VCIP135, a novel essential factor for p97/p47-mediated membrane fusion, is required for Golgi and ER assembly in vivo

Abstract

NSF and p97 are ATPases required for the heterotypic fusion of transport vesicles with their target membranes and the homotypic fusion of organelles. NSF uses ATP hydrolysis to dissociate NSF/SNAPs/SNAREs complexes, separating the v- and t-SNAREs, which are then primed for subsequent rounds of fusion. In contrast, p97 does not dissociate the p97/p47/SNARE complex even in the presence of ATP. Now we have identified a novel essential factor for p97/p47-mediated membrane fusion, named VCIP135 (valosin-containing protein [VCP][p97]/p47 complex-interacting protein, p135), and show that it binds to the p97/p47/syntaxin5 complex and dissociates it via p97 catalyzed ATP hydrolysis. In living cells, VCIP135 and p47 are shown to function in Golgi and ER assembly.

Endoplasmic reticulum architecture: structures in flux

“…Subsequent work has confirmed the role of p97 in the dynamics of ER architecture [15,16], but also indicates the participation of additional mechanisms. Thus, antibodies against p97 or its cofactors only partially disrupt ER organization in living cells [17] or in cell-free reconstituted systems [18]. Moreover, S. cerevisiae Cdc48 mutants appear to have normal ER organization [19].…”

Distinct Roles for the AAA ATPases NSF and p97 in the Secretory Pathway

“…More recently, Kondo and coworkers have shown that the p97 adapter proteins p47 and VCIP135 are required in vivo for reassembly of the Golgi apparatus and formation of the ER network upon exit from mitosis (Uchiyama et al, 2002, Uchiyama et al, 2003. Although these studies may point to a specific role for p97 in membrane fusion, both adaptor proteins are also directly linked to ubiquitin pathways.…”

“…Article and publication date are available at www.molbiolcell.org/cgi/doi/10.1091/mbc. E03-02-0097.1997), Ufd1/Npl4 (Meyer et al, 2000(Meyer et al, , 2002, VCIP135 (Uchiyama et al, 2002), and SVIP (Nagahama et al, 2003).…”

“…These include roles in ubiquitin-and proteasome-dependent degradation of cytosolic proteins (Ghislain et al, 1996;Dai et al, 1998;Dai and Li, 2001), ER-associated degradation (ERAD; reviewed in Bays and Hampton, 2002;Tsai et al, 2002), and regulated ubiquitindependent processing (Rape et al, 2001 1997), Ufd1/Npl4 (Meyer et al, 2000(Meyer et al, , 2002, VCIP135 (Uchiyama et al, 2002), and SVIP (Nagahama et al, 2003). Although the mechanism by which AAA ATPases such as NSF and p97 use ATP to modulate the structure of their substrates is not known, the overall homology between these two enzymes makes the idea that they might operate by a similar mechanism attractive.…”

“…The additional finding that p97 could bind to syntaxin 5 in vitro (Rabouille et al, 1998) led to the proposal that p97 might carry out a reaction similar to the SNARE complex disassembly mediated by NSF, but on different SNAREs (Patel et al, 1998;Rabouille et al, 1998). However, although p97 has been shown to release the t-SNARE syntaxin 5 from a complex with p47 and VCIP135 (Uchiyama et al, 2002), it has so far not been found to disassemble complexes consisting of multiple SNARE proteins. Therefore the mechanism by which p97 participates in in vitro fusion reactions remains unknown.…”