Identification of p125 as FAK and p130 as Cas.
A. Stretch selectively activates FAK at tyrosine site 925, not site 397. Term pregnant uterine smooth muscle strips were unstretched or stretched to 2x slack length at indicated time period. The tissue homogenates were probed with FAK site-specific antibodies. Phospho-FAK signals are normalized to the total FAK protein or alpha-Tubulin. *p<0.05 compared to unstretched control samples (by ANOVA). n = 3–5 in each group. Typical blots were shown on the top. Both FAK total protein antibody and FAK-Y925 phospho antibody are rabbit polyclonal antibodies, thus, a-tubulin mouse monoclonal antibody was chosen for normalization of the FAK-Y925 signal. B. Stretch activates pCas130. Phospho-Cas signals are normalized to Cas protein levels and expressed as p-Cas/Cas ratios. *p<0.05 compared to unstretched control samples (by ANOVA). n = 3–5 samples in each group.