CD81 is essential for the formation of membrane protrusions and regulates Rac1-activation in adhesion-dependent immune cell migration

Speaker: Ming-Zhang Lin (林明璋)                              Time: 15:10~16:00, Dec. 3, 2011

Commentator: Dr. Bei-Chang Yang (楊倍昌老師)      Place: Room 601

Abstract:

        CD81 (TAPA-1) is a member of the tetraspanin family, has its ability to recruit signaling enzymes such as protein kinase C which can phosphorylate integrin and participates in several signal transduction cascades. By clustering with many surface proteins including beta1-integrins, CD81 could regulate actin cytoskeleton organization and cell migration. In CD81-/- mice, sperm-egg fusion is reduced during oocyte fertilization, and antibody-mediated immune responses are significantly delayed. Rac1 is a small G-protein in the Rho family that drives actin polymerization and formation of lamellipodia it could regulate cell migration. Previous studies have pointed out that tetraspanin is responsible for cell motility, but its role in immune cell migration is still unknown. In this article, the authors investigate the effect of CD81 on membrane protrusion formation and Rac-1 activation in immune cell migration. CD81 is not required for the maturation of DCs and regulated formation of membrane protrusion in DCs which is via activation of Rac-1. By using total internal reflection fluorescence microscopy, they demonstrated that CD81 neither regulated beta 1-integrin affinity nor avidity. However, CD 81 organized adhesion structures at the leading edge of protruding lamellipodia on 2D surfaces. In contrast, CD81 is not required for DCs mobility in 3D tissues like environments. Collectively, this study found that CD81 is an important regulator of immune cellchemotaxis and formation of membrane protrusion on 2D surface but not in 3D collagen gel.

References:

1.      Zhang, X. A.,et al. Transmembrane- 4 superfamily proteins associate with activated protein kinase C and link PKC to specific beta-1integrins. 2001.  J Biol Chem. 276(27): 25005-25013.

2.      Krämer, B.,et al. Regulation of NK cell trafficking by CD81. 2009.  Eur J Immunol. 39(12): 3447-3458.