Endosomal sorting complexes required for transport (ESCRT-0, -I, -II, -III) execute cargo sorting and intralumenal vesicle (ILV) formation during conversion of endosomes to multivesicular bodies (MVBs). The AAA-ATPase Vps4 regulates the ESCRT-III polymer to facilitate membrane remodeling and ILV scission during MVB biogenesis. Here, we show that the conserved V domain of ESCRT-associated protein Bro1 (the yeast homologue of mammalian proteins ALIX and HD-PTP) directly stimulates Vps4. This activity is required for MVB cargo sorting. Furthermore, the Bro1 V domain alone supports Vps4/ESCRT–driven ILV formation in vivo without efficient MVB cargo sorting. These results reveal a novel activity of the V domains of Bro1 homologues in licensing ESCRT-III–dependent ILV formation and suggest a role in coordinating cargo sorting with membrane remodeling during MVB sorting. Moreover, ubiquitin binding enhances V domain stimulation of Vps4 to promote ILV formation via the Bro1–Vps4–ESCRT-III axis, uncovering a novel role for ubiquitin during MVB biogenesis in addition to facilitating cargo recognition.
Bro1 stimulates Vps4 to promote intralumenal vesicle formation during multivesicular body biogenesis
S. Dean’s present address is Kinesiology, Science Engineering & Mathematics Division, Cornerstone University, Grand Rapids, MI.
I.F. Azmi’s present address is Sherlock Bioscience, Boston, MA.
J. Staffenhagen’s present address is Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN.
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Chun-Che Tseng, Shirley Dean, Brian A. Davies, Ishara F. Azmi, Natalya Pashkova, Johanna A. Payne, Jennifer Staffenhagen, Matt West, Robert C. Piper, Greg Odorizzi, David J. Katzmann; Bro1 stimulates Vps4 to promote intralumenal vesicle formation during multivesicular body biogenesis. J Cell Biol 2 August 2021; 220 (8): e202102070. doi: https://doi.org/10.1083/jcb.202102070
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