title: Tensile stress induces alpha-adaptin C production in mouse calvariae in an organ culture: possible involvement of endocytosis in mechanical stress-stimulated osteoblast differentiation.
abstract: We previously demonstrated that tensile stress (TS)-induced osteoblast differentiation eventually led to osteogenesis in an organ culture of mouse calvarial sutures. In the present study, we employed RNA-fingerprinting using an arbitrarily primed polymerase chain reaction (RAP-PCR) to identify alpha-adaptin C, a component of the endocytosis machinery AP2, as a TS-inducible gene. Protein production, as well as the gene expression of alpha-adaptin C, was induced by TS as early as 3 h following the initiation of loading. In situ hybridization and immunohistochemical analysis revealed that the induction of alpha-adaptin C mostly occurred in fibroblastic cells in the sutures, suggesting that it precedes TS-induced osteoblast differentiation. Consistent with this result, TS significantly increased the number of coated pits (CPs) and coated vesicles (CVs) in the undifferentiated fibroblastic cells but not in the osteoblastic cells around calvarial bones. Further, TS-induced osteoblast differentiation was suppressed when endocytosis was inhibited by potassium depletion. These results, taken together, suggest that TS accelerates osteoblast differentiation and osteogenesis, possibly through the induction of the alpha-adaptin C expression and consequent activation of receptor-mediated endocytosis.
authors.affiliation: Division of Cell Biology and Molecular Pharmacology, Niigata University Graduate School of Medical and Dental Sciences, Gakkocho-dori, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Shimomura
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishibashi
authors.forename: Mika
authors.initials: M
authors.lastname: Ikegame
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yoshizawa
authors.forename: Sadakazu
authors.initials: S
authors.lastname: Ejiri
authors.forename: Tadashi
authors.initials: T
authors.lastname: Noda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawashima
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D033965:Adaptor Protein Complex alpha Subunits / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation; D003034:Coated Pits, Cell-Membrane / Q000648:ultrastructure; D018699:Coated Vesicles / Q000648:ultrastructure; D003393:Cranial Sutures / Q000033:anatomy & histology / Q000378:metabolism / Q000648:ultrastructure; D004705:Endocytosis; D005786:Gene Expression Regulation; D051379:Mice; D009924:Organ Culture Techniques; D010006:Osteoblasts / Q000166:cytology*; D010012:Osteogenesis; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D012886:Skull / Q000166:cytology; D013314:Stress, Mechanical
chemical_list: D033962:Adaptor Protein Complex 2; D033965:Adaptor Protein Complex alpha Subunits; D012333:RNA, Messenger; C439124:adaptor protein complex 2, alpha 2 subunit