scholarly journals Distinct Roles for Tsg101 and Hrs in Multivesicular Body Formation and Inward Vesiculation

2006 ◽  
Vol 17 (8) ◽  
pp. 3469-3483 ◽  
Author(s):  
M. Razi ◽  
C. E. Futter
Keyword(s):  
Growth Factor ◽  
Mammalian Cells ◽  
Susceptibility Gene ◽  
Growth Factor Receptor ◽  
Multivesicular Body ◽  
Early Endosome ◽  
Endosomal Sorting ◽  
Epidermal Growth ◽  
Tumor Susceptibility Gene ◽  
Hepatocyte Growth

In mammalian cells, epidermal growth factor (EGF) stimulation promotes multivesicular body (MVB) formation and inward vesiculation within MVB. Annexin 1 is required for EGF-stimulated inward vesiculation but not MVB formation, demonstrating that MVB formation (the number of MVBs/unit cytoplasm) and inward vesiculation (the number of internal vesicles/MVB) are regulated by different mechanisms. Here, we show that EGF-stimulated MVB formation requires the tumor susceptibility gene, Tsg101, a component of the ESCRT (endosomal sorting complex required for transport) machinery. Depletion of Tsg101 potently inhibits EGF degradation and MVB formation and causes the vacuolar domains of the early endosome to tubulate. Although Tsg101 depletion inhibits MVB formation and alters the morphology of the early endosome in unstimulated cells, these effects are much greater after EGF stimulation. In contrast, depletion of hepatocyte growth factor receptor substrate (Hrs) only modestly inhibits EGF degradation, does not induce tubulation of the early endosome, and causes the generation of enlarged MVBs that retain the ability to fuse with the lysosome. Together, these results indicate that Tsg101 is required for the formation of stable vacuolar domains within the early endosome that develop into MVBs and Hrs is required for the accumulation of internal vesicles within MVBs and that both these processes are up-regulated by EGF stimulation.

scholarly journals VPS37A directs ESCRT recruitment for phagophore closure

2019 ◽  
Vol 218 (10) ◽  
pp. 3336-3354 ◽  
Author(s):  
Yoshinori Takahashi ◽  
Xinwen Liang ◽  
Tatsuya Hattori ◽  
Zhenyuan Tang ◽  
Haiyan He ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Growth Factor Receptor ◽  
Multivesicular Body ◽  
Regulatory Mechanisms ◽  
Endosomal Sorting ◽  
Aaa Atpase ◽  
Escrt Machinery ◽  
Genome Wide ◽  
A Genome ◽  
Epidermal Growth

The process of phagophore closure requires the endosomal sorting complex required for transport III (ESCRT-III) subunit CHMP2A and the AAA ATPase VPS4, but their regulatory mechanisms remain unknown. Here, we establish a FACS-based HaloTag-LC3 autophagosome completion assay to screen a genome-wide CRISPR library and identify the ESCRT-I subunit VPS37A as a critical component for phagophore closure. VPS37A localizes on the phagophore through the N-terminal putative ubiquitin E2 variant domain, which is found to be required for autophagosome completion but dispensable for ESCRT-I complex formation and the degradation of epidermal growth factor receptor in the multivesicular body pathway. Notably, loss of VPS37A abrogates the phagophore recruitment of the ESCRT-I subunit VPS28 and CHMP2A, whereas inhibition of membrane closure by CHMP2A depletion or VPS4 inhibition accumulates VPS37A on the phagophore. These observations suggest that VPS37A coordinates the recruitment of a unique set of ESCRT machinery components for phagophore closure in mammalian cells.

scholarly journals STAM Proteins Bind Ubiquitinated Proteins on the Early Endosome via the VHS Domain and Ubiquitin-interacting Motif

2003 ◽  
Vol 14 (9) ◽  
pp. 3675-3689 ◽  
Author(s):  
Emi Mizuno ◽  
Kensuke Kawahata ◽  
Masaki Kato ◽  
Naomi Kitamura ◽  
Masayuki Komada
Keyword(s):  
Growth Factor ◽  
Growth Factor Receptor ◽  
Binding Activity ◽  
Early Endosome ◽  
Ubiquitinated Proteins ◽  
Ubiquitin Binding ◽  
Cargo Proteins ◽  
Epidermal Growth ◽  
Vhs Domain ◽  
Hepatocyte Growth

Conjugation with ubiquitin acts as a sorting signal for proteins in the endocytic and biosynthetic pathways at the endosome. Signal-transducing adaptor molecule (STAM) proteins, STAM1 and STAM2, are associated with hepatocyte growth factor-regulated substrate (Hrs) but their function remains unknown. Herein, we show that STAM proteins bind ubiquitin and ubiquitinated proteins and that the tandemly located VHS (Vps27/Hrs/STAM) domain and ubiquitin-interacting motif serve as the binding site(s). STAM proteins colocalize with Hrs on the early endosome. Overexpression of STAM proteins, but not their mutants lacking the ubiquitin-binding activity, causes the accumulation of ubiquitinated proteins and ligand-activated epidermal growth factor receptor on the early endosome. These results suggest that through interaction with ubiquitinated cargo proteins on the early endosome via the VHS domain and ubiquitin-interacting motif, STAM proteins participate in the sorting of cargo proteins for trafficking to the lysosome.

ESCRT proteins, endosome organization and mitogenic receptor down-regulation

2009 ◽  
Vol 37 (1) ◽  
pp. 146-150 ◽  
Author(s):  
Philip Woodman
Keyword(s):  
Growth Factor Receptor ◽  
Multivesicular Body ◽  
Early Endosome ◽  
Tyrosine Kinase Receptors ◽  
Physical Separation ◽  
Endosomal Sorting ◽  
Associated Proteins ◽  
Epidermal Growth ◽  
Detailed Function ◽  
Subsequent Incorporation

Mitogenic tyrosine kinase receptors such as the EGFR (epidermal growth factor receptor) are endocytosed once they are activated at the cell surface. After reaching the early endosome, they are ubiquitinated within their cytosolic domain and are consequently sorted away from recycling receptors. They are then incorporated into intraluminal vesicles within the MVB (multivesicular body) en route to the lysosome, where they are degraded. MVB formation requires the stabilization of the vacuolar domain of the early endosome, the segregation of degradative cargo within this domain (with subsequent incorporation of receptors such as EGFR into intraluminal vesicles) and the physical separation and movement of this domain away from the tubular regions of the early endosome. How these different aspects of MVB biogenesis are coupled is unknown, but ESCRTs (endosomal sorting complexes required for transport) have been identified as key molecular players in driving mitogenic receptor sequestration and formation of intraluminal vesicles. The present review summarizes recent findings within the field and from our laboratory regarding the detailed function of ESCRTs and associated proteins in driving the ubiquitin-dependent sorting of EGFR and in maintaining the domain organization of the early endosome.

scholarly journals The ESCRT-III Subunit hVps24 Is Required for Degradation but Not Silencing of the Epidermal Growth Factor Receptor

2006 ◽  
Vol 17 (6) ◽  
pp. 2513-2523 ◽  
Author(s):  
Kristi G. Bache ◽  
Susanne Stuffers ◽  
Lene Malerød ◽  
Thomas Slagsvold ◽  
Camilla Raiborg ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Egf Receptor ◽  
Susceptibility Gene ◽  
Growth Factor Receptor ◽  
Mitogen Activated Protein Kinase ◽  
Endosomal Sorting ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Epidermal Growth

The endosomal sorting complexes required for transport, ESCRT-I, -II, and -III, are thought to mediate the biogenesis of multivesicular endosomes (MVEs) and endosomal sorting of ubiquitinated membrane proteins. Here, we have compared the importance of the ESCRT-I subunit tumor susceptibility gene 101 (Tsg101) and the ESCRT-III subunit hVps24/CHMP3 for endosomal functions and receptor signaling. Like Tsg101, endogenous hVps24 localized mainly to late endosomes. Depletion of hVps24 by siRNA showed that this ESCRT subunit, like Tsg101, is important for degradation of the epidermal growth factor (EGF) receptor (EGFR) and for transport of the receptor from early endosomes to lysosomes. Surprisingly, however, whereas depletion of Tsg101 caused sustained EGF activation of the mitogen-activated protein kinase pathway, depletion of hVps24 had no such effect. Moreover, depletion of Tsg101 but not of hVps24 caused a major fraction of internalized EGF to accumulate in nonacidified endosomes. Electron microscopy of hVps24-depleted cells showed an accumulation of EGFRs in MVEs that were significantly smaller than those in control cells, probably because of an impaired fusion with lyso-bisphosphatidic acid-positive late endosomes/lysosomes. Together, our results reveal functional differences between ESCRT-I and ESCRT-III in degradative protein trafficking and indicate that degradation of the EGFR is not required for termination of its signaling.

An epidermal growth factor receptor/ret chimera generates mitogenic and transforming signals: evidence for a ret-specific signaling pathway

1994 ◽  
Vol 14 (1) ◽  
pp. 663-675
Author(s):  
M Santoro ◽  
W T Wong ◽  
P Aroca ◽  
E Santos ◽  
B Matoskova ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Tyrosine Kinases ◽  
Mammalian Cells ◽  
Egf Receptor ◽  
Biological Effects ◽  
Ectopic Expression ◽  
Growth Factor Receptor ◽  
Dependent Signal ◽  
Epidermal Growth

A chimeric expression vector which encoded for a molecule encompassing the extracellular domain of the epidermal growth factor (EGF) receptor (EGFR) and the intracellular domain of the ret kinase (EGFR/ret chimera) was generated. Upon ectopic expression in mammalian cells, the EGFR/ret chimera was correctly synthesized and transported to the cell surface, where it was shown capable of binding EGF and transducing an EGF-dependent signal intracellularly. Thus, the EGFR/ret chimera allows us to study the biological effects and biochemical activities of the ret kinase under controlled conditions of activation. Comparative analysis of the growth-promoting activity of the EGFR/ret chimera expressed in fibroblastic or hematopoietic cells revealed a biological phenotype clearly distinguishable from that of the EGFR, indicating that the two kinases couple with mitogenic pathways which are different to some extent. Analysis of biochemical pathways implicated in the transduction of mitogenic signals also evidenced significant differences between the ret kinase and other receptor tyrosine kinases. Thus, the sum of our results indicates the existence of a ret-specific pathway of mitogenic signaling.

scholarly journals Hepatocyte Growth Factor Induces Resistance to Anti-Epidermal Growth Factor Receptor Antibody in Lung Cancer

2012 ◽  
Vol 7 (2) ◽  
pp. 272-280 ◽  
Author(s):  
Tadaaki Yamada ◽  
Shinji Takeuchi ◽  
Kenji Kita ◽  
Hideaki Bando ◽  
Takahiro Nakamura ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Growth Factor Receptor ◽  
Receptor Antibody ◽  
Epidermal Growth ◽  
Hepatocyte Growth
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