scholarly journals The conserved oligomeric Golgi complex is involved in double-membrane vesicle formation during autophagy

2010 ◽  
Vol 188 (1) ◽  
pp. 101-114 ◽  
Author(s):  
Wei-Lien Yen ◽  
Takahiro Shintani ◽  
Usha Nair ◽  
Yang Cao ◽  
Brian C. Richardson ◽  
...  
Keyword(s):  
Membrane Vesicle ◽  
Autophagosome Formation ◽  
Double Membrane ◽  
Complex Part ◽  
Cog Complex ◽  
Conserved Oligomeric Golgi Complex ◽  
Conserved Oligomeric Golgi ◽  
Critical Components ◽  
Molecular Components ◽  
Related Proteins

Macroautophagy is a catabolic pathway used for the turnover of long-lived proteins and organelles in eukaryotic cells. The morphological hallmark of this process is the formation of double-membrane autophagosomes that sequester cytoplasm. Autophagosome formation is the most complex part of macroautophagy, and it is a dynamic event that likely involves vesicle fusion to expand the initial sequestering membrane, the phagophore; however, essentially nothing is known about this process including the molecular components involved in vesicle tethering and fusion. In this study, we provide evidence that the subunits of the conserved oligomeric Golgi (COG) complex are required for double-membrane cytoplasm to vacuole targeting vesicle and autophagosome formation. COG subunits localized to the phagophore assembly site and interacted with Atg (autophagy related) proteins. In addition, mutations in the COG genes resulted in the mislocalization of Atg8 and Atg9, which are critical components involved in autophagosome formation.

scholarly journals Early Stages of the Secretory Pathway, but Not Endosomes, Are Required for Cvt Vesicle and Autophagosome Assembly in Saccharomyces cerevisiae

2004 ◽  
Vol 15 (5) ◽  
pp. 2189-2204 ◽  
Author(s):  
Fulvio Reggiori ◽  
Chao-Wen Wang ◽  
Usha Nair ◽  
Takahiro Shintani ◽  
Hagai Abeliovich ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Secretory Pathway ◽  
Membrane Vesicle ◽  
Endomembrane System ◽  
Vesicle Membrane ◽  
Double Membrane ◽  
Vesicle Biogenesis ◽  
Molecular Components ◽  
Vacuolar Trafficking

The Cvt pathway is a biosynthetic transport route for a distinct subset of resident yeast vacuolar hydrolases, whereas macroautophagy is a nonspecific degradative mechanism that allows cell survival during starvation. Yet, these two vacuolar trafficking pathways share a number of identical molecular components and are morphologically very similar. For example, one of the hallmarks of both pathways is the formation of double-membrane cytosolic vesicles that sequester cargo before vacuolar delivery. The origin of the vesicle membrane has been controversial and various lines of evidence have implicated essentially all compartments of the endomembrane system. Despite the analogies between the Cvt pathway and autophagy, earlier work has suggested that the origin of the engulfing vesicle membranes is different; the endoplasmic reticulum is proposed to be required only for autophagy. In contrast, in this study we demonstrate that the endoplasmic reticulum and/or Golgi complex, but not endosomal compartments, play an important role for both yeast transport routes. Along these lines, we demonstrate that Berkeley bodies, a structure generated from the Golgi complex in sec7 cells, are immunolabeled with Atg8, a structural component of autophagosomes. Finally, we also show that none of the yeast t-SNAREs are located at the preautophagosomal structure, the presumed site of double-membrane vesicle formation. Based on our results, we propose two models for Cvt vesicle biogenesis.

scholarly journals PtdIns 3-Kinase Orchestrates Autophagosome Formation in Yeast

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Keisuke Obara ◽  
Yoshinori Ohsumi
Keyword(s):  
Membrane Structure ◽  
Protein Complexes ◽  
Eukaryotic Cells ◽  
Autophagosome Formation ◽  
Inner Membrane ◽  
Double Membrane ◽  
Atg Proteins ◽  
Related Proteins ◽  
Lytic Compartment ◽  
Enzymatic Product

Eukaryotic cells can massively transport their own cytoplasmic contents into a lytic compartment, the vacuole/lysosome, for recycling through a conserved system called autophagy. The key process in autophagy is the sequestration of cytoplasmic contents within a double-membrane structure, the autophagosome. Autophagosome formation requires the elaborate cooperation of Atg (autophagy-related) proteins and lipid molecules. Phosphorylation of phosphatidylinositol (PtdIns) by a PtdIns 3-kinase, Vps34, is a key step in coordinating Atg proteins and lipid molecules. Vps34 forms two distinct protein complexes, only one of which is involved in generating autophagic membranes. Upon induction of autophagy, PtdIns(3)P, the enzymatic product of PtdIns 3-kinase, is massively transported into the lumen of the vacuoleviaautophagy. PtdIns(3)Pis enriched on the inner membrane of the autophagosome. PtdIns(3)Precruits the Atg18−Atg2 complex and presumably other Atg proteins to autophagic membranes, thereby coordinating lipid molecules and Atg proteins.

scholarly journals Rab6 Regulates Both ZW10/RINT-1– and Conserved Oligomeric Golgi Complex-dependent Golgi Trafficking and Homeostasis

2007 ◽  
Vol 18 (10) ◽  
pp. 4129-4142 ◽  
Author(s):  
Yi Sun ◽  
Anna Shestakova ◽  
Lauren Hunt ◽  
Siddharth Sehgal ◽  
Vladimir Lupashin ◽  
...  
Keyword(s):  
Protein Complexes ◽  
Mitotic Checkpoint ◽  
Dominant Negative ◽  
Enzyme Recycling ◽  
Cog Complex ◽  
Protein Receptor ◽  
Conserved Oligomeric Golgi Complex ◽  
Conserved Oligomeric Golgi ◽  
Mitotic Checkpoint Protein ◽  
Interfering Rna

We used multiple approaches to investigate the role of Rab6 relative to Zeste White 10 (ZW10), a mitotic checkpoint protein implicated in Golgi/endoplasmic reticulum (ER) trafficking/transport, and conserved oligomeric Golgi (COG) complex, a putative tether in retrograde, intra-Golgi trafficking. ZW10 depletion resulted in a central, disconnected cluster of Golgi elements and inhibition of ERGIC53 and Golgi enzyme recycling to ER. Small interfering RNA (siRNA) against RINT-1, a protein linker between ZW10 and the ER soluble N-ethylmaleimide-sensitive factor attachment protein receptor, syntaxin 18, produced similar Golgi disruption. COG3 depletion fragmented the Golgi and produced vesicles; vesicle formation was unaffected by codepletion of ZW10 along with COG, suggesting ZW10 and COG act separately. Rab6 depletion did not significantly affect Golgi ribbon organization. Epistatic depletion of Rab6 inhibited the Golgi-disruptive effects of ZW10/RINT-1 siRNA or COG inactivation by siRNA or antibodies. Dominant-negative expression of guanosine diphosphate-Rab6 suppressed ZW10 knockdown induced-Golgi disruption. No cross-talk was observed between Rab6 and endosomal Rab5, and Rab6 depletion failed to suppress p115 (anterograde tether) knockdown-induced Golgi disruption. Dominant-negative expression of a C-terminal fragment of Bicaudal D, a linker between Rab6 and dynactin/dynein, suppressed ZW10, but not COG, knockdown-induced Golgi disruption. We conclude that Rab6 regulates distinct Golgi trafficking pathways involving two separate protein complexes: ZW10/RINT-1 and COG.

scholarly journals Septins are involved at the early stages of macroautophagy inS. cerevisiae

2016 ◽  
Author(s):  
Gaurav Barve ◽  
Shreyas Sridhar ◽  
Amol Aher ◽  
Sunaina Singh ◽  
Lakshmeesha K.N. ◽  
...  
Keyword(s):  
Membrane Vesicle ◽  
Degradation Pathway ◽  
Permissive Temperature ◽  
Autophagosome Formation ◽  
Double Membrane ◽  
Early Stages ◽  
Gtp Binding ◽  
Bud Neck ◽  
Ts Mutant

Autophagy is a conserved cellular degradation pathway wherein a double membrane vesicle, called as an autophagosome captures longlived proteins, damaged or superfluous organelles and delivers to the lysosome for degradation1. We have identified a novel role for septins in autophagy. Septins are GTP-binding proteins that localize at the bud-neck and are involved in cytokinesis in budding yeast2. We show that septins under autophagy prevalent conditions are majorly localized to the cytoplasm in the form of punctate structures. Further, we report that septins not only localize to pre-autophagosomal structure (PAS) but also to autophagosomes in the form of punctate structures. Interestingly, septins also form small non-canonical rings around PAS during autophagy. Furthermore, we observed that in one of the septin Ts" mutant,cdc10-5, the anterograde trafficking of Atg9 was affected at the non-permissive temperature (NPT). All these results suggest a role of septins in early stages of autophagy during autophagosome formation.

scholarly journals The Autophagy Machinery in Human-Parasitic Protists; Diverse Functions for Universally Conserved Proteins

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1258
Author(s):  
Hirokazu Sakamoto ◽  
Kumiko Nakada-Tsukui ◽  
Sébastien Besteiro
Keyword(s):  
Membrane Vesicle ◽  
Model Organisms ◽  
Unicellular Eukaryotes ◽  
Current State ◽  
Important Challenge ◽  
Molecular Machinery ◽  
Cellular Machinery ◽  
Apparent Reduction ◽  
Related Proteins ◽  
Genome Projects

Autophagy is a eukaryotic cellular machinery that is able to degrade large intracellular components, including organelles, and plays a pivotal role in cellular homeostasis. Target materials are enclosed by a double membrane vesicle called autophagosome, whose formation is coordinated by autophagy-related proteins (ATGs). Studies of yeast and Metazoa have identified approximately 40 ATGs. Genome projects for unicellular eukaryotes revealed that some ATGs are conserved in all eukaryotic supergroups but others have arisen or were lost during evolution in some specific lineages. In spite of an apparent reduction in the ATG molecular machinery found in parasitic protists, it has become clear that ATGs play an important role in stage differentiation or organelle maintenance, sometimes with an original function that is unrelated to canonical degradative autophagy. In this review, we aim to briefly summarize the current state of knowledge in parasitic protists, in the light of the latest important findings from more canonical model organisms. Determining the roles of ATGs and the diversity of their functions in various lineages is an important challenge for understanding the evolutionary background of autophagy.

scholarly journals Scanning Electron-Assisted Dielectric Microscopy Reveals Autophagosome Formation by LC3 and ATG12 in Cultured Mammalian Cells

2021 ◽  
Vol 22 (4) ◽  
pp. 1834
Author(s):  
Tomoko Okada ◽  
Toshihiko Ogura
Keyword(s):  
Mammalian Cells ◽  
Culture Medium ◽  
Related Gene ◽  
Autophagosome Formation ◽  
Intact Cells ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
The Difference ◽  
Related Proteins ◽  
Scanning Electron

Autophagy is an intracellular self-devouring system that plays a central role in cellular recycling. The formation of functional autophagosomes depends on several autophagy-related proteins, including the microtubule-associated proteins 1A/1B light chain 3 (LC3) and the conserved autophagy-related gene 12 (Atg12). We have recently developed a novel scanning electron-assisted dielectric microscope (SE-ADM) for nanoscale observations of intact cells. Here, we used the SE-ADM system to observe LC3- and Atg12-containing autophagosomes in cells labelled in the culture medium with antibodies conjugated to colloidal gold particles. We observed that, during autophagosome formation, Atg12 localized along the actin meshwork structure, whereas LC3 formed arcuate or circular alignments. Our system also showed a difference in the distribution of LC3 and Atg12; Atg12 was broadly distributed while LC3 was more localized. The difference in the spatial distribution demonstrated by our system explains the difference in the size of fluorescent spots due to the fluorescently labelled antibodies observed using optical microscopy. The direct SE-ADM observation of cells should thus be effective in analyses of autophagosome formation.

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