title: The expression of alpha 2 beta 1 integrin and alpha smooth muscle actin in fibroblasts grown on collagen.
abstract: The maturation of connective tissue involves the organization of collagen fibres by resident fibroblasts. Fibroblast attachment to collagen has been demonstrated to involve cell surface receptors, integrins of the beta 1 family. Integrins are associated with cytoplasmic actin of microfilaments either directly or through focal adhesions. The major actin isoform of fibroblast microfilaments is beta actin and to a lesser extent alpha smooth muscle (alpha SM) actin. Cultured human dermal fibroblasts derived from adult dermis, newborn foreskin or keloid scar were grown on either uncoated or collagen-coated surfaces. The expression and synthesis of both alpha 2 beta 1 integrin and alpha SM actin were followed by immunohistology and immunoprecipitation. Fibroblasts on uncoated surfaces expressed little alpha 2 beta 1 integrin on their surface, while 20 per cent of them demonstrated alpha SM actin within microfilaments. Fibroblasts grown on a collagen-coated surface minimally expressed alpha SM actin in microfilament structures and a majority of the cells were positive for alpha 2 beta 1 integrin on their membranes. Using [35S]-methionine incorporation and immunoprecipitation, it was shown that fibroblasts grown in uncoated dishes synthesized more alpha SM actin than fibroblasts grown on collagen-coated dishes. In contrast, fibroblasts grown on collagen coated dishes synthesized more alpha 2 beta 1 integrin compared to the same cells grown on uncoated dishes. Fibroblasts maintained on a type I collagen upregulate the expression and synthesis of alpha 2 beta 1 integrin, and downregulate the expression and synthesis of alpha SM actin.
authors.affiliation: Division of Pediatric Surgery, Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033, USA.
authors.forename: H P
authors.initials: HP
authors.lastname: Ehrlich
authors.forename: O
authors.initials: O
authors.lastname: Cremona
authors.forename: G
authors.initials: G
authors.lastname: Gabbiani
mesh_terms: D000199:Actins / Q000096:biosynthesis*; D000328:Adult; D002478:Cells, Cultured; D003094:Collagen / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D016023:Integrins / Q000096:biosynthesis*; D007627:Keloid / Q000378:metabolism; D008297:Male; D011233:Precipitin Tests
chemical_list: D000199:Actins; D016023:Integrins; D003094:Collagen