Structure/function analysis of four core ESCRT-III proteins reveals common regulatory role for extreme C-terminal domain.
Endosomal sorting complex required for transport-III (ESCRT-III) is a large complex built from related ESCRT-III proteins involved in multivesicular body biogenesis. Little is known about the structure and function of this complex. Here, we compare four human ESCRT-III proteins - hVps2-1/CHMP2a, hVps24/CHMP3, hVps20/CHMP6, and hSnf7-1/CHMP4a - to each other, studying the effects of deleting predicted alpha-helical domains on their behavior in transfected cells. Surprisingly, removing approximately 40 amino acids from the C-terminus of each protein unmasks a common ability to associate with endosomal membranes and assemble into large polymeric complexes. Expressing these truncated ESCRT-III proteins in cultured cells causes ubiquitinated cargo to accumulate on enlarged endosomes and inhibits viral budding, while expressing full-length proteins does not. hVps2-1/CHMP2a lacking its C-terminal 42 amino acids further fails to bind to the AAA+ adenosine triphosphatase VPS4B/SKD1, indicating that C-terminal sequences are important for interaction of ESCRT-III proteins with VPS4. Overall, our study supports a model in which ESCRT-III proteins cycle between a default 'closed' state and an activated 'open' state under control of sequences at their C-terminus and associated factors.
Shim
Soomin
S
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Kimpler
Lisa A
LA
Hanson
Phyllis I
PI
D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000737:chemistry / Q000502:physiology; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000502:physiology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000502:physiology*
C498543:CHMP3 protein, human; C481529:CHMP4A protein, human; D056827:Endosomal Sorting Complexes Required for Transport; D009419:Nerve Tissue Proteins; D033921:Vesicular Transport Proteins