Mechanosensitive tyrosine phosphorylation of paxillin and focal adhesion kinase in tracheal smooth muscle

focal adhesion kinase in tracheal smooth muscle. Am. J. Physiol. 276 (Cell Physiol. 45): C250–C258, 1999.—We inves-tigated the role of the integrin-associated proteins focal adhesion kinase (FAK) and paxillin as mediators of mechano-sensitive signal transduction in tracheal smooth muscle. In muscle strips contracted isometrically with ACh, we observed higher levels of tyrosine phosphorylation of FAK and paxillin at the optimal muscle length (Lo) than at shorter muscle lengths of 0.5 or 0.75 Lo. Paxillin phosphorylation was also length sensitive in muscles activated by K1 depolarization and adjusted rapidly to changes in muscle length imposed after contractile activation by either ACh or K1 depolariza-tion. Ca21 depletion did not affect the length sensitivity of paxillin and FAK phosphorylation in muscles activated with ACh, indicating that the mechanotransduction process can b