| Research Abstract |
Endothelial cells exhibit spindle like shape aligning their longitude parallel with vessel running. This peculiar shape and alignment is significant 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 periodic circumferential stretch by pulsative blood flow, is enough to induce such a morphology of 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 intracellular signaling cascade in the stretch induced morphogenesis in cultured endothelial cells and to understand the molecular mechanism underlying the formation of two dimensional polarity in the cell. Using Ca ィイD12+ィエD1 imaging, patch clamp, biochemical and molecular biological techniques, we could identify the major signaling cascade as follows : < uniaxial periodic stretch
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→ activation of SA channels→ intracellular Ca-mobilization→activation of tyrosine kinase, src,→tyrosine phosphorylation of adhesion proteins→ reorganization of stress fibers and forcal adhesion→ morphological change>. In the present study, we focused on the origin of the cell polarity and obtained following results. : 1) As the stretch activated intracellular CaィイD12+ィエD1 increase was spatially uniform, this may not be true cause of the cell polarity. 2) Stretch dependent cAMP increase may not directly relate to the morphological change. 3) On the other hand, stress fibres tend to align perpendiculary to the stretch axis prior to the morphological change. 4) Therefore, there may be another signaling mechanism flowing from the integrin, upon which mechanical forces are directly imposed, to cytoskeletons. 5) To investigate the role of the integrin, we developed a near field microscope system by which we can visualize the dynamics of integrin molecules in real time. 6) Integrin molecules were found to be translocated rapidly than we expected. We speculate that the signaling mechanism via integrins along with the CaィイD12+ィエD1 signaling mechanism may contribute to the formation of the cell polarity. Next aim of our study should be to prove this hypothesis. Less
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