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
附件下載:

http://basicmed.med.ncku.edu.tw/upload_data/961127-3.pdf

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

 

Abstract:

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.    

 

Referance:

1.     Hall A. et al., Rho GTPases in cell biology. Nature. 420:629-635 (2002)

2.     Nelson W. J. et al., Effects of Regulated Expression of Mutant RhoA and Rac1 Small GTPases on the Development of Epithelial (MDCK) Cell Polarity. J. Cell Biol. 142: 85–100 (1998)