by the European Regional Development Fund (ERDF, EU), (PSI2017-82604R, to LJS; PSI2017-83408-P to CP; SAF09-07746, to MAD; PI16/01510, to GET) and Andalusian Regional Ministries of Economy, Knowledge, Business and University (SEJ-4515 -to LJS; SEJ1863 to CP) and of Health and Families (Nicolas Monardes Programme to GET).

A disintegrin and metalloprotease 10 (ADAM10) is the α-secretase for amyloid precursor protein (APP). ADAM10 cleaves APP to generate neuroprotective soluble APPα (sAPPα), which precludes the generation of Aβ, a defining feature of Alzheimer's disease (AD) pathophysiology. Reduced ADAM10 activity is implicated in AD, but the mechanisms mediating ADAM10 modulation are unclear. We find that the plasma membrane enzyme glycerophosphodiester phosphodiesterase 2 (GDE2) stimulates ADAM10 APP cleavage by shedding and inactivating reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a glycosylphosphatidylinositol (GPI)-anchored inhibitor of ADAM10. In AD, membrane-tethered RECK is highly elevated and GDE2 is abnormally sequestered inside neurons. Genetic ablation of GDE2 phenocopies increased membrane RECK in AD, which is causal for reduced sAPPα, increased Aβ, and synaptic protein loss. RECK reduction restores the balance of APP processing and rescues synaptic protein deficits. These studies identify GDE2 control of RECK surface activity as essential for ADAM10 α-secretase function and physiological APP processing. Moreover, our results suggest the involvement of the GDE2-RECK-ADAM10 pathway in AD pathophysiology and highlight RECK as a potential target for therapeutic development.

Defects in GABAergic function can cause anxiety- and depression-like behaviors among other neuropsychiatric disorders. Therapeutic strategies using the transplantation of GABAergic interneuron progenitors derived from the medial ganglionic eminence (MGE) into the adult hippocampus reversed the symptomatology in multiple rodent models of interneuron-related pathologies. In turn, the lysophosphatidic acid receptor LPA

SummaryAutotaxin (ATX) is secreted by diverse cell types to produce lysophosphatidic acid (LPA) that regulates multiple biological functions via G protein-coupled receptors LPAR1-6. ATX/LPA promotes tumor cell migration and metastasis mainly via LPAR1; however, its actions in the tumor immune microenvironment remain unclear. Here, we show that ATX secreted by melanoma cells is chemorepulsive for tumor-infiltrating lymphocytes and circulating CD8+ T cells ex vivo, with ATX functioning as an LPA-producing chaperone. Mechanistically, T-cell repulsion predominantly involves Gα12/13-coupled LPAR6. Upon anti-cancer vaccination of tumor-bearing mice, ATX does not affect the induction of systemic T-cell responses but suppresses tumor infiltration of cytotoxic CD8+ T cells and thereby impairs tumor regression. Moreover, single-cell data from patient samples are consistent with intra-tumor ATX acting as a T-cell repellent. These studies highlight an unexpected role for the pro-metastatic ATX-LPAR axis in suppressing CD8+ T-cell infiltration to impede anti-tumor immunity, suggesting new therapeutic opportunities.

BackgroundAutotaxin (ATX) is a secreted glycoprotein that hydrolyzes lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA). The expression of both ATX and LPA is elevated in most solid tumors and plasma. LPA signaling directly modulates tumor cell function and contributes to the development of the fibrotic tumor microenvironment, a mechanism by which tumors evade host immunity and impairs response to therapy. IOA-289 is a potent, orally available autotaxin inhibitor which is being developed as a novel treatment of solid tumours burdened with a high degree of fibrosis.MethodsInhibition of ATX activity in human plasma was determined by measuring reduction in LPA species as quantified by LC-MS/MS. In vitro activity on biomarkers of fibrosis was assessed using the BioMAP screen and fibroblast cell cultures. T cell migration was measured using 48-well chemotaxis chambers. PK/PD studies were performed following a single oral dose of IOA-289 in mice, and plasma LPA was used as a PD biomarker. In vivo efficacy was studied in two models of breast cancer, 4T1 and E0771. Bioinformatics used TCGA and GTEX publicly available datasets.ResultsIOA-289 inhibits plasma LPA18:2 with an IC50 of 36nM, with similar results for other LPA species. IOA-289 inhibited fibrosis relevant factors in the BioMAP phenotypic screen, including sIL-6, MCP-1, αSMA, collagen-III, and sVEGF. In further studies, IOA-289 inhibited the secretion of PAI-1 and IL-6 by stimulated fibroblasts. LPA and cancer cell conditioned media inhibited T cell chemotaxis in vitro and the effect was overcome in the presence of IOA-289. The efficacious human dose of IOA-289 was determined following PK/PD studies using plasma LPA as a biomarker of response to ATX inhibition. In vivo studies showed that IOA-289 inhibited metastasis of 4T1 cells, enhanced the infiltration of T cells into 4T1 s.c. implanted tumors and prevented the growth of primary, orthotopically implanted E0771 tumors. Bioinformatics analysis demonstrated elevated ATX expression in pancreatic cancer (PDAC), and PDAC patient plasma showed a correlation of ATX levels with CA-19-9.ConclusionsThe ATX/LPA pathway represents a novel target for anti-cancer therapy with actions on the tumor, immune cell and stromal environment. IOA-289 is a highly potent and selective inhibitor of ATX with demonstrated monotherapy activity in cancer models. Based on the mechanism of action we are investigating combinations of IOA-289 with chemotherapy, immunotherapy and novel agents in ongoing preclinical studies. An acceptable safety and PK profile support the clinical development of IOA-289 which is currently in a phase I clinical trial.Ethics ApprovalThe 4T1 study was approved by The University Claude Bernard Lyon 1 Ethics Board; approval number DR2014-38 (vM). The E0771 study was reviewed and approved by the Institutional Animal Care and Use Committee of the contract research organization (Covance, Ann Arbor, MI, USA), an AAALAC International accredited program.

GDE2 (also known as GDPD5) is a multispanning membrane phosphodiesterase with phospholipase D-like activity that cleaves select glycosylphosphatidylinositol (GPI)-anchored proteins and thereby promotes neuronal differentiation both in vitro and in vivo. GDE2 is a prognostic marker in neuroblastoma, while loss of GDE2 leads to progressive neurodegeneration in mice; however, its regulation remains unclear. Here, we report that, in immature neuronal cells, GDE2 undergoes constitutive endocytosis and travels back along both fast and slow recycling routes. GDE2 trafficking is directed by C-terminal tail sequences that determine the ability of GDE2 to cleave GPI-anchored glypican-6 (GPC6) and induce a neuronal differentiation program. Specifically, we define a GDE2 truncation mutant that shows aberrant recycling and is dysfunctional, whereas a consecutive deletion results in cell-surface retention and gain of GDE2 function, thus uncovering distinctive regulatory sequences. Moreover, we identify a C-terminal leucine residue in a unique motif that is essential for GDE2 internalization. These findings establish a mechanistic link between GDE2 neuronal function and sequence-dependent trafficking, a crucial process gone awry in neurodegenerative diseases. This article has an associated First Person interview with the first author of the paper., Summary: GDE2, a six-transmembrane GPI-specific phospholipase, undergoes constitutive endosomal recycling via newly identified sequences and a unique leucine residue in its C-terminal tail as a way to regulate neuronal differentiation.

SummaryGDE2 is a six-transmembrane glycerophosphodiesterase with phospholipase D-like activity that cleaves select glycosylphosphatidylinositol (GPI)-anchored proteins and thereby influences biological signaling cascades. GDE2 promotes neuronal differentiation cell-autonomously through glypican cleavage and is a prognostic marker in neuroblastoma, while GDE2 deficiency causes progressive neurodegeneration in mice and developmental defects in zebrafish. However, the regulation of GDE2 remains unclear. Here we show that in undifferentiated neuronal cells, GDE2 undergoes constitutive internalization and traffics back along both fast and slow recycling routes, while a small percentage is sorted to late endosomes. GDE2 trafficking is dictated by distinctive C-terminal tail sequences that determine secretion, endocytosis and recycling preference, respectively, and thereby regulate GDE2 function both positively and negatively. Our study reveals the sequence determinants of GDE2 trafficking and surface localization, and provides insight into the control of GPI-anchored protein activities with potential implications for nervous system disorders associated with impaired trafficking and beyond.

Notch signaling plays an essential role in the proliferation, differentiation and cell fate determination of various tissues, including the developing pancreas. One regulator of the Notch pathway is GDE2 (or GDPD5), a transmembrane ecto-phosphodiesterase that cleaves GPI-anchored proteins at the plasma membrane, including a Notch ligand regulator. Here we report that Gdpd5-knockdown in zebrafish embryos leads to developmental defects, particularly, impaired motility and reduced pancreas differentiation, as shown by decreased expression of insulin and other pancreatic markers. Exogenous expression of human GDE2, but not catalytically dead GDE2, similarly leads to developmental defects. Human GDE2 restores insulin expression in Gdpd5a-depleted zebrafish embryos. Importantly, zebrafish Gdpd5 orthologues localize to the plasma membrane where they show catalytic activity against GPI-anchored GPC6. Thus, our data reveal functional conservation between zebrafish Gdpd5 and human GDE2, and suggest that strict regulation of GDE2 expression and catalytic activity is critical for correct embryonic patterning. In particular, our data uncover a role for GDE2 in regulating pancreas differentiation.

et al., Lysophosphatidic acid (LPA) is an intercellular signaling lipid that regulates multiple cellular functions, acting through specific G-protein coupled receptors (LPA1–6). Our previous studies using viable Malaga variant maLPA1-null mice demonstrated the requirement of the LPA1 receptor for normal proliferation, differentiation, and survival of the neuronal precursors. In the cerebral cortex LPA1 is expressed extensively in differentiating oligodendrocytes, in parallel with myelination. Although exogenous LPA-induced effects have been investigated in myelinating cells, the in vivo contribution of LPA1 to normal myelination remains to be demonstrated. This study identified a relevant in vivo role for LPA1 as a regulator of cortical myelination. Immunochemical analysis in adult maLPA1-null mice demonstrated a reduction in the steady-state levels of the myelin proteins MBP, PLP/DM20, and CNPase in the cerebral cortex. The myelin defects were confirmed using magnetic resonance spectroscopy and electron microscopy. Stereological analysis limited the defects to adult differentiating oligodendrocytes, without variation in the NG2+ precursor cells. Finally, a possible mechanism involving oligodendrocyte survival was demonstrated by the impaired intracellular transport of the PLP/DM20 myelin protein which was accompanied by cellular loss, suggesting stress-induced apoptosis. These findings describe a previously uncharacterized in vivo functional role for LPA1 in the regulation of oligodendrocyte differentiation and myelination in the CNS, underlining the importance of the maLPA1-null mouse as a model for the study of demyelinating diseases., This work was supported by the Carlos III Health Institute, State Department of Research, Development and Innovation, Spanish Ministry of Economy and Competitiveness (Grant Numbers PI10/02514—co-funded by European Research Development Fund—, to G.E-T.; SAF2011 to IV-N); Andalusian Regional Ministries of Health (Nicolás Monardes Programme, and Grants PI0187/2008, PI0232/2007 to G.E-T.) and of Economy, Innovation, Science and Employment (CTS643 and CTS433 research group grants to G.E-T. and F.R-DF., respectively); Ramon Areces Foundation (Ramon Areces Fellowship to B.G-D.); and the National Institutes of Health (USA) (Grant Numbers MH051699 and MH01723 to J.C.).

The urokinase receptor (uPAR) is a glycosylphosphatidylinositol (GPI)-anchored protein that promotes tissue remodeling, tumor cell adhesion, migration and invasion. uPAR mediates degradation of the extracellular matrix through protease recruitment and enhances cell adhesion, migration and signaling through vitronectin binding and interactions with integrins and other receptors. Full-length uPAR is released from the cell surface, but the mechanism and functional significance of uPAR release remain obscure. Here we show that transmembrane glycerophosphodiesterase GDE3 is a GPI-specific phospholipase C that cleaves and releases uPAR with consequent loss of the proteolytic and non-proteolytic activities of uPAR. In breast cancer cells, high GDE3 expression depletes endogenous uPAR resulting in a less transformed phenotype, correlating with higher survival probability in patients. Our results establish GDE3 as a negative regulator of the uPAR signaling network and, more generally, highlight GPI-anchor hydrolysis as a cell-intrinsic mechanism to alter cell behavior.

The cell surface of virtually all cell types harbors a great variety of glycosylphosphatidylinositol (GPI)-anchored proteins with diverse biological functions. GPI-anchoring is a complex post-trans...

Autotaxin (ATX) generates the lipid mediator lysophosphatidic acid (LPA). ATX-LPA signalling is involved in multiple biological and pathophysiological processes, including vasculogenesis, fibrosis, cholestatic pruritus and tumour progression. ATX has a tripartite active site, combining a hydrophilic groove, a hydrophobic lipid-binding pocket and a tunnel of unclear function. We present crystal structures of rat ATX bound to 7α-hydroxycholesterol and the bile salt tauroursodeoxycholate (TUDCA), showing how the tunnel selectively binds steroids. A structure of ATX simultaneously harbouring TUDCA in the tunnel and LPA in the pocket, together with kinetic analysis, reveals that bile salts act as partial non-competitive inhibitors of ATX, thereby attenuating LPA receptor activation. This unexpected interplay between ATX-LPA signalling and select steroids, notably natural bile salts, provides a molecular basis for the emerging association of ATX with disorders associated with increased circulating levels of bile salts. Furthermore, our findings suggest potential clinical implications in the use of steroid drugs., Autotaxin generates the bioactive lipid lysophosphatidic acid to regulate diverse biological processes. Here, the authors identify a role for bile salts as direct allosteric inhibitors of autotaxin activity, suggesting that steroids may function as regulators of lysophosphatidic acid signalling.

Introduction Glycerophosphodiester phosphodiesterase 2 (GDE2) is a multi-pass membrane protein that promotes neuronal differentiation through the cleavage of glycosylphosphatidylinositol (GPI)-anchored proteins at the cell surface. High GDE2 expression is associated with favourable outcome in neuroblastoma, while loss of GDE2 in mice leads to neuronal pathologies similar to human neurodegenerative diseases. Thus, enhancing GDE2 activity could be an attractive therapeutic strategy for neuroblastoma and related pathologies. However, the regulation of GDE2 is poorly understood. Material and methods We employed TIRF microscopy to study GDE2 subcellular localization in neuronal cell lines. Membrane internalisation of GDE2 was detected by confocal microscopy, and confirmed biochemically by biotin labelling assays. To determine the nature of the GDE2-containg intracellular compartments, we examined co-localization of GDE2 with endosome markers by both confocal microscopy and immunoprecipitation assays. Results and discussions When expressed at relatively low levels in N1E-115, Neuro2A and SH-SY5Y neuronal cell lines, GDE2 localises to discrete membrane microdomains, as well as in high-turnover intracellular vesicles. We corroborated this intracellular trafficking by biotin labelling assays, which showed that GDE2 undergoes constitutive endocytosis and recycling back to the plasma membrane in a serum-independent manner. In addition, GDE2 was found to co-localise with well-established early-endosome markers, namely EEA1 and Rab5, indicating that GDE2 internalises from the plasma membrane. GDE2 also localised partially to Rab7-positive late endosomes, but was hardly detected in lysosomes (LAMP1, LysoTracker). Furthermore, GDE2 localised to Rab11-positive recycling endosomes, pinpointing the long recycling pathway. When co-expressed with labelled ubiquitin, GDE2 was heavily poly-ubiquitinated, which takes place non-specifically in the four cytosolic lysine residues of GDE2. Lastly, sequential truncations in the N- and C-terminal cytosolic tails of GDE2 highlighted a 10-amino acid stretch that potentially regulates intracellular trafficking. Conclusion Here we report that, in neuronal cells, GDE2 is constitutively internalised and undergoes endocytic recycling along both the short and, in particular, the long recycling pathways. This process appears to be regulated by a stretch of 10 residues in the cytosolic C-terminal tail, which could be related to non-specific ubiquitin ligation.

Neurogenesis persists in certain regions of the adult brain including the subgranular zone of the hippocampal dentate gyrus wherein its regulation is essential, particularly in relation to learning, stress and modulation of mood. Lysophosphatidic acid (LPA) is an extracellular signaling phospholipid with important neural regulatory properties mediated by specific G protein-coupled receptors, LPA(1-5). LPA(1) is highly expressed in the developing neurogenic ventricular zone wherein it is required for normal embryonic neurogenesis, and, by extension may play a role in adult neurogenesis as well. By means of the analyses of a variant of the original LPA(1)-null mutant mouse, termed the Malaga variant or "maLPA(1)-null," which has recently been reported to have defective neurogenesis within the embryonic cerebral cortex, we report here a role for LPA(1) in adult hippocampal neurogenesis. Proliferation, differentiation and survival of newly formed neurons are defective in the absence of LPA(1) under normal conditions and following exposure to enriched environment and voluntary exercise. Furthermore, analysis of trophic factors in maLPA(1)-null mice demonstrated alterations in brain-derived neurotrophic factor and insulin growth factor 1 levels after enrichment and exercise. Morphological analyses of doublecortin positive cells revealed the anomalous prevalence of bipolar cells in the subgranular zone, supporting the operation of LPA(1) signaling pathways in normal proliferation, maturation and differentiation of neuronal precursors.

Lysophosphatidic acid (LPA) is a new, intercellular signalling molecule in the brain that has an important role in adult hippocampal plasticity. Mice lacking the LPA(1) receptor exhibit motor, emotional and cognitive alterations. However, the potential relationship among these concomitant impairments was unclear. Wild-type and maLPA(1)-null mice were tested on the hole-board for habituation and spatial learning. MaLPA(1)-null mice exhibited reduced exploration in a novel context and a defective intersession habituation that also revealed increased anxiety-like behaviour throughout the hole-board testing. In regard to spatial memory, maLPA(1) nulls failed to reach the controls' performance at the end of the reference memory task. Moreover, their defective working memory on the first training day suggested a delayed acquisition of the task's working memory rule, which is also a long term memory component. The temporal interval between trials and the task's difficulty may explain some of the deficits found in these mice. Principal components analysis revealed that alterations found in each behavioural dimension were independent. Therefore, exploratory and emotional impairments did not account for the cognitive deficits that may be attributed to maLPA(1) nulls' hippocampal malfunction.

Lysophosphatidic acid (LPA) has emerged as a new regulatory molecule in the brain. Recently, some studies have shown a role for this molecule and its LPA1 receptor in the regulation of plasticity and neurogenesis in the adult brain. However, no systematic studies have been conducted to investigate whether the LPA1 receptor is involved in behavior. In this study, we studied the phenotype of maLPA1-null mice, which bear a targeted deletion at the lpa1 locus, in a battery of tests examining neurologic performance, habituation in exploratory behavior in response to low and mild anxiety environments and spatial memory. MaLPA1-null mutants showed deficits in both olfaction and somesthesis, but not in retinal or auditory functions. Sensorimotor co-ordination was impaired only in the equilibrium and grasping reflexes. The mice also showed impairments in neuromuscular strength and analgesic response. No additional differences were observed in the rest of the tests used to study sensoriomotor orientation, limb reflexes and co-ordinated limb use. At behavioral level, maLPA1-null mice showed an impaired exploration in the open field and increased anxiety-like response when exposed to the elevated plus maze. Furthermore, the mice exhibit impaired spatial memory retention and reduced use of spatial strategies in the Morris water maze. We propose that the LPA1 receptor may play a major role in both spatial memory and response to anxiety-like conditions. © 2009 Blackwell Publishing Ltd/International Behavioural and Neural Genetics Society., This work was supported by grants from the Human Frontier Science Programme (J.C., F.R.D.F.), MEC SEJ2007-61187 (L.S.), FIS 01/3032 (G.E.), FIS 02/1643, FIS PI07/0629 (G.E.), Red CIEN (G03/06) (F.R.D.F.) (Instituto de Salud Carlos III, Ministerio de Sanidad) and the National Institutes of Health (USA) MH51699 and MH01723 (J.C.).

Lysophosphatidic acid (LPA) is a simple phospholipid with extracellular signaling properties mediated by specific G protein-coupled receptors. At least 2 LPA receptors, LPA 1 and LPA 2 , are expressed in the developing brain, the former enriched in the neurogenic ventricular zone (VZ), suggesting a normal role in neurogenesis. Despite numerous studies reporting the effects of exogenous LPA using in vitro neural models, the first LPA 1 loss-of-function mutants reported did not show gross cerebral cortical defects in the 50% that survived perinatal demise. Here, we report a role for LPA 1 in cortical neural precursors resulting from analysis of a variant of a previously characterized LPA 1 -null mutant that arose spontaneously during colony expansion. These LPA 1 -null mice, termed maLPA 1 , exhibit almost complete perinatal viability and show a reduced VZ, altered neuronal markers, and increased cortical cell death that results in a loss of cortical layer cellularity in adults. These data support LPA 1 function in normal cortical development and suggest that the presence of genetic modifiers of LPA 1 influences cerebral cortical development.

Lysophosphatidic acid (LPA), a lipid mediator enriched in serum, stimulates cell migration, proliferation and other functions in many cell types. LPA acts on six known G protein-coupled receptors, termed LPA(1-6), showing both overlapping and distinct signaling properties. Here we show that, unexpectedly, LPA and serum almost completely inhibit the transwell migration of B16 melanoma cells, with alkyl-LPA(18:1) being 10-fold more potent than acyl-LPA(18:1). The anti-migratory response to LPA is highly polarized and dependent on protein kinase A (PKA) but not Rho kinase activity; it is associated with a rapid increase in intracellular cAMP levels and PIP3 depletion from the plasma membrane. B16 cells express LPA(2), LPA(5) and LPA(6) receptors. We show that LPA-induced chemorepulsion is mediated specifically by the alkyl-LPA-preferring LPA(5) receptor (GPR92), which raises intracellular cAMP via a noncanonical pathway. Our results define LPA(5) as an anti-migratory receptor and they implicate the cAMP-PKA pathway, along with reduced PIP3 signaling, as an effector of chemorepulsion in B16 melanoma cells.

Neuroblastoma is a pediatric embryonal malignancy characterized by impaired neuronal differentiation. A better understanding of neuroblastoma differentiation is essential for developing new therapeutic approaches. GDE2 (encoded by GDPD5) is a six-transmembrane-domain glycerophosphodiesterase that promotes embryonic neurogenesis. We find that high GDPD5 expression is strongly associated with favorable outcome in neuroblastoma. GDE2 induces differentiation of neuroblastoma cells, suppresses cell motility, and opposes RhoA-driven neurite retraction. GDE2 alters the Rac-RhoA activity balance and the expression of multiple differentiation-associated genes. Mechanistically, GDE2 acts by cleaving (in cis) and releasing glycosylphosphatidylinositol-anchored glypican-6, a putative co-receptor. A single point mutation in the ectodomain abolishes GDE2 function. Our results reveal GDE2 as a cell-autonomous inducer of neuroblastoma differentiation with prognostic significance and potential therapeutic value.