title: Smooth muscle sarcolemma-associated phospholipase C-beta 2; agonist-evoked translocation.
abstract: About 25% of the total cellular PLC beta 2 content was found to be associated with a sarcolemmal fraction (SARC) isolated from unstimulated porcine trachealis smooth muscle. SARC-associated PLC beta 2 was located 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. PLC beta 2 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 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 CARB. CARB-evoked translocation occurred into the detergent-extractable SARC fraction, and PLC beta 2 content in this fraction increased 300% compared with that in unstimulated muscle. After CARB, SARC PLC beta 2 content accounted for > 50% of total cellular PLC beta 2 content. CARB-evoked increase in PLC activity in SARC paralleled the increase in PLC beta 2 content. CARB-induced translocations of PLC beta 2 from the cytosol to SARC were of a similar magnitude as occurred with phorbol ester-induced translocations of PKC alpha.
authors.affiliation: Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, USA.
authors.forename: R F
authors.initials: RF
authors.lastname: Coburn
authors.forename: E F
authors.initials: EF
authors.lastname: Labelle
authors.forename: T
authors.initials: T
authors.lastname: Griffiths
authors.forename: C B
authors.initials: CB
authors.lastname: Baron
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism*; D018721:Muscarinic Agonists / Q000494:pharmacology; D009130:Muscle, Smooth / Q000201:enzymology* / Q000648:ultrastructure; D054799:Phospholipase C beta; D012508:Sarcolemma / Q000201:enzymology*; D013552:Swine; D014132:Trachea / Q000201:enzymology; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D018721:Muscarinic Agonists; D002217:Carbachol; D010738:Type C Phospholipases; D054799:Phospholipase C beta