Abstract
The membrane microdomain (MD), such as detergent‐resistant low‐density membrane microdomain fraction (DRM), has been paid much attention because many signal‐transducing molecules are recovered in this fraction, although precise localization and interactions of these molecules are largely unclear. To identify neuronal MD‐localized proteins, monoclonal antibodies (mAbs) against the DRM‐components of synaptic plasma membrane fraction (SPM) were produced and the antigens were characterized. One of the antigens reacted with two closely positioned bands of about 140 kDa in SDS‐PAGE and the antigen showed age‐dependent localization on DRM. The antigen was immunoprecipitated with the mAb after partial solubilization with 0.6 M NaCl from SPM‐derived DRM and identified as phospholipase Cβ1 through mass analysis. The identity was further confirmed with Western blotting using a specific polyclonal antibody. The enzyme purified from the DRM was activated by the α subunit of trimeric G protein, Gq, expressed in HEK293 cells. The lipid composition of the liposomes affected the enzymatic activity and the addition of NAP‐22, a neuronal DRM‐localized protein, inhibited the activity. These results suggest that there exists a signal‐transducing MD that performs important roles in neuronal functions through PIP~2~ signaling and Ca^2+^ mobilization. © 2007 Wiley‐Liss, Inc.