To test whether stretch itself directly regulates ERK-dependent h-CaD phosphorylation, we exposed human myometrial strips to in vitro stretch. Human myometrial strips were stretched to Mechanical stretch in vitro increases myometrial MedChemExpress VS-4718 contractility The above data demonstrate that the existence of stretchsensitive elements in the pregnant myometrium that result in ERK and CaD activation. Our previous work in a rat model suggested that ERK activation and subsequent CaD activation lead to corresponding changes in contractility. This hypothesis was tested in current study with term, not in labor human myometrium. As shown in figure Stretch of human myometrium induces an increase in tyrosine phosphorylation and activation of focal adhesion signaling The above data imply that gestational stretch due to the growing fetus, and, in vitro stretch imposed experimentally on the human myometrium, can induce ERK and CaD phosphorylation. Focal adhesions make direct contact with the extracellular matrix, providing a structural link between the ECM and actin cytoskeleton. FAs are mechano-sensors or transducers of ��outside-in signaling”, which is known, in non-muscle cells, to involve tyrosine phosphorylation of many 
proteins. In contrast, in differentiated, non-migrating smooth muscle cells, most signaling events regulating contractility involve Ser/Thr phosphorylation. Thus, as a first screen for adhesion plaque signaling events we probed human myometrial homogenates in the presence or absence of stretch with an anti-phosphotyrosine antibody. As is seen in Fig. October Myometrial Stretch Activation Elevations of tyrosine phosphorylation of FAK and Cas appeared to be transient in the myometrial stretch experiments. This could be explained by the dynamic assembly and disassembly of focal adhesion complexes as a function of stretch. In contrast, the downstream of resulting serine/threonine phosphorylation of ERK/CaD may integrate upstream signals and be more sustained. Probing the Identification of proteins tyrosine phosphorylated in response to myometrial stretch by SDS/PAGE and Mass Spectrometry To further identify human myometrial proteins tyrosine phosphorylated in response to stretch, we immunoprecipitated proteins with an anti-phosphotyrosine antibody using proteinmatched homogenates of unstretched and stretched myometrial strips. Fig. October Myometrial Stretch Activation myometrial tissue from pregnant women are heavily tyrosine phosphorylated in the basal state. Bands at actinin competitively displaces endogenous alphaactinin from focal adhesions, disrupts focal adhesions and reduces tyrosine phosphorylation at focal adhesions. Thus alpha-actinin plays a role in regulating stabilization of focal adhesions and its increased association with tyrosine phosphorylation could also be a contributing factor to the onset of labor. In mass spectrometric analysis of the October Myometrial Stretch Activation of h-CaD in the phosphotyrosine immunoprecipitates 8309351 may reflect the possible connection of the contractile filaments to the phosphotyrosine-containing adhesion plaques. We were unable to identify p Gestation-dependent increase in SmAV expression in both human and rat myometrial tissues Smooth muscle archvillin is an ERK regulator newly identified in our laboratory. Its presence and function in myometrial smooth muscle have not been previously studied, but it has been shown to regulate both ERK activation and contractility in vascular smooth muscle. Both