Editors' ChoiceProtein Domains

It Takes Two to Make a PH Domain

Science's STKE  08 Mar 2005:
Vol. 2005, Issue 274, pp. tw84
DOI: 10.1126/stke.2742005tw84

Pleckstrin homology (PH) domains confer specific lipid-binding properties to the proteins in which they are found. Not all PH domains are readily identifiable through available sequence-analysis methods: Some are discontinuous with the N- and C-terminal portions of the PH domain separated within the molecule, and some are formed by nonconsensus sequences that can adopt a PH-like structure. Van Rossum et al. report that TRPC3 (a member of the transient receptor potential protein family of cation channels) and phospholipase C-γ1 (PLC-γ1) interact to form an intermolecular PH-like domain that controls plasma membrane expression of the TRPC3 channel through binding to specific lipids. TRPC3 interacts with a C-terminal portion of a partial PH domain in PLC-γ1, called PH-c. The authors developed an algorithm that slides a partial consensus sequence across a target protein and then uses PH domain complementation to detect PH-like domains. This method identified the residues of TRPC3 that are known to bind PLC-γ1, as well as unconventional PH domains in several other proteins known to form a PH-like structure. In vitro translated PLC-γ1 PH-c peptide and wild-type or mutant TRPC3 that could not bind PLC-γ1 PH-c were analyzed for lipid binding. Only in the presence of both wild-type TRPC3 and PLC-γ1 PH-c was binding to phosphatidylinositol 4,5 bisphosphate (PI4,5P2) detected. The activity and surface expression of TRPC3 in transfected cells required both PLC-γ1 binding and lipid binding, because mutations that disrupted either decreased channel activity and abundance at the cell surface. This provides evidence that an intermolecular lipid-binding PH domain controls surface expression of TRPC3. The formation of intermolecular PH domains provides a model for lipid regulation of other proteins that lack conventional PH domains, and the algorithm provides a mechanism to detect these "invisible" PH domains.

D. B. van Rossum, R. L. Patterson, S. Sharma, R. K. Barrow, M. Kornberg, D. L. Gill, S. H. Snyder, Phospholipase Cγ1 controls surface expression of TRPC3 through an intermolecular PH domain. Nature 434, 99-104 (2005). [PubMed]