The Cytosolic Protein Talin Induces an Intermediate Affinity Integrin αLβ2

• Published in: The Journal of biological chemistry Vol. 282; no. 33; p. 24310
• Main Authors: Yan-Feng Li, Ren-Hong Tang, Kia-Joo Puan, S. K. Alex Law, Suet-Mien Tan
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 17.08.2007
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M701860200

The integrin α L β 2 mediates leukocyte adhesion and migration that are required for a functional immune system. It is known that inside-out signaling triggers α L β 2 conformational changes, which affect its ligand-binding affinity. At least three α L β 2 affinity states (low, intermediate, and high) were described. The cytosolic protein talin connects α L β 2 to the actin filament. The talin head domain is also known to activate α L β 2 ligand binding. However, it remains to be determined whether talin promotes an intermediate or high affinity α L β 2 . In this study using transfectants and T cells, we showed that talin induced an intermediate affinity α L β 2 that adhered constitutively to its ligand intercellular adhesion molecule (ICAM)-1 but not ICAM-3. Adhesion to ICAM-3 was induced when an additional exogenous activating agent was included. Similar profiles were observed with soluble ICAMs. In addition, the intermediate affinity α L β 2 induced by talin allowed adhesion and migration of T cells on immobilized ICAMs.