Carvalho R S, Kostenuik P J, Salih E, Bumann A, Gerstenfeld L C
Department of Orthopaedic Surgery, Orthopaedic Research Laboratory, Boston University School of Medicine, 715 Albany Street, R-205, Boston, MA 02118-2526, USA.
Matrix Biol. 2003 May;22(3):241-9. doi: 10.1016/s0945-053x(03)00038-6.
Skeletal homeostasis is partly regulated by the mechanical environment and specific signals generated by a cell's adhesion to the matrix. Previous studies demonstrated that osteopontin (OPN) expression is stimulated in response to both cellular adhesion and mechanical stimulation. The present studies examine if specific integrin ligands mediate osteoblast selective adhesion and whether opn mRNA expression is induced in response to these same ligands. Embryonic chicken calvaria osteoblastic cells were plated on bacteriological dishes coated with fibronectin (FN), collagen type I (Col1), denatured collagen/gelatin (G), OPN, vitronectin (VN), laminin (LN) or albumin (BSA). Osteoblastic cells were shown to selectively adhere to FN, Col1, G and LN, yet not to VN, OPN or BSA. Opn mRNA expression was induced by adhesion to Col1, FN, LN and G, but neither OPN nor VN induced this expression. Examination of the activation of the protein kinases A and C second signaling systems showed that only adhesion to FN induced protein kinase A and protein kinase C (PKC) activity while adherence to Col1 induced PKC. Evaluation of the intracellular distribution of focal adhesion kinase (FAK) and p-tyrosine within cells after adherence to FN, VN or BSA demonstrated that adherence to FN stimulated FAK translocation from the nucleus to the cytoplasm and high levels of p-tyrosine localization at the cell surface. However, cell adherence to VN or BSA did not show these morphological changes. These data illustrate that osteoblast selective adhesion is mediated by specific integrin ligands, and induction of intracellular second signal kinase activity is related to the nature of the ligand.
骨骼稳态部分受机械环境以及细胞与基质黏附所产生的特定信号调控。先前的研究表明，骨桥蛋白（OPN）的表达会因细胞黏附和机械刺激而受到刺激。本研究旨在探讨特定整合素配体是否介导成骨细胞的选择性黏附，以及OPN mRNA表达是否会因这些相同配体而被诱导。将胚胎鸡颅盖成骨细胞接种在涂有纤连蛋白（FN）、I型胶原（Col1）、变性胶原/明胶（G）、OPN、玻连蛋白（VN）、层粘连蛋白（LN）或牛血清白蛋白（BSA）的细菌培养皿上。结果显示，成骨细胞选择性地黏附于FN、Col1、G和LN，但不黏附于VN、OPN或BSA。黏附于Col1、FN、LN和G可诱导Opn mRNA表达，但OPN和VN均未诱导这种表达。对蛋白激酶A和C第二信号系统的激活检测表明，只有黏附于FN可诱导蛋白激酶A和蛋白激酶C（PKC）活性，而黏附于Col1可诱导PKC活性。评估黏附于FN、VN或BSA后细胞内黏着斑激酶（FAK）和磷酸化酪氨酸的分布情况表明，黏附于FN可刺激FAK从细胞核向细胞质转位，并在细胞表面高水平定位磷酸化酪氨酸。然而，细胞黏附于VN或BSA并未显示出这些形态变化。这些数据表明，成骨细胞的选择性黏附由特定整合素配体介导，细胞内第二信号激酶活性的诱导与配体的性质有关。
