Protein kinase C phosphorylation of PLCβ1 regulates its cellular localization

Activation of phospholipase C beta (PLC beta) by G proteins leads to a chain of events that result in an increase in intracellular calcium and activation of protein kinase C (PKC). It has been found that PKC phosphorylates PLC beta 1 on S887 in vitro without affecting its enzymatic activity or its ability to be activated by G alpha(q) proteins. To understand whether S887 phosphorylation affects the enzyme's activity in cells, we constructed two mutants that mimic the wild type and PKC-phosphorylated enzymes (S887A and 5887D). We find that these constructs bind similarly to G alpha(q) in vitro. When expressed in HEK293 cells, both mutants associate identically to G alpha(q) in both the basal and stimulated states. Both mutants diffuse with similar rates and also interact identically with another known binding partner, translin-associated factor X (TRAX), which associates with PLC beta 1 in the cytosol and nucleus. However, the two mutants localize differently in the cell. We find that S887A has a much higher nuclear localization than its S887D counterpart both in HEK293 cells and PC12 cells. Our studies suggest that PKC phosphorylation regulates the level of PLC beta 1 cytosolic and nuclear activity by regulating its cellular compartmentalization. (C) 2011 Elsevier Inc. All rights reserved.