EVIDENCE THAT PHOSPHOLIPASE DELTA-1 IS THE EFFECTOR IN THE G(H) (TRANSGLUTAMINASE II)-MEDIATED SIGNALING

A new class of GTP-binding protein transglutaminase II (G(h)) couples to a 69 kDa phospholipase C (PLC). An 8-amino acid region (LeU(665)-Ly s(672)) of the alpha-subunit of G(h) (G alpha(h)) is involved in inter action and activation of PLC, an observation that has now been used to characterize the 69-kDa PLC further. A 20-amino acid peptide 673 corr esponding to Leu(654)-Leu(673) of G alpha(h) was used to prepare an af finity resin. On incubation with a partially purified PLC preparation from rat liver membranes, the affinity resin-bound similar to 69- and 85-kDa proteins were recognized by an antibody to the 69-kDa PLC. Both purified 69-kDa PLC and PLC-delta 1 bound to the affinity resin; more over, antibodies to PLC-delta 1 recognized the 69-kDa PLC, and antibod ies to the 69 kDa PLC recognized PLC-delta 1. A synthetic peptide corr esponding to LeU(661)-Lys(672) of G alpha(h) inhibited the binding of PLC-delta 1 to the affinity resin and also stimulated PLC-delta 1. Rec onstitution of PLC-delta 1 with GTP gamma S (guanosine 5'-3-O-(thio)tr iphosphate)-activated G(h) resulted in activation of PLC-delta 1. Anti bodies to G alpha(h) also coimmunoprecipitated PLC-delta 1 upon activa tion of G(h). These findings indicate that PLC-delta 1 is the effector of G(h)-mediated signaling.