Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cystic fibrosis (CF) is caused by defects in the CF transmembrane conductance regulator (CFTR) that functions as a chloride channel in epithelial cells. The most common cause of CF is the abnormal trafficking of CFTR mutants. Therefore, understanding the cellular machineries that transit CFTR from the endoplasmic reticulum to the plasma membrane (PM) is important. The coat protein complex I (COPI) has been implicated in the anterograde and retrograde transport of proteins and lipids between the endoplasmic reticulum and the Golgi. Here, we investigated the role of COPI in CFTR trafficking. Blocking COPI recruitment to membranes by expressing an inactive form of the GBF1 guanine nucleotide exchange factor for ADP-ribosylation factor inhibits CFTR trafficking to the PM. Similarly, inhibiting COPI dissociation from membranes by expressing a constitutively active ADP-ribosylation factor 1 mutant arrests CFTR within disrupted Golgi elements. To definitively explore the relationship between COPI and CFTR in epithelial cells, we depleted beta-COP from the human colonic epithelial cell HT-29Cl.19A using small interfering RNA. Beta-COP depletion did not affect CFTR synthesis but impaired its trafficking to the PM. The arrest occurred pre-Golgi as shown by reduced level of glycosylation. Importantly, decreased trafficking of CFTR had a functional consequence as cells depleted of beta-COP showed decreased cAMP-activated chloride currents. To explore the mechanism of COPI action in CFTR traffic we tested whether CFTR was COPI cargo. We discovered that the alpha-, beta-, and gamma-subunits of COPI co-immunoprecipitated with CFTR. Our results indicate that the COPI complex plays a critical role in CFTR trafficking to the PM.
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PMID:Cystic fibrosis transmembrane conductance regulator trafficking is mediated by the COPI coat in epithelial cells. 1793 45

Protein trafficking through the secretory pathway plays a key role in epithelial organ development and function. The expansion of tracheal tubes in Drosophila depends on trafficking of coatomer protein complex I (COPI)-coated vesicles between the Golgi complex and the endoplasmic reticulum (ER). However, it is not clear how this pathway is regulated. Here we describe an essential function of the Sec7 domain guanine nucleotide exchange factor (GEF) gartenzwerg (garz) in epithelial tube morphogenesis and protein secretion. garz is essential for the recruitment of COPI components and for normal Golgi organization. A GFP-Garz fusion protein is distributed in the cytoplasm and accumulates at the cis-Golgi. Localization to the Golgi requires the C-terminal part of Garz. Conversely, blocking the GDP-GTP nucleotide exchange reaction leads to constitutive Golgi localization, suggesting that Garz cycles in a GEF-activity-dependent manner between cytoplasmic and Golgi-membrane-localized pools. The related human ARF-GEF protein GBF1 can substitute for garz function in Drosophila tracheal cells, indicating that the relevant functions of these proteins are conserved. We show that garz interacts genetically with the ARF1 homolog ARF79F and with the ARF1-GAP homolog Gap69C, thus placing garz in a regulatory circuit that controls COPI trafficking in Drosophila. Interestingly, overexpression of garz causes accumulation of secreted proteins in the ER, suggesting that excessive garz activity leads to increased retrograde trafficking. Thus, garz might regulate epithelial tube morphogenesis and secretion by controlling the rate of trafficking of COPI vesicles.
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PMID:The Drosophila Sec7 domain guanine nucleotide exchange factor protein Gartenzwerg localizes at the cis-Golgi and is essential for epithelial tube expansion. 2234 97

Poliovirus (PV), a model for interactions of picornaviruses with host cells, replicates its genomic RNA in association with cellular membranes. The origin of PV replication membranes has not been determined. Hypotheses about the origin of replication membranes, based largely on localization of viral proteins, include modification of coat protein complex I (COPI) and/or COPII secretory pathway vesicles and subversion of autophagic membranes. Here, we use an antibody against double-stranded RNA (dsRNA) to identify replication complexes by detection of dsRNA replication intermediates. dsRNA signal is dependent on virus genome replication and colocalizes with the viral integral membrane protein 3A, which is part of the RNA replication complex. We show that early in infection, dsRNA does not colocalize with a marker for autophagic vesicles, making it unlikely that autophagosomes contribute to the generation of PV RNA replication membranes. We also find that dsRNA does not colocalize with a marker of the COPII coat, Sec31, and, in fact, we demonstrate proteasome-dependent loss of full-length Sec31 during PV infection. These data indicate that COPII vesicles are an unlikely source of PV replication membranes. We show that the Golgi resident G-protein Arf1 and its associated guanine nucleotide exchange factor (GEF), GBF1, transiently colocalize with dsRNA early in infection. In uninfected cells, Arf1 nucleates COPI coat formation, although during infection the COPI coat itself does not colocalize with dsRNA. Phosphatidylinositol-4-phosphate, which is associated with enterovirus-induced vesicles, tightly colocalizes with Arf1/GBF1 throughout infection. Our data point to a noncanonical role for some of the COPI-generating machinery in producing unique replication surfaces for PV RNA replication. IMPORTANCE Picornaviruses are a diverse and major cause of human disease, and their genomes replicate in association with intracellular membranes. There are multiple hypotheses to explain the nature and origin of these membranes, and a complete understanding of the host requirements for membrane rearrangement would provide novel drug targets essential for viral genome replication. Here, we study the model picornavirus, poliovirus, and show that some, but not all, components of the cellular machinery required for retrograde traffic from the Golgi apparatus to the endoplasmic reticulum are transiently present at the sites of viral RNA replication. We also show that the full-length Sec31 protein, which has been suggested to be present on PV RNA replication membranes, is lost during infection in a proteasome-dependent manner. This study helps to reconcile multiple hypotheses about the origin of poliovirus replication membranes and points to known host cell protein complexes that would make likely drug targets to inhibit picornavirus infections.
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PMID:Generation of unique poliovirus RNA replication organelles. 2457 Mar 67

Candida albicans is both a major fungal pathogen and a member of the commensal human microflora. The morphological switch from yeast to hyphal growth is associated with disease and many environmental factors are known to influence the yeast-to-hyphae switch. The Ras1-Cyr1-PKA pathway is a major regulator of C. albicans morphogenesis as well as biofilm formation and white-opaque switching. Previous studies have shown that hyphal growth is strongly repressed by mitochondrial inhibitors. Here, we show that mitochondrial inhibitors strongly decreased Ras1 GTP-binding and activity in C. albicans and similar effects were observed in other Candida species. Consistent with there being a connection between respiratory activity and GTP-Ras1 binding, mutants lacking complex I or complex IV grew as yeast in hypha-inducing conditions, had lower levels of GTP-Ras1, and Ras1 GTP-binding was unaffected by respiratory inhibitors. Mitochondria-perturbing agents decreased intracellular ATP concentrations and metabolomics analyses of cells grown with different respiratory inhibitors found consistent perturbation of pyruvate metabolism and the TCA cycle, changes in redox state, increased catabolism of lipids, and decreased sterol content which suggested increased AMP kinase activity. Biochemical and genetic experiments provide strong evidence for a model in which the activation of Ras1 is controlled by ATP levels in an AMP kinase independent manner. The Ras1 GTPase activating protein, Ira2, but not the Ras1 guanine nucleotide exchange factor, Cdc25, was required for the reduction of Ras1-GTP in response to inhibitor-mediated reduction of ATP levels. Furthermore, Cyr1, a well-characterized Ras1 effector, participated in the control of Ras1-GTP binding in response to decreased mitochondrial activity suggesting a revised model for Ras1 and Cyr1 signaling in which Cyr1 and Ras1 influence each other and, together with Ira2, seem to form a master-regulatory complex necessary to integrate different environmental and intracellular signals, including metabolic status, to decide the fate of cellular morphology.
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PMID:Mitochondrial Activity and Cyr1 Are Key Regulators of Ras1 Activation of C. albicans Virulence Pathways. 2631 37