Distinct Regulatory Logic Controls Recruitment and Membrane Dynamics of ESCRT-III Subunit Vps60

Endosomal Sorting Complexes Required for Transport (ESCRT) machinery drives membrane remodeling and scission events essential for multivesicular body (MVB) biogenesis. The accessory ESCRT-III subunit Vps60 (mammalian CHMP5) shares structural features with the major polymerizing subunit Snf7, including the capacity to form homopolymers in vitro. Here, we demonstrate in Saccharomyces cerevisiae that Vps60 recruitment and polymerization require conditions that permit Snf7 polymer turnover: Vps60 is largely excluded when Snf7 assembly is absent and when Snf7 disassembly is blocked, consistent with recruitment of Vps60 late in the ESCRT-III cycle to Snf7 assemblies that undergo normal turnover. Structure-function analysis reveals that Vps60 regulation diverges fundamentally from core ESCRT-III subunits: while occlusion of the Vps60 C terminus by a GFP tag drives constitutive membrane association and polymer assembly, C-terminal truncation impairs endosomal recruitment, indicating that the Vps60 C terminus is required for membrane recruitment, in contrast to the autoinhibitory C-terminal domains of core ESCRT-III subunits. A C-terminally tagged Vps60 that constitutively associates with membranes phenocopies loss of Vps60 function in both intralumenal vesicle (ILV) formation and cargo sorting. These findings indicate that despite structural similarity to Snf7, Vps60 functions as a late-arriving accessory factor whose recruitment and assembly are tightly coupled to Snf7 dynamics. [Media: see text] [Media: see text] [Media: see text] [Media: see text].