scholarly journals ER-phagy requires Lnp1, a protein that stabilizes rearrangements of the ER network

2018 ◽  
Vol 115 (27) ◽  
pp. E6237-E6244 ◽  
Author(s):  
Shuliang Chen ◽  
Yixian Cui ◽  
Smriti Parashar ◽  
Peter J. Novick ◽  
Susan Ferro-Novick
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Scaffold Protein ◽  
Cell Cortex ◽  
Wild Type ◽  
Autophagosome Formation ◽  
Cell Interior ◽  
Rapamycin Treatment ◽  
Selective Autophagy ◽  
Latrunculin A

The endoplasmic reticulum (ER) forms a contiguous network of tubules and sheets that is predominantly associated with the cell cortex in yeast. Upon treatment with rapamycin, the ER undergoes degradation by selective autophagy. This process, termed ER-phagy, requires Atg40, a selective autophagy receptor that localizes to the cortical ER. Here we report that ER-phagy also requires Lnp1, an ER membrane protein that normally resides at the three-way junctions of the ER network, where it serves to stabilize the network as it is continually remodeled. Rapamycin treatment increases the expression of Atg40, driving ER domains marked by Atg40 puncta to associate with Atg11, a scaffold protein needed to form autophagosomes. Although Atg40 largely localizes to the cortical ER, the autophagy machinery resides in the cell interior. The localization of Atg40 to sites of autophagosome formation is blocked in an lnp1Δ mutant or upon treatment of wild-type cells with the actin-depolymerizing drug Latrunculin A. This prevents the association of Atg40 with Atg11 and the packaging of the ER into autophagosomes. We propose that Lnp1 is needed to stabilize the actin-dependent remodeling of the ER that is essential for ER-phagy.

scholarly journals Autophagosome formation in relation to the endoplasmic reticulum

2020 ◽  
Vol 27 (1) ◽  
Author(s):  
Yo-hei Yamamoto ◽  
Takeshi Noda
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
De Novo ◽  
Transmembrane Protein ◽  
Lipid Transfer ◽  
Membrane Structures ◽  
Autophagosome Formation ◽  
Selective Autophagy ◽  
The Relationship ◽  
Er Membrane

Abstract Autophagy is a process in which a myriad membrane structures called autophagosomes are formed de novo in a single cell, which deliver the engulfed substrates into lysosomes for degradation. The size of the autophagosomes is relatively uniform in non-selective autophagy and variable in selective autophagy. It has been recently established that autophagosome formation occurs near the endoplasmic reticulum (ER). In this review, we have discussed recent advances in the relationship between autophagosome formation and endoplasmic reticulum. Autophagosome formation occurs near the ER subdomain enriched with phospholipid synthesizing enzymes like phosphatidylinositol synthase (PIS)/CDP-diacylglycerol-inositol 3-phosphatidyltransferase (CDIPT) and choline/ethanolamine phosphotransferase 1 (CEPT1). Autophagy-related protein 2 (Atg2), which is involved in autophagosome formation has a lipid transfer capacity and is proposed to directly transfer the lipid molecules from the ER to form autophagosomes. Vacuole membrane protein 1 (VMP1) and transmembrane protein 41b (TMEM41b) are ER membrane proteins that are associated with the formation of the subdomain. Recently, we have reported that an uncharacterized ER membrane protein possessing the DNAJ domain, called ERdj8/DNAJC16, is associated with the regulation of the size of autophagosomes. The localization of ERdj8/DNAJC16 partially overlaps with the PIS-enriched ER subdomain, thereby implying its association with autophagosome size determination.

scholarly journals Spatial control of avidity regulates initiation and progression of selective autophagy

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David M. Hollenstein ◽  
Mariya Licheva ◽  
Nicole Konradi ◽  
David Schweida ◽  
Hector Mancilla ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Membrane ◽  
Vacuolar Membrane ◽  
Phosphatidylinositol 3 Kinase ◽  
Autophagosome Formation ◽  
Spatial Control ◽  
Selective Autophagy ◽  
Phagophore Assembly Site ◽  
Assembly Site ◽  
Phosphatidylinositol 3

AbstractAutophagosomes form at the endoplasmic reticulum in mammals, and between the vacuole and the endoplasmic reticulum in yeast. However, the roles of these sites and the mechanisms regulating autophagosome formation are incompletely understood. Vac8 is required for autophagy and recruits the Atg1 kinase complex to the vacuole. Here we show that Vac8 acts as a central hub to nucleate the phagophore assembly site at the vacuolar membrane during selective autophagy. Vac8 directly recruits the cargo complex via the Atg11 scaffold. In addition, Vac8 recruits the phosphatidylinositol 3-kinase complex independently of autophagy. Cargo-dependent clustering and Vac8-dependent sequestering of these early autophagy factors, along with local Atg1 activation, promote phagophore assembly site assembly at the vacuole. Importantly, ectopic Vac8 redirects autophagosome formation to the nuclear membrane, indicating that the vacuolar membrane is not specifically required. We propose that multiple avidity-driven interactions drive the initiation and progression of selective autophagy.

scholarly journals Endoplasmic Reticulum–Mitochondria Contacts Are Required for Pexophagy in Saccharomyces cerevisiae

Contact ◽  
2019 ◽  
Vol 2 ◽  
pp. 251525641882158 ◽  
Author(s):  
Xu Liu ◽  
Xin Wen ◽  
Daniel J. Klionsky
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Lipid Metabolism ◽  
Membrane Protein ◽  
Mutant Form ◽  
Peroxisomal Membrane ◽  
Cellular Homeostasis ◽  
Selective Autophagy ◽  
Contact Sites ◽  
Autophagic Degradation

Peroxisomes play important roles in lipid metabolism. Surplus or damaged peroxisomes can be selectively targeted for autophagic degradation, a process termed pexophagy. Maintaining a proper level of pexophagy is critical for cellular homeostasis. Here, we found that endoplasmic reticulum (ER)–mitochondria contact sites are necessary for efficient pexophagy. During pexophagy, the peroxisomes destined for degradation are adjacent to the ER–mitochondria encounter structure (ERMES) that mediates the formation of ER–mitochondria contacts; disruption of the ERMES results in a severe defect in pexophagy. We show that a mutant form of Mdm34, a component of the ERMES, which impairs ERMES formation and diminishes its association with the peroxisomal membrane protein Pex11, also causes defects in pexophagy. The dynamin-related GTPase Vps1, which is specific for peroxisomal fission, is recruited to the peroxisomes at ER–mitochondria contacts by the selective autophagy scaffold Atg11 and the pexophagy receptor Atg36, facilitating peroxisome degradation.

scholarly journals Membrane Delivery to the Yeast Autophagosome from the Golgi–Endosomal System

2010 ◽  
Vol 21 (22) ◽  
pp. 3998-4008 ◽  
Author(s):  
Yohei Ohashi ◽  
Sean Munro
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Autophagosome Formation ◽  
Endosomal System

While many of the proteins required for autophagy have been identified, the source of the membrane of the autophagosome is still unresolved with the endoplasmic reticulum (ER), endosomes, and mitochondria all having been evoked. The integral membrane protein Atg9 is delivered to the autophagosome during starvation and in the related cytoplasm-to-vacuole (Cvt) pathway that occurs constitutively in yeast. We have examined the requirements for delivery of Atg9-containing membrane to the yeast autophagosome. Atg9 does not appear to originate from mitochondria, and Atg9 cannot reach the forming autophagosome directly from the ER or early Golgi. Components of traffic between Golgi and endosomes are known to be required for the Cvt pathway but do not appear required for autophagy in starved cells. However, we find that pairwise combinations of mutations in Golgi-endosomal traffic components apparently only required for the Cvt pathway can cause profound defects in Atg9 delivery and autophagy in starved cells. Thus it appears that membrane that contains Atg9 is delivered to the autophagosome from the Golgi-endosomal system rather than from the ER or mitochondria. This is underestimated by examination of single mutants, providing a possible explanation for discrepancies between yeast and mammalian studies on Atg9 localization and autophagosome formation.

Correction of delF508-CFTR activity with benzo(c)quinolizinium compounds through facilitation of its processing in cystic fibrosis airway cells

2001 ◽  
Vol 114 (22) ◽  
pp. 4073-4081
Author(s):  
Robert L. Dormer ◽  
Renaud Dérand ◽  
Ceinwen M. McNeilly ◽  
Yvette Mettey ◽  
Laurence Bulteau-Pignoux ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Protein Trafficking ◽  
Apical Region ◽  
Major Advance ◽  
Wild Type ◽  
Cl Transport ◽  
Airway Cells

A number of genetic diseases, including cystic fibrosis, have been identified as disorders of protein trafficking associated with retention of mutant protein within the endoplasmic reticulum. In the presence of the benzo(c)quinolizinium drugs, MPB-07 and its congener MPB-91, we show the activation of cystic fibrosis transmembrane conductance regulator (CFTR) delF508 channels in IB3-1 human cells, which express endogenous levels of delF508-CFTR. These drugs were without effect on the Ca2+-activated Cl– transport, whereas the swelling-activated Cl– transport was found altered in MPB-treated cells. Immunoprecipitation and in vitro phosphorylation shows a 20% increase of the band C form of delF508 after MPB treatment. We then investigated the effect of these drugs on the extent of mislocalisation of delF508-CFTR in native airway cells from cystic fibrosis patients. We first showed that delF508 CFTR was characteristically restricted to an endoplasmic reticulum location in approximately 80% of untreated cells from CF patients homozygous for the delF508-CFTR mutation. By contrast, 60-70% of cells from non-CF patients showed wild-type CFTR in an apical location. MPB-07 treatment caused dramatic relocation of delF508-CFTR to the apical region such that the majority of delF508/delF508 CF cells showed a similar CFTR location to that of wild-type. MPB-07 had no apparent effect on the distribution of wild-type CFTR, the apical membrane protein CD59 or the ER membrane Ca2+,Mg-ATPase. We also showed a similar pharmacological effect in nasal cells freshly isolated from a delF508/G551D CF patient. The results demonstrate selective redirection of a mutant membrane protein using cell-permeant small molecules of the benzo(c)quinolizinium family and provide a major advance towards development of a targetted drug treatment for cystic fibrosis and other disorders of protein trafficking.

scholarly journals Sarcolipin alters SERCA1a interdomain communication by impairing binding of both calcium and ATP

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cédric Montigny ◽  
Dong Liang Huang ◽  
Veronica Beswick ◽  
Thomas Barbot ◽  
Christine Jaxel ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Functional Role ◽  
Published Data ◽  
Allosteric Effect ◽  
Transport Activity ◽  
Wild Type ◽  
Experimental Conditions ◽  
Interdomain Communication

AbstractSarcolipin (SLN), a single-spanning membrane protein, is a regulator of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA1a). Chemically synthesized SLN, palmitoylated or not (pSLN or SLN), and recombinant wild-type rabbit SERCA1a expressed in S. cerevisiae design experimental conditions that provide a deeper understanding of the functional role of SLN on the regulation of SERCA1a. Our data show that chemically synthesized SLN interacts with recombinant SERCA1a, with calcium-deprived E2 state as well as with calcium-bound E1 state. This interaction hampers the binding of calcium in agreement with published data. Unexpectedly, SLN has also an allosteric effect on SERCA1a transport activity by impairing the binding of ATP. Our results reveal that SLN significantly slows down the E2 to Ca2.E1 transition of SERCA1a while it affects neither phosphorylation nor dephosphorylation. Comparison with chemically synthesized SLN deprived of acylation demonstrates that palmitoylation is not necessary for either inhibition or association with SERCA1a. However, it has a small but statistically significant effect on SERCA1a phosphorylation when various ratios of SLN-SERCA1a or pSLN-SERCA1a are tested.

TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum

2019 ◽  
Vol 476 (21) ◽  
pp. 3241-3260
Author(s):  
Sindhu Wisesa ◽  
Yasunori Yamamoto ◽  
Toshiaki Sakisaka
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Mammalian Cells ◽  
Coiled Coil ◽  
Transmembrane Domains ◽  
Domain Family ◽  
Coiled Coil Domain ◽  
U2os Cells ◽  
Er Membrane

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

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