Shim, J. H. et al. CHMP5 is essential for late endosome function and down-regulation of receptor signaling during mouse embryogenesis. J. Cell Biol. 172, 1045-1056

Section of Immunobiology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520, USA.
The Journal of Cell Biology (Impact Factor: 9.83). 04/2006; 172(7):1045-56. DOI: 10.1083/jcb.200509041
Source: PubMed


Charged MVB protein 5 (CHMP5) is a coiled coil protein homologous to the yeast Vps60/Mos10 gene and other ESCRT-III complex members, although its precise function in either yeast or mammalian cells is unknown. We deleted the CHMP5 gene in mice, resulting in a phenotype of early embryonic lethality, reflecting defective late endosome function and dysregulation of signal transduction. Chmp5-/- cells exhibit enlarged late endosomal compartments that contain abundant internal vesicles expressing proteins that are characteristic of late endosomes and lysosomes. This is in contrast to ESCRT-III mutants in yeast, which are defective in multivesicular body (MVB) formation. The degradative capacity of Chmp5-/- cells was reduced, and undigested proteins from multiple pathways accumulated in enlarged MVBs that failed to traffic their cargo to lysosomes. Therefore, CHMP5 regulates late endosome function downstream of MVB formation, and the loss of CHMP5 enhances signal transduction by inhibiting lysosomal degradation of activated receptors.

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    • "Endocytic downregulation of cell surface receptors is thought to be a key regulatory step in establishing the appropriate extent of signaling. Indeed, disruption of late endosome/multivesicular body (MVB) function by small interfering RNA (siRNA)-mediated suppression of Chmp5, a subunit of the MVB-forming complex, i.e., endosomal sorting complex required for transport III (ESCRT-III), results in defective silencing of RTKs and TGF-b signaling (Shim et al., 2006 "
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    ABSTRACT: The embryonic body plan is established through positive and negative control of various signaling cascades. Late endosomes and lysosomes are thought to terminate signal transduction by compartmentalizing the signaling molecules; however, their roles in embryogenesis remain poorly understood. We showed here that the endocytic pathway participates in the developmental program by regulating the signaling activity. We modified the mouse Vam2 (mVam2) locus encoding a regulator of membrane trafficking. mVam2-deficient cells exhibited abnormally fragmented late endosomal compartments. The mutant cells could terminate signaling after the removal of the growth factors including TGF-β and EGF, except BMP-Smad1/Smad5 signaling. mVam2-deficient embryos exhibited ectopic activation of BMP signaling and disorganization of embryo patterning. We found that mVam2, which interacts with BMP type I receptor, is required for the spatiotemporal modulation of BMP signaling, via sequestration of the receptor complex in the late stages of the endocytic pathway.
    Full-text · Article · Jun 2012 · Developmental Cell
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    • "It plays a crucial role in sorting membrane proteins that are destined for degradation or routing to the lysosome3, 4. These proteins, such as activated growth-factor, hormone and cytokine receptors, are internalized into vesicles forming an MVB, the contents of the MVB are then transferred to lysosomes for degradation2, 5, 6. CHMP5 is responsible for the final conversion of late endosomal MVB to lysosomes and plays a critical role in the downregulation of signaling pathways through receptor degradation2, 7. "
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    ABSTRACT: Over-expressed CHMP5 was found to act as oncogene that probably participated in leukemogenesis. In this study, we constructed the CHMP5 single chain variable fragment antibody (CHMP5-scFv) retrovirus and studied the changes of programmed cell death (PCD) of AML leukemic cells after infection by the retrovirus. The anti-CHMP5 KC14 hybridoma cell line was constructed to generate monoclonal antibody of CHMP5. The protein expression of CHMP5 was studied using immunofluorescence analysis. pMIG-CHMP5 scFv antibody expressible retroviral vector was constructed to prepare CHMP5-scFv retrovirus. AML leukemic U937 cells were infected with the retrovirus, and programmed cell death was studied using confocal microscope, FCM and Western blot. We obtained a monoclonal antibody of CHMP5, and found the expression of CHMP5 was up-regulated in the leukemic cells. After U937 cells were infected with CHMP5-scFv retrovirus, CHMP5 protein was neutralized. Moreover, the infection resulted in a significant increase in apoptosis and necrosis of U937 cells. In U937 cells infected with CHMP5-scFv retrovirus, apoptosis-inducing factor (AIF)-mediated caspase-independent necrotic PCD was activated, but autophagic programmed cell death was not observed. Neither the intrinsic nor extrinsic apoptotic PCD pathway was activated. The granzyme B/perforin-mediated caspase-dependent apoptotic PCD pathway was not activated. CHMP5-scFv retrovirus can neutralize the abnormally high levels of the CHMP5 protein in the cytosol of AML leukemic U937 cells, thereby inducing the programmed cell death of the leukemic cells via AIF-mediated caspase-independent necrosis and apoptosis.
    Full-text · Article · May 2012 · Acta Pharmacologica Sinica
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    • "Both CHMP5 and CHMP4B C - Terminal Tails Bind Brox Structure 20 , 887 – 898 , May 9 , 2012 ª2012 Elsevier Ltd All rights reserved 893 accumulation of late endosome compartments , and enhanced cell surface receptor signaling due to diminished receptor turn - over , and was embryonically lethal ( Shim et al . , 2006 ) . In addi - tion , CHMP5 was shown to be essential for spindle formation during mitosis and was found to localize at the midbody during cytokinesis , suggesting its broad participation in cell division ( Morita et al . , 2010 , 2007 ) . Furthermore , CHMP5 was reported to play a key role in the initiation of innate immune response aga"
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    ABSTRACT: Interactions of the CHMP protein carboxyl terminal tails with effector proteins play important roles in retroviral budding, cytokinesis, and multivesicular body biogenesis. Here we demonstrate that hydrophobic residues at the CHMP4B C-terminal amphipathic α helix bind a concave surface of Brox, a mammalian paralog of Alix. Unexpectedly, CHMP5 was also found to bind Brox and specifically recruit endogenous Brox to detergent-resistant membrane fractions through its C-terminal 20 residues. Instead of an α helix, the CHMP5 C-terminal tail adopts a tandem β-hairpin structure that binds Brox at the same site as CHMP4B. Additional Brox:CHMP5 interface is furnished by a unique CHMP5 hydrophobic pocket engaging the Brox residue Y348 that is not conserved among the Bro1 domains. Our studies thus unveil a β-hairpin conformation of the CHMP5 protein C-terminal tail, and provide insights into the overlapping but distinct binding profiles of ESCRT-III and the Bro1 domain proteins.
    Full-text · Article · Apr 2012 · Structure
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