title: CapZ dynamics are altered by endothelin-1 and phenylephrine via PIP2- and PKC-dependent mechanisms.
abstract: One of the unanswered questions in muscle hypertrophy is how new contractile units are inserted into a stable existing cytoskeletal meshwork. Regulation of actin capping by CapZ may play a role in remodeling processes, therefore, CapZ dynamics are determined during rapid growth of cardiac cells in vitro. Neonatal rat ventricular myocytes were infected with adenovirus expressing green fluorescent protein-CapZ beta1 and responded normally to hypertrophic stimuli. CapZ dynamics were analyzed by fluorescence recovery after photobleaching in cultured myocytes treated with endothelin-1 (100 nM) or phenylephrine (10 muM). Recovery by 30 s was greater with endothelin treatment. Analysis 30 min postbleach showed CapZ-infected cells treated with endothelin recovered more completely than controls (77 +/- 9% vs. 50 +/- 6%, P < 0.001). Similar results were found with phenylephrine (77 +/- 5%, P < 0.05). A potential mechanism for phosphatidylinositol bisphosphate (PIP2) mediation of increased CapZ exchange in endothelin- and phenylephrine-treated cells was tested. PIP2 sequestration with neomycin (500 muM) blocked both endothelin- (43 +/- 6%, P < 0.001) and phenylephrine (36 +/- 4%, P < 0.001)-mediated recovery. The protein kinase C inhibitor chelerythrine chloride (10 muM) also blocked endothelin- (53 +/- 10%, P < 0.001) and phenylephrine (42 +/- 3%, P < 0.001)-mediated recovery. This study demonstrates for the first time that endothelin and phenylephrine alter CapZ dynamics through PIP2- and PKC-dependent pathways, which might destabilize the existing framework and permit sarcomeric remodelling to proceed.
authors.affiliation: Dept. of Physiology and Biophysics, University of Illinois, Chicago, IL 60612, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Hartman
authors.forename: Jody L
authors.initials: JL
authors.lastname: Martin
authors.forename: R John
authors.initials: RJ
authors.lastname: Solaro
authors.forename: Allen M
authors.initials: AM
authors.lastname: Samarel
authors.forename: Brenda
authors.initials: B
authors.lastname: Russell
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology; D051347:CapZ Actin Capping Protein / Q000235:genetics / Q000378:metabolism*; D006332:Cardiomegaly / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology*; D036681:Fluorescence Recovery After Photobleaching; D049452:Green Fluorescent Proteins / Q000235:genetics; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D009355:Neomycin / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000201:enzymology
chemical_list: D053119:Benzophenanthridines; D051347:CapZ Actin Capping Protein; D002316:Cardiotonic Agents; D019332:Endothelin-1; D019269:Phosphatidylinositol 4,5-Diphosphate; D011500:Protein Synthesis Inhibitors; D049452:Green Fluorescent Proteins; D010656:Phenylephrine; C016299:chelerythrine; D011493:Protein Kinase C; D009355:Neomycin