Association of Mammalian Trp4 and Phospholipase C Isozymes with a PDZ Domain-containing Protein, NHERF

Mammalian homologues of DrosophilaTrp have been implicated to form channels that are activated following the depletion of Ca2+ from internal stores. Recent studies indicate that actin redistribution is required for the activation of these channels. Here we show that murine Trp4 and Trp5, as well as phospholipase C β1 and β2 interact with the first PDZ domain of NHERF, regulatory factor of the Na+/H+exchanger. We demonstrated the association of Trp4 and phospholipase C-β1 with NHERF in vivo in an HEK293 cell line expressing Trp4 and in adult mouse brain by immuno-coprecipitation. NHERF is a two PDZ domain-containing protein that associates with the actin cytoskeleton via interactions with members of ezrin/radixin/moesin family. Thus, store-operated channels involving Trp4 and Trp5 can form signaling complexes with phospholipase C isozymes via interactions with NHERF and thereby linking the lipase and the channels to the actin cytoskeleton. The interaction with the PDZ protein may constitute an important mechanism for distribution and regulation of store-operated channels.