| Abstract: | About 25% of the total cellular PLCβ2 content was found to be associated with a sarcolemmal fraction (SARC) isolated from unstimulated porcine trachealis smooth muscle. SARC-associated PLCβ2 was located within two compartments, a detergent-extractable compartment and a nondetergent extractable compartment. SARC PLCβ2 was measured after extraction with 0.6 M KCl; therefore, PLCβ2 was not bound solely by electrostatic forces within either of these compartments. PLCβ2 was shown to translocate from cytosol to SARC during a 20-sec activation of intact muscle with a muscarinic agonist, carbachol (CARB); i.e., cytosolic total PLCβ2 content decreased significantly to 73 ± 7% of control and SARC total PLCβ2 content increased to 180 ± 15% of control value. This translocation was maintained at 5 min of CARB. CARB-evoked translocation occurred into the detergent-extractable SARC fraction, and PLCβ2 content in this fraction increased 300% compared with that in unstimulated muscle. After CARB, SARC PLCβ2 content accounted for >50% of total cellular PLCβ2 content. CARB-evoked increase in PLC activity in SARC paralleled the increase in PLCβ2 content. CARB-induced translocations of PLCβ2 from the cytosol to SARC were of a similar magnitude as occurred with phorbol ester-induced translocations of PKCα. J. Cell. Physiol. 171:271–283, 1997. © 1997 Wiley-Liss, Inc. |
