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Aging is typified by a progressive decline in mitochondrial activity and stress resilience. Here, we review how mitochondrial stress pathways have pleiotropic effects on cellular and systemic homeostasis, which can comprise protective or detrimental responses during aging. We describe recent evidence arguing that defects in these conserved adaptive pathways contribute to aging and age-related diseases. Signaling pathways regulating the mitochondrial unfolded protein response, mitochondrial membrane dynamics, and mitophagy are discussed, emphasizing how their failure contributes to heteroplasmy and de-regulation of key metabolites. Our current understanding of how these processes are controlled and interconnected explains how mitochondria can widely impact fundamental aspects of aging.

Endoplasmic reticulum (ER)-to-Golgi trafficking is an essential and highly conserved cellular process. The coat protein complex-II (COPII) arm of the trafficking machinery incorporates a wide array of cargo proteins into vesicles through direct or indirect interactions with Sec24, the principal subunit of the COPII coat. Approximately one-third of all mammalian proteins rely on the COPII-mediated secretory pathway for membrane insertion or secretion. There are four mammalian Sec24 paralogs and three yeast Sec24 paralogs with emerging evidence of paralog-specific cargo interaction motifs. Furthermore, individual paralogs also differ in their affinity for a subset of sorting motifs present on cargo proteins. As with many aspects of protein trafficking, we lack a systematic and thorough understanding of the interaction of Sec24 with cargoes. This systematic review focuses on the current knowledge of cargo binding to both yeast and mammalian Sec24 paralogs and their ER export motifs. The analyses show that Sec24 paralog specificity of cargo (and cargo receptors) range from exclusive paralog dependence or preference to partial redundancy. We also discuss how the Sec24 secretion system is hijacked by viral (e.g., VSV-G, Hepatitis B envelope protein) and bacterial (e.g., the enteropathogenic E. coli type III secretion system effector NleA/EspI) pathogens. This article is protected by copyright. All rights reserved.

Summary TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production., Graphical Abstract, Highlights • Phosphorylation of RIPK1 by MK2 acts as survival checkpoint in TNF signaling • TNF-induced activation of MK2 results in global RIPK1 phosphorylation • MK2-mediated phosphorylation suppresses RIPK1 kinase activation and cell death • Complex-II originates from RIPK1 in complex-I as well as cytosolic RIPK1, Jaco et al. show that MK2 directly phosphorylates RIPK1 at residue S321, suppressing the cytotoxic potential of RIPK1 and acting as a checkpoint within the TNF signaling pathway.

Blue light (BL) is a major environmental factor that affects the physiology, behavior, and infectivity of bacteria as it contributes to the generation of reactive oxygen species (ROS) while increasing photo-oxidative stress in cells. However, precise photo-oxidative response mechanism in non-phototrophic bacteria is yet to be elucidated. In this study, we investigated the effect of BL in Vibrio cholerae by using genetics and transcriptome profiling. Genome-wide analysis revealed that transcription of 6.3% of V. cholerae genes were regulated by BL. We further showed that BL enhances ROS production, which is generated through the oxidative phosphorylation. To understand signaling mechanisms, we generated several knockouts and analyzed their transcriptome under BL exposure. Studies with a double-knockout confirm an anti-sigma factor (ChrR) and putative metalloregulatory-like protein (MerR) are responsible for the genome-wide regulation to BL response in V. cholerae. Collectively, these results demonstrate that MerR-like proteins, in addition to ChrR, are required for V. cholerae to mount an appropriate response against photo-oxidative stress induced by BL. Outside its natural host, V. cholerae can survive for extended periods in natural aquatic environments. Therefore, the regulation of light response for V. cholerae may be a critical cellular process for its survival in these environments., Scientific and Technological Research Council of Turkey (TÜBİTAK)-TBAG

Chemical control of Septoria leaf blotch, caused by Mycosphaerella graminicola, is essential to ensure wheat yield and food security in most European countries. Mycosphaerella graminicola has developed resistance to several classes of fungicide and, with the efficacy of azoles gradually declining over time, new modes of action and/or improvements in host varietal resistance are urgently needed to ensure future sustainable disease control. Several new-generation carboxamide fungicides with broad-spectrum activity have recently been introduced into the cereal market. Carboxamides inhibit succinate dehydrogenase (Sdh) of the mitochondrial respiratory chain (complex II) but, because of their single-site specificity, these fungicides may be prone to resistance development. The objective of this study was to assess the risk of resistance development to different Sdh inhibitor (SDHI) fungicides in M. graminicola. UV mutagenesis was conducted to obtain a library of carboxin-resistant mutants. A range of SDHI resistance-conferring mutations was found in Sdh subunits B, C and D. Pathogenicity studies with a range of Sdh variants did not detect any fitness costs associated with these mutations. Most of the amino acid residues identified (e.g. B-S221P/T, B-H267F/L/N/Y, B-I269V and D-D129E/G/T) are directly involved in forming the cavity in which SDHI fungicides bind. Docking studies of SDHI fungicides in structural models of wild-type and mutated Sdh complexes also indicated which residues were important for the binding of different SDHI fungicides and showed a different binding for fluopyram. The predictive power of the model was also shown. Further diagnostic development, enabling the detection of resistant alleles at low frequencies, and cross-resistance studies will aid the implementation of anti-resistance strategies to prolong the cost-effectiveness and lifetime of SDHI fungicides.

The main trimeric light-harvesting complex of higher plants (LHCII) consists of three different Lhcb proteins (Lhcb1-3). We show that Arabidopsis thaliana T-DNA knockout plants lacking Lhcb3 (koLhcb3) compensate for the lack of Lhcb3 by producing increased amounts of Lhcb1 and Lhcb2. As in wild-type plants, LHCII-photosystem II (PSII) supercomplexes were present in Lhcb3 knockout plants (koLhcb3), and preservation of the LHCII trimers (M trimers) indicates that the Lhcb3 in M trimers has been replaced by Lhcb1 and/or Lhcb2. However, the rotational position of the M LHCII trimer was altered, suggesting that the Lhcb3 subunit affects the macrostructural arrangement of the LHCII antenna. The absence of Lhcb3 did not result in any significant alteration in PSII efficiency or qE type of nonphotochemical quenching, but the rate of transition from State 1 to State 2 was increased in koLhcb3, although the final extent of state transition was unchanged. The level of phosphorylation of LHCII was increased in the koLhcb3 plants compared with wild-type plants in both State 1 and State 2. The relative increase in phosphorylation upon transition from State 1 to State 2 was also significantly higher in koLhcb3. It is suggested that the main function of Lhcb3 is to modulate the rate of state transitions.

Chemical control of Septoria leaf blotch, caused by Mycosphaerella graminicola, is essential to ensure wheat yield and food security in most European countries. Mycosphaerella graminicola has developed resistance to several classes of fungicide and, with the efficacy of azoles gradually declining over time, new modes of action and/or improvements in host varietal resistance are urgently needed to ensure future sustainable disease control. Several new-generation carboxamide fungicides with broad-spectrum activity have recently been introduced into the cereal market. Carboxamides inhibit succinate dehydrogenase (Sdh) of the mitochondrial respiratory chain (complex II) but, because of their single-site specificity, these fungicides may be prone to resistance development. The objective of this study was to assess the risk of resistance development to different Sdh inhibitor (SDHI) fungicides in M. graminicola. UV mutagenesis was conducted to obtain a library of carboxin-resistant mutants. A range of SDHI resistance-conferring mutations was found in Sdh subunits B, C and D. Pathogenicity studies with a range of Sdh variants did not detect any fitness costs associated with these mutations. Most of the amino acid residues identified (e.g. B-S221P/T, B-H267F/L/N/Y, B-I269V and D-D129E/G/T) are directly involved in forming the cavity in which SDHI fungicides bind. Docking studies of SDHI fungicides in structural models of wild-type and mutated Sdh complexes also indicated which residues were important for the binding of different SDHI fungicides and showed a different binding for fluopyram. The predictive power of the model was also shown. Further diagnostic development, enabling the detection of resistant alleles at low frequencies, and cross-resistance studies will aid the implementation of anti-resistance strategies to prolong the cost-effectiveness and lifetime of SDHI fungicides.

Germline mutations in SDHD predispose to the development of head and neck paragangliomas, and phaeochromocytomas. The risk of developing a tumor depends on the sex of the parent who transmits the mutation: paragangliomas only arise upon paternal transmission. In this study, both the risk of paraganglioma and phaeochromocytoma formation, and the risk of developing associated symptoms were investigated in 243 family members with the SDHD. D92Y founder mutation. By using the Kaplan-Meier method, age-specific penetrance was calculated separately for paraganglioma formation as defined by magnetic resonance imaging (MRI) and for paraganglioma-related signs and symptoms. Evaluating clinical signs and symptoms alone, the penetrance reached a maximum of 57% by the age of 47 years. When MRI detection of occult paragangliomas was included, penetrance was estimated to be 54% by the age of 40 years, 68% by the age of 60 years and 87% by the age of 70 years. Multiple tumors were found in 65% and phaeochromocytomas were diagnosed in 8% of paraganglioma patients. Malignant paraganglioma was diagnosed in one patient (3%). Although the majority of carriers of a paternally inherited SDHD mutation will eventually develop head and neck paragangliomas, we find a lower penetrance than previous estimates from studies based on predominantly index cases. The family-based study described here emphasizes the importance of the identification and inclusion of clinically unaffected mutation carriers in all estimates of penetrance. This finding will allow a more accurate genetic counseling and warrants a 'wait and scan' policy for asymptomatic paragangliomas, combined with biochemical screening for catecholamine excess in SDHD-linked patients. European Journal of Human Genetics (2010) 18, 62-66; doi:10.1038/ejhg.2009.112; published online 8 July 2009

Respiratory inhibitors are among the fungicides most widely used for disease control on crops. Most are strobilurins and carboxamides, inhibiting the cytochrome b of mitochondrial complex III and the succinate dehydrogenase of mitochondrial complex II, respectively. A few years after the approval of these inhibitors for use on grapevines, field isolates of Botrytis cinerea , the causal agent of gray mold, resistant to one or both of these classes of fungicide were recovered in France and Germany. However, little was known about the mechanisms underlying this resistance in field populations of this fungus. Such knowledge could facilitate resistance risk assessment. The aim of this study was to investigate the mechanisms of resistance occurring in B. cinerea populations. Highly specific resistance to strobilurins was correlated with a single mutation of the cytb target gene. Changes in its intronic structure may also have occurred due to an evolutionary process controlling selection for resistance. Specific resistance to carboxamides was identified for six phenotypes, with various patterns of resistance levels and cross-resistance. Several mutations specific to B. cinerea were identified within the sdhB and sdhD genes encoding the iron-sulfur protein and an anchor protein of the succinate dehydrogenase complex. Another as-yet-uncharacterized mechanism of resistance was also recorded. In addition to target site resistance mechanisms, multidrug resistance, linked to the overexpression of membrane transporters, was identified in strains with low to moderate resistance to several respiratory inhibitors. This diversity of resistance mechanisms makes resistance management difficult and must be taken into account when developing strategies for Botrytis control.

Contains fulltext : 80017.pdf (Publisher’s version ) (Closed access) BACKGROUND: Phaeochromocytomas and paragangliomas are neuro-endocrine tumours that occur sporadically and in several hereditary tumour syndromes, including the phaeochromocytoma-paraganglioma syndrome. This syndrome is caused by germline mutations in succinate dehydrogenase B (SDHB), C (SDHC), or D (SDHD) genes. Clinically, the phaeochromocytoma-paraganglioma syndrome is often unrecognised, although 10-30% of apparently sporadic phaeochromocytomas and paragangliomas harbour germline SDH-gene mutations. Despite these figures, the screening of phaeochromocytomas and paragangliomas for mutations in the SDH genes to detect phaeochromocytoma-paraganglioma syndrome is rarely done because of time and financial constraints. We investigated whether SDHB immunohistochemistry could effectively discriminate between SDH-related and non-SDH-related phaeochromocytomas and paragangliomas in large retrospective and prospective tumour series. METHODS: Immunohistochemistry for SDHB was done on 220 tumours. Two retrospective series of 175 phaeochromocytomas and paragangliomas with known germline mutation status for phaeochromocytoma-susceptibility or paraganglioma-susceptibility genes were investigated. Additionally, a prospective series of 45 phaeochromocytomas and paragangliomas was investigated for SDHB immunostaining followed by SDHB, SDHC, and SDHD mutation testing. FINDINGS: SDHB protein expression was absent in all 102 phaeochromocytomas and paragangliomas with an SDHB, SDHC, or SDHD mutation, but was present in all 65 paraganglionic tumours related to multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and neurofibromatosis type 1. 47 (89%) of the 53 phaeochromocytomas and paragangliomas with no syndromic germline mutation showed SDHB expression. The sensitivity and specificity of the SDHB immunohistochemistry to detect the presence of an SDH mutation in the prospective series were 100% (95% CI 87-100) and 84% (60-97), respectively. INTERPRETATION: Phaeochromocytoma-paraganglioma syndrome can be diagnosed reliably by an immunohistochemical procedure. SDHB, SDHC, and SDHD germline mutation testing is indicated only in patients with SDHB-negative tumours. SDHB immunohistochemistry on phaeochromocytomas and paragangliomas could improve the diagnosis of phaeochromocytoma-paraganglioma syndrome. FUNDING: The Netherlands Organisation for Scientific Research, Dutch Cancer Society, Vanderes Foundation, Association pour la Recherche contre le Cancer, Institut National de la Sante et de la Recherche Medicale, and a PHRC grant COMETE 3 for the COMETE network.

Background: Mutations in genes coding for the mitochondrial complex II succinate dehydrogenase (SDH) subunits cause familial neural crest derived (NCD) tumours. Methods: Index cases from six apparently unrelated families affected by NCD tumours were analysed for mutations in the SDHB, SDHC, and SDHD genes. Results: The same nonsense germline heterozygous mutation (Q109X) in exon 4 of the SDHD gene was found in each of the six families. Overall, 43 heterozygotes were identified. These were evaluated for the presence of NCD tumours through radiological examination of the neck, thorax, and abdomen, and measurement of urinary metanephrines and plasma chromogranin A. A novel missense SDHD variant, T112I, which did not segregate with the Q109X mutation and was not associated with phenotypic manifestations, was observed in one of the families. Microsatellite analysis showed a common haplotype in all individuals heterozygous for the Q109X mutation, indicating a founder effect. Overall, 18 heterozygotes were clinically affected by at least one NCD tumour. Every affected patient inherited the germline mutation from the father, confirming SDHD maternal genomic imprinting. Penetrance of the paternally inherited mutation progressively increased from 33% to 83% at 30 and 60 years, respectively. Affected patients showed high clinical variability, ranging from monolateral to bilateral glomus tumours variably associated or not with paragangliomas or phaeochromocytomas. Loss of heterozygosity was observed in tumour cells isolated by laser capture microdissection. Conclusions: This study shows that a single founder SDHD mutation is present in an area of central Italy and that this mutation is associated with widely variable interfamilial and intrafamilial expressivity.