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 Atg27 Is Required for Autophagy-dependent Cycling of Atg9

2007 ◽  
Vol 18 (2) ◽  
pp. 581-593 ◽  
Author(s):  
Wei-Lien Yen ◽  
Julie E. Legakis ◽  
Usha Nair ◽  
Daniel J. Klionsky
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Golgi Complex ◽  
Transmembrane Protein ◽  
Eukaryotic Cells ◽  
Vesicle Formation ◽  
Catabolic Pathway ◽  
Autophagosome Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Double Membrane ◽  
Selective Autophagy

Autophagy is a catabolic pathway for the degradation of cytosolic proteins or organelles and is conserved among all eukaryotic cells. The hallmark of autophagy is the formation of double-membrane cytosolic vesicles, termed autophagosomes, which sequester cytoplasm; however, the mechanism of vesicle formation and the membrane source remain unclear. In the yeast Saccharomyces cerevisiae, selective autophagy mediates the delivery of specific cargos to the vacuole, the analog of the mammalian lysosome. The transmembrane protein Atg9 cycles between the mitochondria and the pre-autophagosomal structure, which is the site of autophagosome biogenesis. Atg9 is thought to mediate the delivery of membrane to the forming autophagosome. Here, we characterize a second transmembrane protein Atg27 that is required for specific autophagy in yeast. Atg27 is required for Atg9 cycling and shuttles between the pre-autophagosomal structure, mitochondria, and the Golgi complex. These data support a hypothesis that multiple membrane sources supply the lipids needed for autophagosome formation.

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 Innenarchitektur der Zellkraftwerke — Membranfalten in Hochauflösung

BIOspektrum ◽  
2021 ◽  
Vol 27 (2) ◽  
pp. 161-164
Author(s):  
Till Stephan ◽  
Peter Ilgen ◽  
Stefan Jakobs
Keyword(s):  
Electron Microscopy ◽  
Protein Complex ◽  
Mitochondrial Protein ◽  
Light And Electron Microscopy ◽  
Super Resolution ◽  
Eukaryotic Cells ◽  
Inner Membrane ◽  
Double Membrane ◽  
Cellular Organelles

AbstractMitochondria are essential cellular organelles, which supply eukaryotic cells with the universal energy carrier adenosine triphosphate. These organelles feature a unique double-membrane architecture, which is formed by a smooth outer membrane and a highly folded inner membrane. Harnessing super-resolution light and electron microscopy, we investigate the role of MICOS, a large mitochondrial protein complex, in determining the complex folding of the inner membrane.

scholarly journals Atg9 vesicles are an important membrane source during early steps of autophagosome formation

2012 ◽  
Vol 198 (2) ◽  
pp. 219-233 ◽  
Author(s):  
Hayashi Yamamoto ◽  
Soichiro Kakuta ◽  
Tomonobu M. Watanabe ◽  
Akira Kitamura ◽  
Takayuki Sekito ◽  
...  
Keyword(s):  
Golgi Apparatus ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Membrane Structures ◽  
Autophagosome Formation ◽  
Early Step ◽  
Double Membrane ◽  
Lytic Compartment ◽  
Insight Into

During the process of autophagy, cytoplasmic materials are sequestered by double-membrane structures, the autophagosomes, and then transported to a lytic compartment to be degraded. One of the most fundamental questions about autophagy involves the origin of the autophagosomal membranes. In this study, we focus on the intracellular dynamics of Atg9, a multispanning membrane protein essential for autophagosome formation in yeast. We found that the vast majority of Atg9 existed on cytoplasmic mobile vesicles (designated Atg9 vesicles) that were derived from the Golgi apparatus in a process involving Atg23 and Atg27. We also found that only a few Atg9 vesicles were required for a single round of autophagosome formation. During starvation, several Atg9 vesicles assembled individually into the preautophagosomal structure, and eventually, they are incorporated into the autophagosomal outer membrane. Our findings provide conclusive linkage between the cytoplasmic Atg9 vesicles and autophagosomal membranes and offer new insight into the requirement for Atg9 vesicles at the early step of autophagosome formation.

The ultrastructure of the double membrane-bound bodies and endoplasmic reticulum in serial sections of wheat spot mosaic-affected wheat plants

1990 ◽  
Vol 48 (3) ◽  
pp. 694-695
Author(s):  
M. H. Chen ◽  
C. Hiruki
Keyword(s):  
Endoplasmic Reticulum ◽  
High Resolution ◽  
Membrane Structure ◽  
Mosaic Disease ◽  
Serial Sections ◽  
Thin Sections ◽  
Double Membrane ◽  
Southern Alberta ◽  
Membrane Bound ◽  
Scanning Em

Wheat spot mosaic disease was first discovered in southern Alberta, Canada, in 1956. A hitherto unidentified disease-causing agent, transmitted by the eriophyid mite, caused chlorosis, stunting and finally severe necrosis resulting in the death of the affected plants. Double membrane-bound bodies (DMBB), 0.1-0.2 μm in diameter were found to be associated with the disease.Young tissues of leaf and root from 4-wk-old infected wheat plants were fixed, dehydrated, and embedded in Spurr’s resin. Serial sections were collected on slot copper grids and stained. The thin sections were then examined with a Hitachi H-7000 TEM at 75 kV. The membrane structure of the DMBBs was studied by numbering them individually and tracing along the sections to see any physical connection with endoplasmic reticulum (ER) membranes. For high resolution scanning EM, a modification of Tanaka’s method was used. The specimens were examined with a Hitachi Model S-570 SEM in its high resolution mode at 20 kV.

scholarly journals Structural catalog of core Atg proteins opens new era of autophagy research

2021 ◽  
Author(s):  
Kazuaki Matoba ◽  
Nobuo N Noda
Keyword(s):  
De Novo ◽  
Structural Information ◽  
Membrane Dynamics ◽  
Autophagosome Formation ◽  
New Era ◽  
Intracellular Degradation ◽  
Atg Proteins ◽  
Biological Studies ◽  
Evolutionarily Conserved ◽  
Biological Methods

Summary Autophagy, which is an evolutionarily conserved intracellular degradation system, involves de novo generation of autophagosomes that sequester and deliver diverse cytoplasmic materials to the lysosome for degradation. Autophagosome formation is mediated by approximately 20 core autophagy-related (Atg) proteins, which collaborate to mediate complicated membrane dynamics during autophagy. To elucidate the molecular functions of these Atg proteins in autophagosome formation, many researchers have tried to determine the structures of Atg proteins by using various structural biological methods. Although not sufficient, the basic structural catalog of all core Atg proteins was established. In this review article, we summarize structural biological studies of core Atg proteins, with an emphasis on recently unveiled structures, and describe the mechanistic breakthroughs in autophagy research that have derived from new structural information.

scholarly journals Mitochondrial Protein Network: From Biogenesis to Bioenergetics in Health and Disease

2020 ◽  
Vol 22 (1) ◽  
pp. 1
Author(s):  
Alessandra Ferramosca
Keyword(s):  
Crucial Role ◽  
Mitochondrial Protein ◽  
Protein Network ◽  
Eukaryotic Cells ◽  
Double Membrane ◽  
Health And Disease ◽  
Membrane Bound

Mitochondria are double membrane-bound organelles which are essential for the viability of eukaryotic cells, because they play a crucial role in bioenergetics, metabolism and signaling [...]

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.

scholarly journals Interaction of the Aspergillus nidulans Microtubule-Organizing Center (MTOC) Component ApsB with Gamma-Tubulin and Evidence for a Role of a Subclass of Peroxisomes in the Formation of Septal MTOCs

2010 ◽  
Vol 9 (5) ◽  
pp. 795-805 ◽  
Author(s):  
Nadine Zekert ◽  
Daniel Veith ◽  
Reinhard Fischer
Keyword(s):  
Aspergillus Nidulans ◽  
Protein Complexes ◽  
Spindle Pole ◽  
Eukaryotic Cells ◽  
Microtubule Organizing Center ◽  
Body Protein ◽  
Content Type ◽  
C Terminus ◽  
Peroxisomal Targeting ◽  
Gamma Tubulin

ABSTRACT Peroxisomes are a diverse class of organelles involved in different physiological processes in eukaryotic cells. Although proteins imported into peroxisomes carry a peroxisomal targeting sequence at the C terminus (PTS1) or an alternative one close to the N terminus (PTS2), the protein content of peroxisomes varies drastically. Here we suggest a new class of peroxisomes involved in microtubule (MT) formation. Eukaryotic cells assemble MTs from distinct points in the cell. In the fungus Aspergillus nidulans, septum-associated microtubule-organizing centers (sMTOCs) are very active in addition to the spindle pole bodies (SPBs). Previously, we identified a novel MTOC-associated protein, ApsB (Schizosaccharomyces pombe mto1), whose absence affected MT formation from sMTOCs more than from SPBs, suggesting that the two protein complexes are organized differently. We show here that sMTOCs share at least two further components, gamma-tubulin and GcpC (S. pombe Alp6) with SPBs and found that ApsB interacts with gamma-tubulin. In addition, we discovered that ApsB interacts with the Woronin body protein HexA and is targeted to a subclass of peroxisomes via a PTS2 peroxisomal targeting sequence. The PTS2 motif was necessary for function but could be replaced with a PTS1 motif at the C terminus of ApsB. These results suggest a novel function for a subclass of peroxisomes in cytoskeletal organization.

scholarly journals Fine-tuning autophagy: from transcriptional to posttranslational regulation

2016 ◽  
Vol 311 (3) ◽  
pp. C351-C362 ◽  
Author(s):  
Joëlle Botti-Millet ◽  
Anna Chiara Nascimbeni ◽  
Nicolas Dupont ◽  
Etienne Morel ◽  
Patrice Codogno
Keyword(s):  
Posttranslational Modifications ◽  
Inflammatory Responses ◽  
Chronic Inflammatory Disease ◽  
Autophagic Vacuole ◽  
Tissue Homeostasis ◽  
Fine Tuning ◽  
Eukaryotic Cells ◽  
Posttranslational Regulation ◽  
Atg Proteins ◽  
Diabetes And Obesity

Macroautophagy (hereafter called autophagy) is a vacuolar lysosomal pathway for degradation of intracellular material in eukaryotic cells. Autophagy plays crucial roles in tissue homeostasis, in adaptation to stress situations, and in immune and inflammatory responses. Alteration of autophagy is associated with cancer, diabetes and obesity, cardiovascular disease, neurodegenerative disease, autoimmune disease, infection, and chronic inflammatory disease. Autophagy is controlled by autophagy-related (ATG) proteins that act in a coordinated manner to build up the initial autophagic vacuole named the autophagosome. It is now known that the activities of ATG proteins are modulated by posttranslational modifications such as phosphorylation, ubiquitination, and acetylation. Moreover, transcriptional and epigenetic controls are involved in the regulation of autophagy in stress situations. Here we summarize and discuss how posttranslational modifications and transcriptional and epigenetic controls regulate the involvement of autophagy in the proteostasis network.

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