Integrin and mechanosensitive ion channel-dependent tyrosine phosphorylation of focal adhesion proteins and beta-catenin in human articular chondrocytes after mechanical stimulation.
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 Ca(2+)-dependent K+ small conductance potassium activated calcium (SK) channels. The mechanotransduction pathway involves alpha 5 beta 1-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), beta-catenin, and paxillin, respectively. Tyrosine phosphorylation of all three proteins is inhibited by RGD containing oligopeptides and gadolinium, which is known to block SAC. beta-catenin coimmunoprecipitates with FAK and is colocalized with alpha 5-integrin and pp125FAK. These results indicate a previously unrecognized role for an integrin-beta-catenin signaling pathway in human articular chondrocyte (HAC) responses to mechanical stimulation.
Department of Pathology, Edinburgh University Medical School, U.K.
H S
HS
Lee
S J
SJ
Millward-Sadler
M O
MO
Wright
G
G
Nuki
D M
DM
Salter
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000378:metabolism; D002358:Cartilage, Articular / Q000166:cytology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005260:Female; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D039482:Integrin alpha5; D016023:Integrins / Q000378:metabolism*; D007719:Knee Joint / Q000166:cytology; D008297:Male; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051640:Small-Conductance Calcium-Activated Potassium Channels; D013314:Stress, Mechanical; D015534:Trans-Activators; D014443:Tyrosine / Q000378:metabolism*; D051176:beta Catenin
D015703:Antigens, CD; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D039482:Integrin alpha5; D016023:Integrins; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D015534:Trans-Activators; D051176:beta Catenin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human