STRETCH-INDUCED CELL MORPHOGENEISI : MOLECULAR MECHANISM OF DIRECTIONSENSITIVITY AND POLARITY FORMATION

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Endothelial cells exhibit spindle like shape aligning their longtude parallel with vessel running. This peculiar shape and alignment is isgnificant to prevent the cells from being pealed off by blood flow. However, cultured endothelial cells do not show such a shape and alignment, It is known that mechanical stresses onto the cells, like shear stress and periodic circumferential stretch, by pulsative blood flow are enough to induce such a morphology in endothelial cells. It has been also suggested that cytoskeletons and adhesion molecules contribute to this morphogenesis. The altimate goal of this project is to elucidate the signaling cascade in the stretchOinduced morphogenesis in cultured endothelial cells and to understand the molecular mechanism underlying the formation of two dimensional polarity in the cell. Using Ca^<2+>imaging, patch clamp, biochemical and molecular biological techniques, we could identify the major signaling cascade in the stretch-induced morphogenesis as follows : <uniaxial periodic stretch* activation of SA channels* intracellular C_amobilization* activation of calcinyrin* activation of tyrosine kinase, src, * tyrosine phosphorylation of adhesion proteins* reorganization of stress fibers and forcal adhesion* morphological change>. However, as the stretch activated Ca^<2+> increase was spatially uniform, this may not be the cause of the cell polarity. On the other hand, tyrosine phosphorylated proteins favored to distribute at the elongating portion of the cell. Hence, it is possible that there is another signaling mechanism flowing from adhesion plaque (integrin), upon which mechanical forces are directly imposed, to intracellular space. This mechanism may along with the former signaling mechanism contribute to the formation of the cell polarity through the regulation of tyrosine phosphorylation of focal adhesion proteins. Next step of our project should be to prove this hypothesis.