title: ALG-2 activates the MVB sorting function of ALIX through relieving its intramolecular interaction.
abstract: The modular adaptor protein ALIX is critically involved in endosomal sorting complexes required for transport (ESCRT)-mediated multivesicular body (MVB) sorting of activated epidermal growth factor receptor (EGFR); however, ALIX contains a default intramolecular interaction that renders ALIX unable to perform this ESCRT function. The ALIX partner protein ALG-2 is a calcium-binding protein that belongs to the calmodulin superfamily. Prompted by a defined biological function of calmodulin, we determined the role of ALG-2 in regulating ALIX involvement in MVB sorting of activated EGFR. Our results show that calcium-dependent ALG-2 interaction with ALIX completely relieves the intramolecular interaction of ALIX and promotes CHMP4-dependent ALIX association with the membrane. EGFR activation induces increased ALG-2 interaction with ALIX, and this increased interaction is responsible for increased ALIX association with the membrane. Functionally, inhibition of ALIX activation by ALG-2 inhibits MVB sorting of activated EGFR as effectively as inhibition of ALIX interaction with CHMP4 does; however, inhibition of ALIX activation by ALG-2 does not affect cytokinetic abscission or equine infectious anemia virus (EIAV) budding. These findings indicate that calcium-dependent ALG-2 interaction with ALIX is specifically responsible for generating functional ALIX that supports MVB sorting of ubiquitinated membrane receptors.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Sun
authors.affiliation: Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center , Houston, TX, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhou
authors.affiliation: A&G Pharmaceuticals, Inc. , Baltimore, MD, USA.
authors.forename: Joe
authors.initials: J
authors.lastname: Corvera
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA; Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gallick
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA; Department of Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Sue-Hwa
authors.initials: SH
authors.lastname: Lin
authors.affiliation: Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Kuang
keywords: ALG-2; ALIX; CHMP4; EGFR; MVB sorting