Abstract
When exposed to uniaxial cyclic stretch (20%, 1 Hz), cultured human umbilical endothelial cells (HUVECs) gradually change their morphology to complete a spindle-like shape with the major axis perpendicular to the stretch axis within 2hrs. Associated with this response, the level of tyrosine phosphorylation of focal proteins is increased. However, changes in the distribution of tyrosine phosphorylated proteins during stretch, which may relate to the directional shape change, are not known. In this study we measured time-dependent changes in the distribution of tyrosine-phosphorylated focal proteins during uniaxial cyclic stretch. Tyrosine phosphorylated proteins were labeled with fluorescent dye -conjugated PY-20, an antibody against phosphorylated tyrosine. Focal contacts (FCs) of unstretched cells were uniformly stained with PY-20, however, the staining declined in all FCs 2 min after the onset of stretch. Ten min after the stretch, higher level of PY-20 staining was observed at the extending cell edges perpendicular to the stretch axis. These results suggest that uniaxial cyclic stretch induced a transient and global tyrosine dephosphorylation of focal proteins, then caused an stretch-axis dependent tyrosine-phosphorylation of focal proteins. Such a spatially regulated tyrosine phosphorylation may contribute to the directional shape change caused by uniaxial cyclic stretch. [Jpn J Physiol 55 Suppl:S81 (2005)]
