Conformational Changes in the Endosomal Sorting Complex Required for the Transport III Subunit Ist1 Lead to Distinct Modes of ATPase Vps4 Regulation

• Published in: The Journal of biological chemistry Vol. 290; no. 50; pp. 30053 - 30065
• Main Authors: Tan, Jason, Davies, Brian A., Payne, Johanna A., Benson, Linda M., Katzmann, David J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 11.12.2015; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Triphosphatases - metabolism; ATPase; Did2; endosomal sorting; endosomal sorting complexes required for transport (ESCRT); Endosomal Sorting Complexes Required for Transport - chemistry; Endosomal Sorting Complexes Required for Transport - genetics; Endosomal Sorting Complexes Required for Transport - metabolism; Ist1; Membrane Biology; Mutagenesis, Site-Directed; Protein Conformation; Protein Folding; protein sorting; protein stability; Protein Transport; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - metabolism; Vesicular Transport Proteins - chemistry; Vesicular Transport Proteins - metabolism; Vps4; endosomal sorting complexes required for transport (ESCRT); Did2; Vps4; Ist1; ATPase; protein conformation; protein sorting; endosomal sorting; protein stability
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.665604

Intralumenal vesicle formation of the multivesicular body is a critical step in the delivery of endocytic cargoes to the lysosome for degradation. Endosomal sorting complex required for transport III (ESCRT-III) subunits polymerize on endosomal membranes to facilitate membrane budding away from the cytoplasm to generate these intralumenal vesicles. The ATPase Vps4 remodels and disassembles ESCRT-III, but the manner in which Vps4 activity is coordinated with ESCRT-III function remains unclear. Ist1 is structurally homologous to ESCRT-III subunits and has been reported to inhibit Vps4 function despite the presence of a microtubule-interacting and trafficking domain-interacting motif (MIM) capable of stimulating Vps4 in the context of other ESCRT-III subunits. Here we report that Ist1 inhibition of Vps4 ATPase activity involves two elements in Ist1: the MIM itself and a surface containing a conserved ELYC sequence. In contrast, the MIM interaction, in concert with a more open conformation of the Ist1 core, resulted in stimulation of Vps4. Addition of the ESCRT-III subunit binding partner of Ist1, Did2, also converted Ist1 from an inhibitor to a stimulator of Vps4 ATPase activity. Finally, distinct regulation of Vps4 by Ist1 corresponded with altered ESCRT-III disassembly in vitro. Together, these data support a model in which Ist1-Did2 interactions during ESCRT-III polymerization coordinate Vps4 activity with the timing of ESCRT-III disassembly.