title: Myofibrillar and cytoskeletal assembly in neonatal rat cardiac myocytes cultured on laminin and collagen.
abstract: Neonatal rat cardiomyocytes were cultured on extracellular matrix components laminin and collagens I + III to examine effects of extracellular matrix on the assembly of cytoskeletal proteins during myofibrillogenesis. Myofibril assembly was visualized by immunofluorescence of marker proteins for myofibrils (f-actin for I bands and alpha-actinin for Z bands), focal adhesions (vinculin), and transmembrane extracellular matrix receptors (beta 1 integrin) as cells spread for various times in culture. By 4 h in culture, f-actin appeared organized into nonstriated stress-fiber-like structures while alpha-actinin, vinculin and beta 1 integrin were localized in small streaks and beads. Subsequently, striated patterns were observed sequentially in the intracellular cytoskeletal components alpha-actinin, vinculin, f-actin, and then in the transmembrane beta 1 integrin receptor. These data support an earlier model for sarcomerogenesis in which stress-fiber-like structures serve as initial scaffolds upon which alpha-actinin and then vinculin-containing costameres are assembled. This sequential and temporal assembly was the same on both laminin and collagens I + III. A quantitative difference, however, was apparent on the 2 matrices. There was an increased appearance on collagens I + III of rosettes (also called podosomes or cortical actin-containing bodies in other cells) which consisted of an f-actin core surrounded by alpha-actinin, vinculin and beta 1 integrin rims. The increased incidence of rosettes in neonatal myocytes on collagens I + III suggests that these cytoskeletal complexes are involved in recognition and interaction with extracellular matrix components.
authors.affiliation: Department of Pathology, University of South Carolina, Columbia 29208.
authors.forename: L L
authors.initials: LL
authors.lastname: Hilenski
authors.forename: L
authors.initials: L
authors.lastname: Terracio
authors.forename: T K
authors.initials: TK
authors.lastname: Borg
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D015153:Blotting, Western; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000032:analysis; D003598:Cytoskeletal Proteins / Q000032:analysis; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D005109:Extracellular Matrix / Q000502:physiology*; D016023:Integrins / Q000032:analysis; D007797:Laminin / Q000032:analysis; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000166:cytology*; D009210:Myofibrils / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D016596:Vinculin
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D016023:Integrins; D007797:Laminin; D016596:Vinculin; D003094:Collagen