scholarly journals The multifaceted functions of ATG16L1 in autophagy and related processes

2020 ◽  
Vol 133 (20) ◽  
pp. jcs249227
Author(s):  
Noor Gammoh
Keyword(s):  
De Novo ◽  
Membrane Vesicles ◽  
Vesicular Trafficking ◽  
Enzymatic Activities ◽  
Lysosomal Hydrolases ◽  
Related Proteins

ABSTRACTAutophagy requires the formation of membrane vesicles, known as autophagosomes, that engulf cellular cargoes and subsequently recruit lysosomal hydrolases for the degradation of their contents. A number of autophagy-related proteins act to mediate the de novo biogenesis of autophagosomes and vesicular trafficking events that are required for autophagy. Of these proteins, ATG16L1 is a key player that has important functions at various stages of autophagy. Numerous recent studies have begun to unravel novel activities of ATG16L1, including interactions with proteins and lipids, and how these mediate its role during autophagy and autophagy-related processes. Various domains have been identified within ATG16L1 that mediate its functions in recognising single and double membranes and activating subsequent autophagy-related enzymatic activities required for the recruitment of lysosomes. These recent findings, as well as the historical discovery of ATG16L1, pathological relevance, unresolved questions and contradictory observations, will be discussed here.

scholarly journals A reversible autophagy inhibitor blocks autophagosome–lysosome fusion by preventing Stx17 loading onto autophagosomes

2019 ◽  
Vol 30 (17) ◽  
pp. 2283-2295 ◽  
Author(s):  
Somya Vats ◽  
Ravi Manjithaya
Keyword(s):  
Egf Receptor ◽  
De Novo ◽  
Degradation Pathway ◽  
Vesicular Trafficking ◽  
Autophagic Flux ◽  
Lysosomal Degradation ◽  
Evolutionarily Conserved ◽  
Multistep Process ◽  
Novel Method ◽  
Related Proteins

Autophagy is an evolutionarily conserved intracellular lysosomal degradation pathway. It is a multistep process involving de novo formation of double membrane autophagosomes that capture cytosolic constituents (cargo) and eventually fuse with lysosomes wherein the cargo gets degraded and resulting simpler biomolecules get recycled. In addition to their autophagy function, several of the autophagy-related proteins work at the interface of other vesicular trafficking pathways. Hence, development of specific autophagy modulators that do not perturb general endo-lysosomal traffic possesses unique challenges. In this article, we report a novel small molecule EACC that inhibits autophagic flux by blocking autophagosome–lysosome fusion. Strikingly, unlike other late stage inhibitors, EACC does not have any effect on lysosomal properties or on endocytosis-mediated degradation of EGF receptor. EACC affects the translocation of SNAREs Stx17 and SNAP29 on autophagosomes without impeding the completion of autophagosomes. EACC treatment also reduces the interaction of Stx17 with the HOPS subunit VPS33A and the cognate lysosomal R-SNARE VAMP8. Interestingly, this effect of EACC although quite robust is reversible and hence EACC can be used as a tool to study autophagosomal SNARE trafficking. Our results put forward a novel method to block autophagic flux by impeding the action of the autophagosomal SNAREs.

scholarly journals Retromer has a selective function in cargo sorting via endosome transport carriers

2018 ◽  
Vol 218 (2) ◽  
pp. 615-631 ◽  
Author(s):  
Yi Cui ◽  
Julian M. Carosi ◽  
Zhe Yang ◽  
Nicholas Ariotti ◽  
Markus C. Kerr ◽  
...  
Keyword(s):  
Vesicular Trafficking ◽  
Lysosomal Hydrolases ◽  
Cell Level ◽  
Ultrastructural Alteration ◽  
Membrane Protein Complex ◽  
Lysosomal Function ◽  
Trafficking Pathway ◽  
Peripheral Membrane Protein ◽  
And Function ◽  
Proteolytic Capacity

Retromer is a peripheral membrane protein complex that coordinates multiple vesicular trafficking events within the endolysosomal system. Here, we demonstrate that retromer is required for the maintenance of normal lysosomal morphology and function. The knockout of retromer subunit Vps35 causes an ultrastructural alteration in lysosomal structure and aberrant lysosome function, leading to impaired autophagy. At the whole-cell level, knockout of retromer Vps35 subunit reduces lysosomal proteolytic capacity as a consequence of the improper processing of lysosomal hydrolases, which is dependent on the trafficking of the cation-independent mannose 6-phosphate receptor (CI-M6PR). Incorporation of CI-M6PR into endosome transport carriers via a retromer-dependent process is restricted to those tethered by GCC88 but not golgin-97 or golgin-245. Finally, we show that this retromer-dependent retrograde cargo trafficking pathway requires SNX3, but not other retromer-associated cargo binding proteins, such as SNX27 or SNX-BAR proteins. Therefore, retromer does contribute to the retrograde trafficking of CI-M6PR required for maturation of lysosomal hydrolases and lysosomal function.

Growth-dependent regulation of system A in SV40-transformed fetal rat hepatocytes

1988 ◽  
Vol 255 (3) ◽  
pp. C261-C270 ◽  
Author(s):  
M. E. Handlogten ◽  
M. S. Kilberg
Keyword(s):  
Cell Density ◽  
De Novo ◽  
Membrane Vesicles ◽  
Rat Hepatocytes ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Plasma Membrane Vesicles ◽  
Intact Cells ◽  
System A

Fetal RLA209-15 hepatocytes, transformed with a temperature-sensitive SV40 mutant, behave like fully differentiated cells at the growth-restrictive temperature of 40 degrees C. Conversely, incubation at the growth-permissive temperature of 33 degrees C results in a transformed phenotype characterized by rapid cell division and decreased production of liver-specific proteins. The results presented here demonstrate that the cells at 33 degrees C exhibited high rates of system A transport, but transfer to 40 degrees C reduced the activity greater than 50% within 24 h. This decline in transport was independent of cell density, although the basal rate of uptake was inversely proportional to cell density in rapidly dividing cells. Transfer of cells from 40 to 33 degrees C resulted in an enhancement of system A activity that was blocked by tunicamycin. Plasma membrane vesicles from cells maintained at either 33 or 40 degrees C retained uptake rates proportional to those in the intact cells; this difference in transport activity could also be demonstrated after detergent solubilization and reconstitution. Collectively, these data indicate that de novo synthesis of the system A carrier is regulated in conjunction with temperature-dependent cell growth in RLA209-15 hepatocytes.

scholarly journals SPO71 Encodes a Developmental Stage-Specific Partner for Vps13 in Saccharomyces cerevisiae

2013 ◽  
Vol 12 (11) ◽  
pp. 1530-1537 ◽  
Author(s):  
Jae-Sook Park ◽  
Yuuya Okumura ◽  
Hiroyuki Tachikawa ◽  
Aaron M. Neiman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
De Novo ◽  
Ectopic Expression ◽  
Membrane Vesicles ◽  
Specific Gene ◽  
Wild Type ◽  
Protein Mutation ◽  
Prospore Membrane ◽  
In The Wild ◽  
Membrane Morphogenesis

ABSTRACT The creation of haploid gametes in yeast, termed spores, requires the de novo formation of membranes within the cytoplasm. These membranes, called prospore membranes, enclose the daughter nuclei generated by meiosis. Proper growth and closure of prospore membranes require the highly conserved Vps13 protein. Mutation of SPO71 , a meiosis-specific gene first identified as defective in spore formation, was found to display defects in membrane morphogenesis very similar to those seen in vps13 Δ cells. Specifically, prospore membranes are smaller than in the wild type, they fail to close, and membrane vesicles are present within the prospore membrane lumen. As in vps13 Δ cells, the levels of phophatidylinositol-4-phosphate are reduced in the prospore membranes of spo71 Δ cells. SPO71 is required for the translocation of Vps13 from the endosome to the prospore membrane, and ectopic expression of SPO71 in vegetative cells results in mislocalization of Vps13. Finally, the two proteins can be coprecipitated from sporulating cells. We propose that Spo71 is a sporulation-specific partner for Vps13 and that they act in concert to regulate prospore membrane morphogenesis.

scholarly journals Key Regulators of Autophagosome Closure

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2814
Author(s):  
Wenyan Jiang ◽  
Xuechai Chen ◽  
Cuicui Ji ◽  
Wenting Zhang ◽  
Jianing Song ◽  
...  
Keyword(s):  
Recent Progress ◽  
Membrane Vesicles ◽  
Rab Gtpase ◽  
The Core ◽  
Escrt Machinery ◽  
Atg Proteins ◽  
Evolutionarily Conserved ◽  
Atg Genes ◽  
Related Proteins ◽  
Key Questions

Autophagy is an evolutionarily conserved pathway, in which cytoplasmic components are sequestered within double-membrane vesicles called autophagosomes and then transported into lysosomes or vacuoles for degradation. Over 40 conserved autophagy-related (ATG) genes define the core machinery for the five processes of autophagy: initiation, nucleation, elongation, closure, and fusion. In this review, we focus on one of the least well-characterized events in autophagy, namely the closure of the isolation membrane/phagophore to form the sealed autophagosome. This process is tightly regulated by ESCRT machinery, ATG proteins, Rab GTPase and Rab-related proteins, SNAREs, sphingomyelin, and calcium. We summarize recent progress in the regulation of autophagosome closure and discuss the key questions remaining to be addressed.

scholarly journals Specificities of modeling membrane proteins using multi-template homology modeling

2020 ◽  
Author(s):  
Julia Koehler Leman ◽  
Richard Bonneau
Keyword(s):  
Membrane Proteins ◽  
Homology Modeling ◽  
De Novo ◽  
Sequence Similarity ◽  
Query Sequence ◽  
Scoring Function ◽  
Single Model ◽  
Software Suite ◽  
Structural Template ◽  
Related Proteins

AbstractStructures of membrane proteins are challenging to determine experimentally and currently represent only about 2% of the structures in the ProteinDataBank. Because of this disparity, methods for modeling membrane proteins are fewer and of lower quality than those for modeling soluble proteins. However, better expression, crystallization, and cryo-EM techniques have prompted a recent increase in experimental structures of membrane proteins, which can act as templates to predict the structure of closely related proteins through homology modeling. Because homology modeling relies on a structural template, it is easier and more accurate than fold recognition methods or de novo modeling, which are used when the sequence similarity between the query sequence and the sequence of related proteins in structural databases is below 25%. In homology modeling, a query sequence is mapped onto the coordinates of a single template and refined. With the increase in available templates, several templates often cover overlapping segments of the query sequence. Multi-template modeling can be used to identify the best template for local segments and join them into a single model. Here we provide a protocol for modeling membrane proteins from multiple templates in the Rosetta software suite. This approach takes advantage of several integrated frameworks, namely RosettaScripts, RosettaCM, and RosettaMP with the membrane scoring function.

scholarly journals The autophagic membrane tether ATG2A transfers lipids between membranes

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Shintaro Maeda ◽  
Chinatsu Otomo ◽  
Takanori Otomo
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Lipid Transfer Protein ◽  
Membrane Vesicles ◽  
Building Blocks ◽  
Underlying Mechanism ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Membrane Compartment ◽  
Membrane Tether

An enigmatic step in de novo formation of the autophagosome membrane compartment is the expansion of the precursor membrane phagophore, which requires the acquisition of lipids to serve as building blocks. Autophagy-related 2 (ATG2), the rod-shaped protein that tethers phosphatidylinositol 3-phosphate (PI3P)-enriched phagophores to the endoplasmic reticulum (ER), is suggested to be essential for phagophore expansion, but the underlying mechanism remains unclear. Here, we demonstrate that human ATG2A is a lipid transfer protein. ATG2A can extract lipids from membrane vesicles and unload them to other vesicles. Lipid transfer by ATG2A is more efficient between tethered vesicles than between untethered vesicles. The PI3P effectors WIPI4 and WIPI1 associate ATG2A stably to PI3P-containing vesicles, thereby facilitating ATG2A-mediated tethering and lipid transfer between PI3P-containing vesicles and PI3P-free vesicles. Based on these results, we propose that ATG2-mediated transfer of lipids from the ER to the phagophore enables phagophore expansion.

scholarly journals The autophagic membrane tether ATG2A transfers lipids between membranes

2019 ◽  
Author(s):  
Shintaro Maeda ◽  
Chinatsu Otomo ◽  
Takanori Otomo
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Membrane Vesicles ◽  
Building Blocks ◽  
Underlying Mechanism ◽  
Lipid Transfer ◽  
Membrane Compartment ◽  
Membrane Tether ◽  
Phosphatidylinositol 3

AbstractAn enigmatic step in de novo formation of the autophagosome membrane compartment is the expansion of the precursor membrane phagophore, which requires the acquisition of lipids to serve as building blocks. Autophagy-related 2 (ATG2), the rod-shaped protein that tethers phosphatidylinositol 3-phosphate (PI3P)-enriched phagophores to the endoplasmic reticulum (ER), is suggested to be essential for phagophore expansion, but the underlying mechanism remains unclear. Here, we demonstrate that human ATG2A is a lipid-transferring protein. ATG2A can extract lipids from membrane vesicles and unload them to other vesicles. Lipid transfer by ATG2A is more efficient between its tethered vesicles than between untethered vesicles. The PI3P effectors WIPI4 and WIPI1 associate ATG2A stably to PI3P-containing vesicles, thereby facilitating ATG2A-mediated tethering and lipid transfer between PI3P-containing vesicles and PI3P-free vesicles. Based on these results, we propose that ATG2-mediated transfer of lipids from the ER to the phagophore enables phagophore expansion.

Sign in / Sign up

Export Citation Format

Share Document