SPFH2 mediates the endoplasmic reticulum-associated degradation of inositol 1,4,5-trisphosphate receptors and other substrates in mammalian cells.
Inositol 1,4,5-trisphosphate (IP(3)) receptors are endoplasmic reticulum (ER) membrane calcium channels that, upon activation, become substrates for the ER-associated degradation (ERAD) pathway. Although it is clear that IP(3) receptors are polyubiquitinated upon activation and are transferred to the proteasome by a p97-based complex, currently nothing is known about the proteins that initially select activated IP(3) receptors for ERAD. Here, we sought to identify novel proteins that associate with and mediate the ERAD of endogenous activated IP(3) receptors. SPFH2, an uncharacterized SPFH domain-containing protein, rapidly associated with IP(3) receptors in a manner that preceded significant polyubiquitination and the association of p97 and related proteins. SPFH2 was found to be an ER membrane protein largely residing within the ER lumen and in resting and stimulated cells was linked to ERAD pathway components, apparently via endogenous substrates undergoing degradation. Suppression of SPFH2 expression by RNA interference markedly inhibited IP(3) receptor polyubiquitination and degradation and the processing of other ERAD substrates. Overall, these studies identify SPFH2 as a key ERAD pathway component and suggest that it may act as a substrate recognition factor.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.