Identification of group X secretory phospholipase A(2) as a natural ligandfor mouse phospholipase A(2) receptor

Phospholipase A(2) receptor (PLA(2)R) mediates various biological responses elicited by group IB secretory phospholipase A(2) (sPLA(2)-IB). The recent ly cloned group X sPLA(2) (sPLA(2)-X) possesses several structural features characteristic of sPLA(2)-IB. Here, we detected a specific binding site of sPLA(2)-X in mouse osteoblastic MC3T3-E-1 cells. Cross-linking experiments demonstrated its molecular weight (180 kDa) to be similar to that of PLA(2 )R, In fact, sPLA(2)-X was found to bind the recombinant PLA(2)R expressed in COS-7 cells, and its specific binding detected in mouse lung membranes w as abolished by the deficiency of PLA(2)R. These findings demonstrate sPLA( 2)-X to be one of the high-affinity ligands for mouse PLA(2)R, (C) 2000 Fed eration of European Biochemical Societies. Published by Elsevier Science B. V. All rights reserved.