Localized zones of Rho and Rac activities drive initiatioon and expansion of epithelial cell-cell adhesion (J Cell Biol, 2007, 178:517-527)

報告日期: 2007/11/27
報告時間: 17:10/18:00
報告學生: 張玲華
講評老師: 謝清河


Localized zones of Rho and Rac activities drive initiation and expansion of epithelial cell-cell adhesion

J. Cell Biol. 178: 517-527(2007)


Speaker: Ling-Hua Chang

Commentator: Patrick C.H. Hsieh, M.D., Ph.D.)

Place: Room602

Date: 2007/11/27 17:00-18:00



Cadherin-madiated cell-cell adhesion plays important roles in determining cell shape, movement, and sorting. Using high-resolution live-cell imaging, biosensors, and small molecular inhibitors to show for the first time the distribution of active Rac1 and its downstream effectors the Arp2/3 complex and lamellipodia and active RhoA and its downstream effectors phosphomyosin II actomyosin contraction during de novo contacts between epithelial cells. When initial adhesion result in the rapid accumulation of E-cadhesion. But actin filaments do not bind directly to the cadherin-cadherin complex. And the second stage of cell-cell adhesion involves active expansion of the contact that required E-cadherin and an active process requiring localized actomyosin activation and contractility. Predicted zones of E-cadherin accumulation, Rac1-induced lamellipodia protrusions, and RhoA-induced actomyosin contraction coordinately induce and expand the cell-cell contact. Because integrin- mediated adhesion also regulates cadherin function. To verify what kinds of adhesion pathway activates RhoA, author use TIRF-M in live cells to detect adhesion to the substratum at the contact edges indicates that E-cadherin and integrin-mediated adherin sites are in very close spatial proximity to each other. Besides, cortical actin bundles seem to be closely associated with both of them. But E-cadhesion-catenin complex does not bind actin directly, which indicates that at these sites actin may be anchored by integrin-based focal adhesion. Further studies on actin linkage to integrins and cross talk with the E-cadherin-catenin complex are required to resolve the mechanisms.    



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