المؤلفون: Zhanna Lipatova, Andrei A. Tokarev, Geetanjali Sundaram, Nava Segev, Yongheng Liang, David Taussig, Jonathan W. Mulholland

المصدر: Traffic. 10:1831-1844

مصطلحات موضوعية: Models, Molecular, Saccharomyces cerevisiae Proteins, Protein subunit, Molecular Sequence Data, Vesicular Transport Proteins, Plasma protein binding, Biochemistry, Article, symbols.namesake, Structural Biology, Two-Hybrid System Techniques, Genetics, Amino Acid Sequence, Molecular Biology, Peptide sequence, chemistry.chemical_classification, Sequence Homology, Amino Acid, biology, Cell Biology, Golgi apparatus, Yeast, Amino acid, Cell biology, TRAPP complex, chemistry, symbols, biology.protein, Rab, Protein Binding

الوصف: TRAPP is a multi-subunit complex that acts as a Ypt/Rab activator at the Golgi apparatus. TRAPP exists in two forms: TRAPP I is comprised of five essential and conserved subunits and TRAPP II contains two additional essential and conserved subunits, Trs120 and Trs130. Previously, we have shown that Trs65, a nonessential fungi-specific TRAPP subunit, plays a role in TRAPP II assembly. TRS33 encodes another nonessential but conserved TRAPP subunit whose function is not known. Here, we show that one of these two subunits, nonessential individually, is required for TRAPP II assembly. Trs33 and Trs65 share sequence, intra-cellular localization and interaction similarities. Specifically, Trs33 interacts genetically with both Trs120 and Trs130 and physically with Trs120. In addition, trs33 mutant cells contain lower levels of TRAPP II and exhibit aberrant localization of the Golgi Ypts. Together, our results indicate that in yeast, TRAPP II assembly is an essential process that can be accomplished by either of two related TRAPP subunits. Moreover, because humans express two Trs33 homologues, we propose that the requirement of Trs33 for TRAPP II assembly is conserved from yeast to humans.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::7d424fdb91a154bea60a9c6754b1ca6cTest
https://doi.org/10.1111/j.1600-0854.2009.00988.xTest

المؤلفون: Nava Segev, Nadya Morozova, Jonathan W. Mulholland, Yongheng Liang, Andrei A. Tokarev

المصدر: Molecular Biology of the Cell. 18:2533-2541

مصطلحات موضوعية: Saccharomyces cerevisiae Proteins, Protein subunit, Saccharomyces cerevisiae, Vesicular Transport Proteins, Golgi Apparatus, Plasma protein binding, Models, Biological, symbols.namesake, Guanine Nucleotide Exchange Factors, Molecular Biology, biology, Membrane Proteins, Articles, Cell Biology, Golgi apparatus, biology.organism_classification, Transport protein, Cell biology, Protein Subunits, Protein Transport, Phenotype, TRAPP complex, Biochemistry, rab GTP-Binding Proteins, Mutation, symbols, biology.protein, Guanine nucleotide exchange factor, Rab, Protein Binding

الوصف: The conserved modular complex TRAPP is a guanine nucleotide exchanger (GEF) for the yeast Golgi Ypt-GTPase gatekeepers. TRAPP I and TRAPP II share seven subunits and act as GEFs for Ypt1 and Ypt31/32, respectively, which in turn regulate transport into and out of the Golgi. Trs65/Kre11 is one of three TRAPP II-specific subunits. Unlike the other two subunits, Trs120 and Trs130, Trs65 is not essential for viability, is conserved only among some fungi, and its contribution to TRAPP II function is unclear. Here, we provide genetic, biochemical, and cellular evidence for the role of Trs65 in TRAPP II function. First, like Trs130, Trs65 localizes to the trans-Golgi. Second, TRS65 interacts genetically with TRS120 and TRS130. Third, Trs65 interacts physically with Trs120 and Trs130. Finally, trs65 mutant cells have low levels of Trs130 protein, and they are defective in the GEF activity of TRAPP II and the intracellular distribution of Ypt1 and Ypt31/32. Together, these results show that Trs65 plays a role in the Ypt GEF activity of TRAPP II in concert with the two other TRAPP II-specific subunits. Elucidation of the role played by Trs65 in intracellular trafficking is important for understanding how this process is coordinated with two other processes in which Trs65 is implicated: cell wall biogenesis and stress response.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::0fec5271cd8458b549208e4f17d45130Test
https://doi.org/10.1091/mbc.e07-03-0221Test

المؤلفون: Zhanna Lipatova, Jonathan W. Mulholland, Nava Segev, Ankur H. Shah, Jane J. Kim

المصدر: Molecular Biology of the Cell

مصطلحات موضوعية: Saccharomyces cerevisiae Proteins, Golgi Apparatus, GTPase, Saccharomyces cerevisiae, Biology, Endoplasmic Reticulum, 03 medical and health sciences, symbols.namesake, 0302 clinical medicine, Lysosome, Gene Expression Regulation, Fungal, medicine, Autophagy, Molecular Biology, 030304 developmental biology, 0303 health sciences, Endoplasmic reticulum, Membrane Proteins, Cell Biology, Articles, Golgi apparatus, Cell biology, Transport protein, Protein Transport, medicine.anatomical_structure, rab GTP-Binding Proteins, Membrane Trafficking, Mutation, Proteolysis, symbols, Unfolded protein response, Rab, Lysosomes, 030217 neurology & neurosurgery

الوصف: Ypt1 GTPase, in the context of an autophagy-specific module, regulates ER-phagy. Because Ypt1 is a known regulator of ER-to-Golgi transport, this means that a single Ypt/Rab can regulate two alternative transport steps from one compartment, the ER, to two different destinations, the Golgi and the autophagy pathway.
Accumulation of misfolded proteins on intracellular membranes has been implicated in neurodegenerative diseases. One cellular pathway that clears such aggregates is endoplasmic reticulum autophagy (ER-phagy), a selective autophagy pathway that delivers excess ER to the lysosome for degradation. Not much is known about the regulation of ER-phagy. The conserved Ypt/Rab GTPases regulate all membrane trafficking events in eukaryotic cells. We recently showed that a Ypt module, consisting of Ypt1 and autophagy-specific upstream activator and downstream effector, regulates the onset of selective autophagy in yeast. Here we show that this module acts at the ER. Autophagy-specific mutations in its components cause accumulation of excess membrane proteins on aberrant ER structures and induction of ER stress. This accumulation is due to a block in transport of these membranes to the lysosome, where they are normally cleared. These findings establish a role for an autophagy-specific Ypt1 module in the regulation of ER-phagy. Moreover, because Ypt1 is a known key regulator of ER-to-Golgi transport, these findings establish a second role for Ypt1 at the ER. We therefore propose that individual Ypt/Rabs, in the context of distinct modules, can coordinate alternative trafficking steps from one cellular compartment to different destinations.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::1484d74c6534006210bb0a7ffbde1d9fTest
https://pubmed.ncbi.nlm.nih.gov/23924895Test

المؤلفون: Howard Riezman, David Botstein, A Wesp, Jonathan W. Mulholland

المصدر: Molecular Biology of the Cell. 8:1481-1499

مصطلحات موضوعية: Saccharomyces cerevisiae Proteins, Genes, Fungal, Fluorescent Antibody Technique, Golgi Apparatus, Arp2/3 complex, Saccharomyces cerevisiae, macromolecular substances, Actin cytoskeleton organization, GTP Phosphohydrolases, symbols.namesake, Antibody Specificity, Cell Wall, GTP-Binding Proteins, Cytoskeleton, Molecular Biology, biology, Vesicle, Actin remodeling, Cell Biology, Golgi apparatus, Actin cytoskeleton, Cell biology, Microscopy, Electron, Secretory protein, rab GTP-Binding Proteins, Mutation, biology.protein, symbols, Research Article

الوصف: Many yeast actin cytoskeleton mutants accumulate large secretory vesicles and exhibit phenotypes consistent with defects in polarized growth. This, together with actin's polarized organization, has suggested a role for the actin cytoskeleton in the vectorial transport of late secretory vesicles to the plasma membrane. By using ultrastructural and biochemical analysis, we have characterized defects manifested by mutations in the SLA2 gene (also known as the END4 gene), previously found to affect both the organization of the actin cytoskeleton and endocytosis in yeast. Defects in cell wall morphology, accumulated vesicles, and protein secretion kinetics were found in sla2 mutants similar to defects found in act1 mutants. Vesicles that accumulate in the sla2 and act1 mutants are immunoreactive with antibodies directed against the small GTPase Ypt1p but not with antibodies directed against the homologous Sec4p found on classical "late" secretory vesicles. In contrast, the late-acting secretory mutants sec1-1 and sec6-4 are shown to accumulate anti-Sec4p-positive secretory vesicles as well as vesicles that are immunoreactive with antibodies directed against Ypt1p. The late sec mutant sec4-8 is also shown to accumulate Ypt1p-containing vesicles and to exhibit defects in actin cytoskeleton organization. These results indicate the existence of at least two classes of morphologically similar, late secretory vesicles (associated with Ypt1p+ and Sec4p+, respectively), one of which appears to accumulate when the actin cytoskeleton is disorganized.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::fad4bc74582c4c24ade3ee479861d6f2Test
https://doi.org/10.1091/mbc.8.8.1481Test