Vps4 regulates a subset of protein interactions at the multivesicular endosome

Abstract

During endocytic transport, specific integral membrane proteins are sorted into intraluminal vesicles that bud from the limiting membrane of the endosome. This process, known as multivesicular body (MVB) sorting, is important for several important biological processes. Moreover, components of the MVB sorting machinery are implicated in virus budding. During MVB sorting, a cargo protein recruits components of the MVB sorting machinery from cytoplasmic pools and these sequentially assemble on the endosome. Disassembly of these proteins and recycling into the cytoplasm is critical for MVB sorting. Vacuolar protein sorting 4 (Vps4) is an AAA (ATPase associated with a variety of cellular activities) ATPase which has been proposed to play a critical role in disassembly of the MVB sorting machinery. However, the mechanism by which it disassembles the complex is not clear. Vps4 contains an N‐terminal microtubule interacting and trafficking (MIT) domain, which has previously been shown to be required for recruitment to endosomes, and a single AAA ATPase domain, the activity of which is required for Vps4 function. In this study we have systematically characterized the interaction of Vps4 with other components of the MVB sorting machinery. We demonstrate that Vps4 interacts directly with Vps2 and Bro1. We also show that a subset of Vps4 interactions is regulated by ATP hydrolysis, and one interaction is regulated by ATP binding. Finally, we show that most proteins interact with the Vps4 MIT domain. Our studies indicate that the MIT domain has a dual role in substrate binding and recruitment to endosomes and indicate that Vps4 disassembles the MVB sorting machinery by direct effects on multiple proteins.

Pneumocystis carinii Expresses an Active Rtt109 Histone Acetyltransferase

“…In the future, we plan to isolate Pneumocystis Vps75 and determine if it to can also directly stimulate the Pneumocystis PcRtt109 acetylation of H3-K56. A scan of the available Pneumocystis carinii database revealed no Vps75 homologue, although we did discover a Vps4 yeast homolog that was implicated in multivesicular body sorting and the regulation of cellular sterol metabolism (53,54). The P. carinii Genome Database is only partly (z 50%) complete.…”

Bem3, a Cdc42 GTPase-Activating Protein, traffics to an intracellular compartment and recruits the secretory Rab GTPase Sec4 to endomembranes

“…Moreover, although the early endosomal marker, Snc1, also colocalized substantially ( Fig. 4A; Table 1) with Bem3 in the intracellular compartment, late endosome [Vps21, Markgraf et al, 2009); Vps4 (Vajjhala et al, 2007)] or TGN (Sec7) markers exhibited lower levels of colocalization (Table 1). Surprisingly, we found complete colocalization between the Bem3 compartment and the small Rab GTPase and secretory vesicle marker, Sec4 (Table 1; Fig.…”

The ESCRT-Related CHMP1A and B Proteins Mediate Multivesicular Body Sorting of Auxin Carriers inArabidopsisand Are Required for Plant Development

“…The modulation of Vps4p/SKD1 ATPase activity and its association with endosomes are mediated by accessory proteins, such as CHMP1/Did2p (CHARGED MULTIVESICULAR BODY PROTEIN/CHROMATIN MODIFYING PROTEIN1), LIP5/Vta1p (LYST-INTERACTING PROTEIN 5/VPS TWENTY ASSOCIATED1 PROTEIN), and Vps60p/CHMP5 (Yeo et al, 2003;Scott et al, 2005aScott et al, , 2005bAzmi et al, 2006Azmi et al, , 2008Nickerson et al, 2006;Vajjhala et al, 2007). Did2p in yeast is required for ESCRT-III dissociation from endosomal membranes and directly interacts with the microtubule interacting domain (MIT) of Vps4p/SKD1 via its C-terminal MIT-interacting motive (MIM domain) (Scott et al, 2005a;Obita et al, 2007).…”