Phospholipase C (PLC)-beta enzymes (isoenzymes beta1-beta4) are activated by G protein subunits, leading to the generation of intracellular messengers which mobilize calcium and activate protein kinase C. It has recently been recognized that these enzymes interact with and are regulated by proteins other than G proteins. Using the east two-hybrid technique to screen a leukocyte library we identified mitogen-activated protein kinase kinase 3 (MKK3) as a partner of PLC-beta2. The interaction was confirmed by co-immunoprecipitation assays which indicated that MKK3 interacts with PLC-beta2, but not with other PLC-betas, PLC-beta2 interacted weakly with MKK6, which is related to MKK3, but not with the other MKK3 tested. The region of PLC-beta2 involved in the interaction with MKK3 was mapped to the C-terminus of PLC-beta2. p38MAPK also co-immunoprecipitated with PLC-beta2. The data suggest that PLC-beta2 serves an unappreciated role assembling components of the p38MAPK signaling module. (C) 2002 Elsevier Science (USA). All rights reserved.