Integrin and Mechanosensitive Ion Channel‐Dependent Tyrosine Phosphorylation of Focal Adhesion Proteins and β‐Catenin in Human Articular Chondrocytes After Mechanical Stimulation

• Published in: Journal of bone and mineral research Vol. 15; no. 8; pp. 1501 - 1509
• Main Authors: Lee, H. S., Millward‐Sadler, S. J., Wright, M. O., Nuki, G., Salter, D. M.
• Format: Journal Article
• Language: English
• Published: Washington, DC John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR) 01-08-2000; American Society for Bone and Mineral Research
• Subjects: Aged; Aged, 80 and over; Antigens, CD - metabolism; b-Catenin; beta Catenin; Biological and medical sciences; Cartilage, Articular - cytology; Cells, Cultured; chondrocyte; Chondrocytes - cytology; Cytoskeletal Proteins - metabolism; Female; focal adhesion kinase; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Fundamental and applied biological sciences. Psychology; Humans; integrin; Integrin alpha5; Integrins - metabolism; Knee Joint - cytology; Male; mechanotransduction; paxillin; Phosphorylation; phosphotyrosine; Potassium Channels - metabolism; Potassium Channels, Calcium-Activated; Precipitin Tests; Protein-Tyrosine Kinases - metabolism; Skeleton and joints; Small-Conductance Calcium-Activated Potassium Channels; Stress, Mechanical; Trans-Activators; Tyrosine - metabolism; tyrosine phosphorylation; Vertebrates: osteoarticular system, musculoskeletal system; β‐catenin; Osteoarticular system; Human; Tyrosine; Signal transduction; Phosphorylation; Beta stereoisomer; Integrin; Articular cartilage; Chondrocyte; Ionic channel; Mechanical stimulus; Catenin
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.2000.15.8.1501

Mechanical forces influence chondrocyte metabolism and function. We have previously shown that 0.33 Hz cyclical pressure‐induced strain (PIS) results in membrane hyperpolarization of normal human articular chondrocytes (HAC) by activation of Ca2+‐dependent K+ small conductance potassium activated calcium (SK) channels. The mechanotransduction pathway involves α5β1‐integrin, stretch‐activated ion channels (SAC) actin cytoskeleton and tyrosine protein kinases, with subsequent release of the chondroprotective cytokine interleukin‐4 (IL‐4). The objective of this study was to examine in detail tyrosine phosphorylation events in the mechanotransduction pathway. The results show tyrosine phosphorylation of three major proteins, p125, p90, and p70 within 1 minute of onset of mechanical stimulation. Immunoblotting and immunoprecipitation show these to be focal adhesion kinase (pp125FAK), β‐catenin, and paxillin, respectively. Tyrosine phosphorylation of all three proteins is inhibited by RGD containing oligopeptides and gadolinium, which is known to block SAC. β‐catenin coimmunoprecipitates with FAK and is colocalized with α5‐integrin and pp125FAK. These results indicate a previously unrecognized role for an integrin‐β‐catenin signaling pathway in human articular chondrocyte (HAC) responses to mechanical stimulation.