SMOOTH-MUSCLE SARCOLEMMA-ASSOCIATED PHOSPHOLIPASE C-BETA(2) - AGONIST-EVOKED TRANSLOCATION

About 25% of the total cellular PLC beta(2) content was found to be as sociated with a sarcolemmal fraction (SARC) isolated from unstimulated porcine trachealis smooth muscle. SARC-associated PLC beta(2) was loc ated within two compartments, a detergent-extractable compartment and a nondetergent extractable compartment. SARC PLC beta(2) was measured after extraction with 0.6 M KCI; therefore, PLC beta(2) was not bound solely by electrostatic forces within either of these compartments. PL C beta(2) was shown to translocate from cytosol to SARC during a 20-se c activation of intact muscle with a muscarinic agonist, carbachol (CA RE); i.e., cytosolic total PLC beta(2) content decreased significantly to 73 +/- 7% of control and SARC total PLC beta(2) content increased to 180 +/- 15% of control value. This translocation was maintained at 5 min of CARE. CARB-evoked translocation occurred into the detergent-e xtractable SARC fraction, and PLC beta(2) content in this fraction inc reased 300% compared with that in unstimulated muscle. After CARE, SAR C PLC beta(2) content accounted for >50% of total cellular PLC beta(2) content. CARE-evoked increase in PLC activity in SARC paralleled the increase in PLC beta(2) content. CARE-induced translocations of PLC be ta(2) from the cytosol to SARC were of a similar magnitude as occurred with phorbol ester-induced translocations of PKC alpha. (C) 1997 Wile y-Liss, Inc.