An essential role of PI(4,5)P2 for maintaining the activity of the transient receptor potential canonical (TRPC)4β

The transient receptor potential canonical 4 (TRPC4) channel is a Ca 2+ -permeable nonselective cation channel in mammalian cells and mediates a number of cellular functions. Many studies show that TRPC channels are activated by stimulation of Gα q -phospholipase C (PLC)-coupled receptors. However, our previous study showed that the TRPC4 current was inhibited by co-expression of a constitutively active form of Gα q (Gα q Q209L ). A shortage of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2 ] in Gα q Q209L may be responsible for reduced TRPC4 activity. Here, we tested this hypothesis by using a rapamycin-inducible system that regulates PI(4,5)P 2 acutely and specifically. Our results showed that the TRPC4β current was reduced by inducible Gα q Q209L , but not by the mutants with impaired binding ability to PLCβ. Depletion of PI(4,5)P 2 by inducing the inositol polyphosphate 5-phosphatase to HEK293 cells that express TRPC4β led to an irreversible inhibition of TRPC4β currents. In contrast, inducing phosphatidylinositol 4-phosphate 5-kinase or intracellular PI(4,5)P 2 application did not activate the TRPC4β current. Finally, we revealed that PI(4,5)P 2 is important in delaying the desensitization of TRPC4β. Taken together, we suggest that PI(4,5)P 2 is not the activator of TRPC4β activation, but it is still necessary for regulating TRPC4β activation.