Regulation of PLCβ1a membrane anchoring by its substrate phosphatidylinositol (4,5)-bisphosphate

Basic knowledge as to the subcellular location and dynamics of PLC beta isozymes is scant. Here, we report on the subcellular location of GFP-PLC beta 1a and the use of total internal reflection fluorescence (TIRF) microscopy to examine the dynamics of GFP-PLC beta 1a at the plasma membrane upon stimulation of Gq-coupled receptors. Using this technique, we observed PLC beta 1a dissociation from the plasma membrane upon addition of agonist. An increase in intracellular calcium and a decrease in PtdIns(4,5)P(2) both coincided with a translocation of PLC beta 1a 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)P(2) into PtdIns(4)P. Addition of rapamycin caused PLC beta 1a to dissociate from the plasma membrane, indicating that removal of PtdIns(4,5)PLC beta 1aP(2) is sufficient to cause translocation of PLC beta 1a from the plasma membrane. In conclusion, PLC beta 1a localization is regulated by its own substrate.