Regulation of PLCbeta1a membrane anchoring by its substrate phosphatidylinositol (4,5)-bisphosphate.

Basic knowledge as to the subcellular location and dynamics of PLCbeta isozymes is scant. Here, we report on the subcellular location of GFP-PLCbeta1a and the use of total internal reflection fluorescence (TIRF) microscopy to examine the dynamics of GFP-PLCbeta1a at the plasma membrane upon stimulation of Gq-coupled receptors. Using this technique, we observed PLCbeta1a dissociation from the plasma membrane upon addition of agonist. An increase in intracellular calcium and a decrease in PtdIns(4,5)P2 both coincided with a translocation of PLCbeta1a from the plasma membrane into the cytosol. In order to differentiate between calcium and PtdIns(4,5)P2, rapamycin-induced heterodimerization of FRB and FKBP12 fused to 5-phosphatase IV was used to instantaneously convert PtdIns(4,5)P2 into PtdIns(4)P. Addition of rapamycin caused PLCbeta1a to dissociate from the plasma membrane, indicating that removal of PtdIns(4,5)P2 is sufficient to cause translocation of PLCbeta1a from the plasma membrane. In conclusion, PLCbeta1a localization is regulated by its own substrate.