AF6 negatively regulates Rap1-induced cell adhesion

J Biol Chem. 2005 Sep 30;280(39):33200-5. doi: 10.1074/jbc.M505057200. Epub 2005 Jul 28.

Abstract

AF6 is involved in the connection of membrane-associated proteins to the actin cytoskeleton. It binds to Ras-like small GTPases and is suggested to be an effector of both Ras and Rap. Here we show that knockdown of AF6 in T cells by RNA interference enhanced Rap1-induced integrin-mediated cell adhesion, whereas overexpression of AF6 had the opposite effect. Interestingly, AF6-induced inhibition of cell adhesion correlated with an increase in RapGTP levels. Like AF6, protein KIAA1849 contains a Ras association domain and interacted with Rap1. However, KIAA1849 did not inhibit Rap1-induced cell adhesion. We concluded that AF6 is a negative regulator of Rap-induced cell adhesion. We proposed that AF6 inhibits Rap-mediated cell adhesion by sequestering RapGTP in an unproductive complex and thus prevents the interaction of Rap1 not only with effectors that mediate adhesion but also with Rap GTPase-activating proteins. Thus, AF6 may buffer RapGTP in resting T cells and maintain them in a non-adherent state.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cell Adhesion
  • Gene Expression Regulation*
  • Glutathione Transferase / metabolism
  • Humans
  • Integrins / metabolism
  • Jurkat Cells
  • Kinesin / metabolism*
  • Myosins / metabolism*
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Retroviridae / genetics
  • rap1 GTP-Binding Proteins / metabolism*

Substances

  • AFDN protein, human
  • Integrins
  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • Glutathione Transferase
  • Myosins
  • Kinesin
  • rap1 GTP-Binding Proteins