scholarly journals Rab32 uses its effector reticulon 3L to trigger autophagic degradation of mitochondria-associated membrane (MAM) proteins

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Maria Sol Herrera-Cruz ◽  
Megan C. Yap ◽  
Nasser Tahbaz ◽  
Keelie Phillips ◽  
Laurel Thomas ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Transmembrane Protein ◽  
Membrane Dynamics ◽  
Small Gtpase ◽  
Dependent Manner ◽  
Related Protein ◽  
Intracellular Membrane ◽  
Selective Autophagy ◽  
Large Panel ◽  
Autophagic Degradation

Abstract Background Rab32 is a small GTPase associated with multiple organelles but is particularly enriched at the endoplasmic reticulum (ER). Here, it controls targeting to mitochondria-ER contacts (MERCs), thus influencing composition of the mitochondria-associated membrane (MAM). Moreover, Rab32 regulates mitochondrial membrane dynamics via its effector dynamin-related protein 1 (Drp1). Rab32 has also been reported to induce autophagy, an essential pathway targeting intracellular components for their degradation. However, no autophagy-specific effectors have been identified for Rab32. Similarly, the identity of the intracellular membrane targeted by this small GTPase and the type of autophagy it induces are not known yet. Results To investigate the target of autophagic degradation mediated by Rab32, we tested a large panel of organellar proteins. We found that a subset of MERC proteins, including the thioredoxin-related transmembrane protein TMX1, are specifically targeted for degradation in a Rab32-dependent manner. We also identified the long isoform of reticulon-3 (RTN3L), a known ER-phagy receptor, as a Rab32 effector. Conclusions Rab32 promotes degradation of mitochondrial-proximal ER membranes through autophagy with the help of RTN3L. We propose to call this type of selective autophagy “MAM-phagy”.

scholarly journals The Small GTPase Cdc42 Interacts with Niemann-Pick C1-like 1 (NPC1L1) and Controls Its Movement from Endocytic Recycling Compartment to Plasma Membrane in a Cholesterol-dependent Manner

2011 ◽  
Vol 286 (41) ◽  
pp. 35933-35942 ◽  
Author(s):  
Chang Xie ◽  
Na Li ◽  
Zheng-Jun Chen ◽  
Bo-Liang Li ◽  
Bao-Liang Song
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Protein ◽  
Small Gtpase ◽  
Cholesterol Depletion ◽  
Mutant Form ◽  
Dependent Manner ◽  
Biliary Cholesterol ◽  
Endocytic Recycling ◽  
Knock Out ◽  
Niemann Pick

Niemann-Pick C1-like 1 (NPC1L1) is a multi-transmembrane protein that mediates the absorption of dietary and biliary cholesterol through vesicular endocytosis. The subcellular localization of NPC1L1 is regulated by cholesterol. Cholesterol depletion induces the transport of NPC1L1 to plasma membrane (PM) from endocytic recycling compartment that requires MyoVb·Rab11a·Rab11-FIP2 triple complex, and cholesterol-replenishment renders the internalization of NPC1L1 together with cholesterol. Here, we find that GTP-bound Cdc42 interacts with NPC1L1. Cholesterol depletion regulates the activation of Cdc42 and enhances NPC1L1-Cdc42 interaction. Overexpression of constitutive GTP-bound Cdc42 mutant form or knockdown of Cdc42 inhibits the transport of NPC1L1 to the PM and disturbs the cholesterol-regulated binding of NPC1L1 to Rab11a, MyoVb, and actin. Knockdown of Cdc42 downstream effectors N-WASP or Arp3 also leads to the similar results. In liver-specific Cdc42 knock-out (Cdc42 LKO) mice, NPC1L1 fails to localize to bile canaliculi, and the biliary cholesterol cannot be efficiently reabsorbed. These results indicate that Cdc42 controls the cholesterol-regulated transport and localization of NPC1L1, and plays a role in cholesterol absorption.

scholarly journals Golgi-resident Small GTPase Rab33B Interacts with Atg16L and Modulates Autophagosome Formation

2008 ◽  
Vol 19 (7) ◽  
pp. 2916-2925 ◽  
Author(s):  
Takashi Itoh ◽  
Naonobu Fujita ◽  
Eiko Kanno ◽  
Akitsugu Yamamoto ◽  
Tamotsu Yoshimori ◽  
...  
Keyword(s):  
De Novo ◽  
Membrane Dynamics ◽  
Small Gtpase ◽  
Dependent Manner ◽  
Membrane Structures ◽  
Autophagosome Formation ◽  
Membrane Formation ◽  
Double Membrane ◽  
Sequestosome 1 ◽  
Mechanism Of Degradation

Macroautophagy is a mechanism of degradation of cytoplasmic components in all eukaryotic cells. In macroautophagy, cytoplasmic components are wrapped by double-membrane structures called autophagosomes, whose formation involves unique membrane dynamics, i.e., de novo formation of a double-membrane sac called the isolation membrane and its elongation. However, the precise regulatory mechanism of isolation membrane formation and elongation remains unknown. In this study, we showed that Golgi-resident small GTPase Rab33B (and Rab33A) specifically interacts with Atg16L, an essential factor in isolation membrane formation, in a guanosine triphosphate-dependent manner. Expression of a GTPase-deficient mutant Rab33B (Rab33B-Q92L) induced the lipidation of LC3, which is an essential process in autophagosome formation, even under nutrient-rich conditions, and attenuated macroautophagy, as judged by the degradation of p62/sequestosome 1. In addition, overexpression of the Rab33B binding domain of Atg16L suppressed autophagosome formation. Our findings suggest that Rab33 modulates autophagosome formation through interaction with Atg16L.

scholarly journals PINK1 stabilized by mitochondrial depolarization recruits Parkin to damaged mitochondria and activates latent Parkin for mitophagy

2010 ◽  
Vol 189 (2) ◽  
pp. 211-221 ◽  
Author(s):  
Noriyuki Matsuda ◽  
Shigeto Sato ◽  
Kahori Shiba ◽  
Kei Okatsu ◽  
Keiko Saisho ◽  
...  
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Neurodegenerative Disorder ◽  
Dependent Manner ◽  
Key Factors ◽  
Ubiquitin Ligase Activity ◽  
Autophagic Degradation ◽  
Insight Into

Parkinson's disease (PD) is a prevalent neurodegenerative disorder. Recent identification of genes linked to familial forms of PD such as Parkin and PINK1 (PTEN-induced putative kinase 1) has revealed that ubiquitylation and mitochondrial integrity are key factors in disease pathogenesis. However, the exact mechanism underlying the functional interplay between Parkin-catalyzed ubiquitylation and PINK1-regulated mitochondrial quality control remains an enigma. In this study, we show that PINK1 is rapidly and constitutively degraded under steady-state conditions in a mitochondrial membrane potential–dependent manner and that a loss in mitochondrial membrane potential stabilizes PINK1 mitochondrial accumulation. Furthermore, PINK1 recruits Parkin from the cytoplasm to mitochondria with low membrane potential to initiate the autophagic degradation of damaged mitochondria. Interestingly, the ubiquitin ligase activity of Parkin is repressed in the cytoplasm under steady-state conditions; however, PINK1-dependent mitochondrial localization liberates the latent enzymatic activity of Parkin. Some pathogenic mutations of PINK1 and Parkin interfere with the aforementioned events, suggesting an etiological importance. These results provide crucial insight into the pathogenic mechanisms of PD.

scholarly journals Tuba activates Cdc42 during neuronal polarization downstream of the small GTPase Rab8a

2019 ◽  
Author(s):  
Pamela J. Urrutia ◽  
Felipe Bodaleo ◽  
Daniel A. Bórquez ◽  
Victoria Rozes-Salvador ◽  
Cristopher Villablanca ◽  
...  
Keyword(s):  
Small Gtpases ◽  
Membrane Dynamics ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Neuronal Polarity ◽  
Dependent Manner ◽  
Gain Of Function ◽  
Molecular Determinants ◽  
Axon Specification ◽  
Neuronal Polarization

ABSTRACTThe acquisition of neuronal polarity is a complex molecular process that involves several different cellular mechanisms that need to be finely coordinated to define the somatodendritic and axonal compartments. Amongst such mechanisms, cytoskeleton and membrane dynamics control both the morphological transitions that define neuronal polarity acquisition as well as provide molecular determinants to specific sites in neurons at a defined time point. Small GTPases from the Rab and Rho families are well known molecular determinants of neuronal differentiation. However, during axon specification, a molecular link that couples proteins from these two families has yet to be identified. In this paper, we describe the role of Tuba, a Cdc42-specific guanine nucleotide-exchange factor (GEF), in neuronal polarity through a Rab8a-dependent mechanism. Rab8a or Tuba gain-of-function generates neurons with supernumerary axons whereas Rab8a or Tuba loss-of-function abrogated axon specification, phenocopying the well-established effect of Cdc42 on neuronal polarity. Neuronal polarization associated to Rab8a is also evidenced in vivo, since a dominant negative version of Rab8a severely impaired neuronal migration.Remarkably, Rab8a activates Cdc42 in a Tuba-dependent manner, and dominant negative mutants of both GTPases reciprocally prevent the effect over polarity acquisition in the gain-of-function scenarios. Our results strongly suggest that a positive feedback loop linking Rab8a and Cdc42 activities via Tuba, is a primary event in neuronal polarization. In addition, we identified the GEF responsible for Cdc42 activation that is essential to specify axons in cultured neurons.

scholarly journals Cytoplasmic Cargo Receptor p62 Inhibits Avibirnavirus Replication by Mediating Autophagic Degradation of Viral Protein VP2

2020 ◽  
Vol 94 (24) ◽  
Author(s):  
Yahui Li ◽  
Boli Hu ◽  
Gang Ji ◽  
Yina Zhang ◽  
Chenyang Xu ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Viral Protein ◽  
Virus Assembly ◽  
Virus Production ◽  
Degradation Pathway ◽  
Dependent Manner ◽  
Virus Particles ◽  
Selective Autophagy ◽  
Cargo Receptor ◽  
Autophagic Degradation

ABSTRACT Selective autophagy regulates the degradation of cytoplasmic cargos, such as damaged organelles, invading pathogens, and aggregated proteins. Furthermore, autophagy is capable of degrading avibirnavirus, but the mechanism responsible for this process is unclear. Here, we show that autophagy cargo receptor p62 regulates the degradation of the avibirnavirus capsid protein VP2. Binding of p62 to VP2 enhances autophagic induction and promotes autophagic degradation of viral protein VP2. Further study showed that the interaction of p62 with viral protein VP2 is dependent on ubiquitination at the K411 site of VP2 and the ubiquitin-associated domain of p62. Mutation analysis showed that the K411R mutation of viral protein VP2 prohibits its p62-mediated degradation. Consistent with this finding, p62 lacking the ubiquitin-associated domain or the LC3-interacting region no longer promoted the degradation of VP2. Virus production revealed that the knockout of p62 but not the overexpression of p62 promotes the replication of avibirnavirus. Collectively, our findings suggest that p62 mediates selective autophagic degradation of avibirnavirus protein VP2 in a ubiquitin-dependent manner and is an inhibitor of avibirnavirus replication. IMPORTANCE Avibirnavirus causes severe immunosuppression and mortality in young chickens. VP2, the capsid protein of avibirnavirus, is responsible for virus assembly, maturation, and replication. Previous study showed that avibirnavirus particles could be engulfed into the autophagosome and degradation of virus particles took apart. Selective autophagy is a highly specific and regulated degradation pathway for the clearance of damaged or unwanted cytosolic components and superfluous organelles as well as invading microbes. However, whether and how selective autophagy removes avibirnavirus capsids is largely unknown. Here, we have shown that selective autophagy specifically clears ubiquitinated avibirnavirus protein VP2 by p62 recognition and that p62 is an inhibitor of avibirnavirus replication, highlighting the role of p62 as a potential drug target for mediating the removal of ubiquitinated virus components from cells.

scholarly journals EXO70D isoforms mediate selective autophagic degradation of Type-A ARR proteins to regulate cytokinin sensitivity

2020 ◽  
Author(s):  
Atiako Kwame Acheampong ◽  
Carly Shanks ◽  
Chai-Yi Chang ◽  
G. Eric Schaller ◽  
Yasin Dagdas ◽  
...  
Keyword(s):  
Type A ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Response Regulators ◽  
Plant Growth And Development ◽  
Cytokinin Signaling ◽  
Developmental Transitions ◽  
Selective Autophagy ◽  
Autophagic Degradation ◽  
Response To Stress

AbstractThe phytohormone cytokinin influences many aspects of plant growth and development, several of which also involve the cellular process of autophagy, including leaf senescence, nutrient re-mobilization, and developmental transitions. The Arabidopsis type-A Response Regulators (type-A ARR) are negative regulators of cytokinin signaling that are transcriptionally induced in response to cytokinin. Here, we describe a mechanistic link between cytokinin signaling and autophagy, demonstrating that plants modulate cytokinin sensitivity through autophagic regulation of type-A ARR proteins. Type-A ARR proteins were degraded by autophagy in an AUTOPHAGY-RELATED (ATG)5-dependent manner. EXO70D family members interacted with Type-A ARR proteins, likely in a phosphorylation-dependent manner, and recruited them to autophagosomes via interaction with the core autophagy protein, ATG8. Consistently, loss-of-function exo70D1,2,3 mutants compromised targeting of type-A ARRs to autophagic vesicles, have elevated levels of type-A ARR proteins, and are hyposensitive to cytokinin. Disruption of both type-A ARRs and EXO70D1,2,3 compromised survival in carbon-deficient conditions, suggesting interaction between autophagy and cytokinin responsiveness in response to stress. These results indicate that the EXO70D proteins act as selective autophagy receptors to target type-A ARR cargos for autophagic degradation, demonstrating that cytokinin signaling can be modulated by selective autophagy.

The F-box E3 ubiquitin ligase BAF1 mediates the degradation of the brassinosteroid-activated transcription factor BES1 through selective autophagy in Arabidopsis

2021 ◽  
Author(s):  
Ping Wang ◽  
Trevor M Nolan ◽  
Natalie M Clark ◽  
Hao Jiang ◽  
Christian Montes-Serey ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Ubiquitin Ligase ◽  
Stress Responses ◽  
E3 Ubiquitin Ligase ◽  
Dependent Manner ◽  
Selective Autophagy ◽  
Sucrose Starvation ◽  
Autophagic Degradation ◽  
Autophagy Pathway

Abstract Brassinosteroids (BRs) regulate plant growth, development, and stress responses by activating the core transcription factor BRI1-EMS-SUPPRESSOR1 (BES1), whose degradation occurs through the proteasome and autophagy pathways. The E3 ubiquitin ligase(s) that modify BES1 for autophagy-mediated degradation remain to be fully defined. Here, we identified an F-box family E3 ubiquitin ligase named BES1-ASSOCIATED F-BOX1 (BAF1) in Arabidopsis thaliana. BAF1 interacts with BES1 and mediates its ubiquitination and degradation. Our genetic data demonstrated that BAF1 inhibits BR signaling in a BES1-dependent manner. Moreover, BAF1 targets BES1 for autophagic degradation in a selective manner. BAF1-triggered selective autophagy of BES1 depends on the ubiquitin binding receptor DOMINANT SUPPRESSOR OF KAR2 (DSK2). Sucrose starvation-induced selective autophagy of BES1, but not bulk autophagy, was significantly compromised in baf1 mutant and BAF1-ΔF (BAF1 F-box decoy) overexpression plants, but clearly increased by BAF1 overexpression. The baf1 and BAF1-ΔF overexpression plants had increased BR-regulated growth but were sensitive to long-term sucrose starvation, while BAF1 overexpression plants had decreased BR-regulated growth but were highly tolerant of sucrose starvation. Our results not only established BAF1 as an E3 ubiquitin ligase that targets BES1 for degradation through selective autophagy pathway, but also revealed a mechanism for plants to reduce growth during sucrose starvation.

scholarly journals Vac8 Controls Vacuolar Membrane Dynamics during Different Autophagy Pathways in Saccharomyces cerevisiae

Cells ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 661 ◽  
Author(s):  
Boutouja ◽  
Stiehm ◽  
Reidick ◽  
Mastalski ◽  
Brinkmeier ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Building Blocks ◽  
Growth Conditions ◽  
Membrane Dynamics ◽  
Dependent Manner ◽  
Characteristic Appearance ◽  
Yeast Vacuole ◽  
Plant Vacuole ◽  
Autophagic Degradation

The yeast vacuole is a vital organelle, which is required for the degradation of aberrant intracellular or extracellular substrates and the recycling of the resulting nutrients as newly available building blocks for the cellular metabolism. Like the plant vacuole or the mammalian lysosome, the yeast vacuole is the destination of biosynthetic trafficking pathways that transport the vacuolar enzymes required for its functions. Moreover, substrates destined for degradation, like extracellular endocytosed cargoes that are transported by endosomes/multivesicular bodies as well as intracellular substrates that are transported via different forms of autophagosomes, have the vacuole as destination. We found that non-selective bulk autophagy of cytosolic proteins as well as the selective autophagic degradation of peroxisomes (pexophagy) and ribosomes (ribophagy) was dependent on the armadillo repeat protein Vac8 in Saccharomyces cerevisiae. Moreover, we showed that pexophagy and ribophagy depended on the palmitoylation of Vac8. In contrast, we described that Vac8 was not involved in the acidification of the vacuole nor in the targeting and maturation of certain biosynthetic cargoes, like the aspartyl-protease Pep4 (PrA) and the carboxy-peptidase Y (CPY), indicating a role of Vac8 in the uptake of selected cargoes. In addition, we found that the hallmark phenotype of the vac8 strain, namely the characteristic appearance of fragmented and clustered vacuoles, depended on the growth conditions. This fusion defect observed in standard glucose medium can be complemented by the replacement with oleic acid or glycerol medium. This complementation of vacuolar morphology also partially restores the degradation of peroxisomes. In summary, we found that Vac8 controlled vacuolar morphology and activity in a context- and cargo-dependent manner.

scholarly journals EXO70D isoforms mediate selective autophagic degradation of type-A ARR proteins to regulate cytokinin sensitivity

2020 ◽  
Vol 117 (43) ◽  
pp. 27034-27043
Author(s):  
Atiako Kwame Acheampong ◽  
Carly Shanks ◽  
Chia-Yi Cheng ◽  
G. Eric Schaller ◽  
Yasin Dagdas ◽  
...  
Keyword(s):  
Type A ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Response Regulators ◽  
Cytokinin Signaling ◽  
Developmental Transitions ◽  
Selective Autophagy ◽  
Receiver Domain ◽  
Autophagic Degradation ◽  
Response To Stress

The phytohormone cytokinin influences many aspects of plant growth and development, several of which also involve the cellular process of autophagy, including leaf senescence, nutrient remobilization, and developmental transitions. The Arabidopsis type-A response regulators (type-A ARR) are negative regulators of cytokinin signaling that are transcriptionally induced in response to cytokinin. Here, we describe a mechanistic link between cytokinin signaling and autophagy, demonstrating that plants modulate cytokinin sensitivity through autophagic regulation of type-A ARR proteins. Type-A ARR proteins were degraded by autophagy in an AUTOPHAGY-RELATED (ATG)5-dependent manner, and this degradation is promoted by phosphorylation on a conserved aspartate in the receiver domain of the type-A ARRs. EXO70D family members interacted with type-A ARR proteins, likely in a phosphorylation-dependent manner, and recruited them to autophagosomes via interaction of the EXO70D AIM with the core autophagy protein, ATG8. Consistently, loss-of-function exo70D1,2,3 mutants exhibited compromised targeting of type-A ARRs to autophagic vesicles, have elevated levels of type-A ARR proteins, and are hyposensitive to cytokinin. Disruption of both type-A ARRs and EXO70D1,2,3 compromised survival in carbon-deficient conditions, suggesting interaction between autophagy and cytokinin responsiveness in response to stress. These results indicate that the EXO70D proteins act as selective autophagy receptors to target type-A ARR cargos for autophagic degradation, demonstrating modulation of cytokinin signaling by selective autophagy.

scholarly journals An endoplasmic reticulum (ER) ATPase safeguards ER identity by removing ectopically localized mitochondrial proteins

2020 ◽  
Author(s):  
Qing Qin ◽  
Ting Zhao ◽  
Wei Zou ◽  
Kang Shen ◽  
Xiangming Wang
Keyword(s):  
Mitochondrial Membrane ◽  
Mitochondrial Proteins ◽  
Dependent Manner ◽  
Related Protein ◽  
C Elegans ◽  
Dendrite Development ◽  
Dendritic Arbors ◽  
Dendrite Morphogenesis ◽  
Surveillance Mechanism ◽  
Er Membrane

SUMMARYStringent targeting of membrane proteins to corresponding organelles is essential for organelle identity and functions. In addition to molecular pathways that target proteins to appropriate organelles, surveillance mechanisms clear mistargeted proteins from undesired destinations. While Msp1 functions on mitochondrial membrane to remove mistargeted proteins, the surveillance mechanism for the ER is not well understood. Here, we show that mitochondrial tail-anchored (TA) and signal-anchored (SA) proteins mislocalize to ER membrane in neurons and muscles in C. elegans catp-8 mutants. catp-8 encodes a conserved P5A type ATPase, which localizes to ER and removes ectopic mitochondrial TA/SA proteins from ER. In catp-8 mutant, mitochondria fission protein FIS-1 mislocalizes to ER membrane. Together with another mitochondria fission protein MFF-2, FIS-1 causes ER fragmentation in a Dynamin related protein (DRP-1) dependent manner. Additionally, CATP-8 is essential for dendrite development. catp-8 mutant dramatically reduces the level of the dendrite guidance receptor DMA-1, leading to diminished dendritic arbors. Hence, P5A ATPase safeguards ER morphology and functions by preventing mitochondrial proteins mislocalization.HIGHLIGHTSCATP-8, a P5A type ATPase, localizes to ER and functions as a surveillance mechanism to remove mistargeted mitochondrial proteins.Multiple mitochondria proteins are mistargeted to ER in catp-8 mutants.Ectopic recruitment of mitochondria fission mechinary to ER causes ER fragmentation in catp-8 mutants.CATP-8 is essential for PVD dendrite morphogenesis through modulating the level of transmembrane receptor DMA-1.

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