Use this URL to cite or link to this record in EThOS:
Title: Integrin-mediated mechanotransduction in human articular chondrocytes
Author: Lee, Herng-Sheng
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
Mechanical forces influence chondrocyte metabolism and function. It has been shown that 0.33 Hz cyclical mechanical stimulation results in membrane hyperpolarization of normal human articular chondrocytes by activation of Ca2+ -dependent K+ (SK) channels. Using pharmacological inhibitors of intracellular signalling molecules, stretch-activated ion channels (SAC) and specific antibodies against integrins, integrin-associated protein, cytokines and cytokine receptors the data show that membrane hyperpolarization is the result of mechanically-induced secretion of IL-4. Secreted IL-4 binds to type II IL-4 receptors and stimulates a signal cascade involving PLC and PKC leading to activation of SK channels. Specific blockade of a5b1 integrins, SAC and tyrosine kinases block mechanically-induced membrane hyperpolarization but have no effect on the hyperpolarization of exogenously added IL-4 consistent with a role for these molecules upstream of IL-4 release in the mechanotransduction pathway. Studies of OA chondrocytes demonstrate that unlike normal chondrocytes, these cells show a membrane depolarization response to 0.33 Hz mechanical stimulation as a result of activation of tetrodotoxin-sensitive Na+ channels. The mechanotransduction pathway involves a5b1 integrins, SAC, tyrosine kinases, PLC, PI 3-kinase and cytokines secretion but the actin cytoskeleton and PKC, which are important in the membrane hyperpolarization response in normal chondrocytes, are not necessary for membrane depolarization in OA chondrocytes following mechanical stimulation. The tyrosine phosphorylation events in the mechanotransduction pathway have been investigated in detail. The results show tyrosine phosphorylation of three major proteins, p125, p90, and p70 within 1 min of onset of mechanical stimulation. Immunoblotting and immunoprecipitation show these to be FAK, b-catenin, and paxillin, respectively. Tyrosine phosphorylation of all three proteins is inhibited by RGD containing oligopeptides and gadolinium, which is known to block SAC. b-catenin coimmunoprecipitates with FAK and is colocalized with a5 integrin and FAK. These results indicate a previously unrecognized role for an integrin-b-catenin signalling pathway in human articular chondrocyte responses to mechanical stimulation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available