Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy

Uytterhoeven, Valerie; Lauwers, Elsa; Maes, Ine; Miśkiewicz, Katarzyna; Melo, Manuel N.; Swerts, Jef; Kuenen, Sabine; Wittocx, Rafaël; Corthout, Nikky; Marrink, Siewert J.; Munck, Sebastian; Verstreken, Patrik

doi:10.1016/j.neuron.2015.10.012

Cited by 150 publications

(146 citation statements)

References 78 publications

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“…Late endosomes (LE) also contribute to selective degradation of cytosolic proteins targeted to this compartment by hsc70 through a process known as endosomal microautophagy (e‐MI) (Sahu et al ., 2011; Uytterhoeven et al ., 2015). Using the same N2a cells expressing WT, A152T, and P301L tau, we analyzed changes in cellular levels of these forms of tau upon disrupting e‐MI.…”

Section: Resultsmentioning

confidence: 99%

“…2c). Therefore, we next analyzed possible changes in e‐MI activity in these cells using a reporter developed to study this pathway in flies and modified by our laboratory for use in mammalian cells (Uytterhoeven et al ., 2015). We transduced cells with the split mVenus plasmid containing the N‐terminal and C‐terminal of this protein tagged to the KFERQ motif (N‐KFERQ‐mVenus and C‐KFERQ‐mVenus).…”

Section: Resultsmentioning

confidence: 99%

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Interplay of pathogenic forms of human tau with different autophagic pathways

et al. 2017

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SummaryLoss of neuronal proteostasis, a common feature of the aging brain, is accelerated in neurodegenerative disorders, including different types of tauopathies. Aberrant turnover of tau, a microtubule‐stabilizing protein, contributes to its accumulation and subsequent toxicity in tauopathy patients’ brains. A direct toxic effect of pathogenic forms of tau on the proteolytic systems that normally contribute to their turnover has been proposed. In this study, we analyzed the contribution of three different types of autophagy, macroautophagy, chaperone‐mediated autophagy, and endosomal microautophagy to the degradation of tau protein variants and tau mutations associated with this age‐related disease. We have found that the pathogenic P301L mutation inhibits degradation of tau by any of the three autophagic pathways, whereas the risk‐associated tau mutation A152T reroutes tau for degradation through a different autophagy pathway. We also found defective autophagic degradation of tau when using mutations that mimic common posttranslational modifications in tau or known to promote its aggregation. Interestingly, although most mutations markedly reduced degradation of tau through autophagy, the step of this process preferentially affected varies depending on the type of tau mutation. Overall, our studies unveil a complex interplay between the multiple modifications of tau and selective forms of autophagy that may determine its physiological degradation and its faulty clearance in the disease context.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Interplay of pathogenic forms of human tau with different autophagic pathways

et al. 2017

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“…This process, also recently identified in flies (38), is termed eMI to differentiate it from yeast microautophagy, which is also mediated by microvesicles but independently of ESCRT or hsc70. The current NMR and liposome binding assays pinpoint the lysine cluster (Lys-573, Lys-583, Lys-589, Lys-597, and Lys-601) as the major hsc-70/PS interaction site.…”

Section: Biological Role Of the Hsc-70-ps Complex In Cytosol-to-endosmentioning

confidence: 89%

“…Endosomal microautophagy is an ESCRT-dependent process, which is different from the ESCRT-dependent transport of ubiquitinated plasma membrane proteins into the endosomes, and relies on the cytosolic chaperone hsc-70 for the endosomal internalization of cytosolic proteins (8,38,39). Although hsc-70 can bind misfolded and ubiquitinated proteins, we previously demonstrated that in endosomal microautophagy, hsc-70 also binds proteins with KFERQ motifs.…”

Section: Discussionmentioning

confidence: 99%

Structural and Biological Interaction of hsc-70 Protein with Phosphatidylserine in Endosomal Microautophagy

Morozova¹,

Clement²,

Kaushik

et al. 2016

Journal of Biological Chemistry

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hsc-70 (HSPA8) is a cytosolic molecular chaperone, which plays a central role in cellular proteostasis, including quality control during protein refolding and regulation of protein degradation. hsc-70 is pivotal to the process of macroautophagy, chaperone-mediated autophagy, and endosomal microautophagy. The latter requires hsc-70 interaction with negatively charged phosphatidylserine (PS) at the endosomal limiting membrane. Herein, by combining plasmon resonance, NMR spectroscopy, and amino acid mutagenesis, we mapped the C terminus of the hsc-70 LID domain as the structural interface interacting with endosomal PS, and we estimated an hsc-70/PS equilibrium dissociation constant of 4.7 ؎ 0.1 m. This interaction is specific and involves a total of 4 -5 lysine residues. Plasmon resonance and NMR results were further experimentally validated by hsc-70 endosomal binding experiments and endosomal microautophagy assays. The discovery of this previously unknown contact surface for hsc-70 in this work elucidates the mechanism of hsc-70 PS/membrane interaction for cytosolic cargo internalization into endosomes.hsc-70 (HSPA8) is a constitutively expressed molecular chaperone. The human hsp-70 chaperone family consists of 11 highly homologous members specific to different cellular compartments and organelles (1). hsc-70 resides in the cellular cytosol and nucleus and plays a central role in cellular proteostasis and protein trafficking.Mammalian hsc-70 consists of the following four structural domains: a 44-kDa nucleotide binding domain (NBD) 3 (residues 1-384) with ATPase activity; a 12-kDa substrate binding domain (SBD) that binds to exposed hydrophobic sequences in client proteins (residues 385-505); a 10-kDa helical LID domain (residues 506 -605); and a 5-kDa dynamically unstructured C-terminal domain (CTD) (residues 606 -646) (2). Binding of ATP in the NBD triggers a global conformational change that releases peptide/protein cargo from the SBD (3). Furthermore, hydrolysis of ATP closes the LID and greatly enhances client-SBD affinity (4). This hydrolysis cycle is important in the chaperone activity of hsc-70 as it allows, with the aid of different co-chaperones, iterative binding to clients resulting in protein (re)folding (5). Furthermore, hsc-70 is involved in recruitment of ubiquitin ligases (6), which leads to cargo polyubiquitination and subsequent hsc-70 trafficking to the proteasome or the endocytic pathway for cargo degradation (7).Altogether, hsc-70's multiple interactions allow this chaperone to play an important role in several cellular activities, including ribosomal quality control, protein refolding, proteasome-linked degradation, macroautophagy, endosomal microautophagy, chaperone-mediated autophagy, endoplasmic reticulum/Golgi and mitochondrial targeting, and vesicle clathrin uncoating (8 -17). These activities place hsc-70 as one of the master controllers of cellular proteostasis.To carry out several of these functions, hsc-70 does not only interact with partner proteins but with membrane lipids as ...

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“…However, some cytosolic proteins can also be selectively degraded by eMI after hsc70 binds in their sequence to the same pentapeptide motif previously described for CMA (Figure 4) (8). Hsc70 is not necessary for cargo targeting to microautophagy in yeast, but recent studies support occurrence of hsc70-mediated eMI in Drosophila (88,89). In the following sections, we describe this type of hsc70-dependent eMI in the context of other types of microautophagy and in comparison, with CMA ( Figure 5).…”

Section: Endosomal Microautophagy 31 General Descriptionmentioning

confidence: 93%

Chaperone-mediated autophagy and endosomal microautophagy: Jointed by a chaperone

Tekirdağ

Cuervo

2018

Journal of Biological Chemistry

291

236

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A variety of mechanisms deliver cytosolic materials to the lysosomal compartment for degradation through autophagy. Here, we focus on two autophagic pathways, chaperone-mediated autophagy and endosomal microautophagy that rely on the cytosolic chaperone hsc70 for substrate targeting. Although hsc70 participates in triage of proteins for degradation by different proteolytic systems, the common characteristic shared by these two forms of autophagy, is that hsc70 binds directly to a specific five amino acids motif in the cargo protein for its autophagic targeting. We summarize the current understanding of the molecular machineries behind each of these types of autophagy.

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Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy

Cited by 150 publications

References 78 publications

Interplay of pathogenic forms of human tau with different autophagic pathways

Interplay of pathogenic forms of human tau with different autophagic pathways

Structural and Biological Interaction of hsc-70 Protein with Phosphatidylserine in Endosomal Microautophagy

Chaperone-mediated autophagy and endosomal microautophagy: Jointed by a chaperone

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