The cytosolic protein talin induces an intermediate affinity integrin alphaLbeta2.
The integrin alphaLbeta2 mediates leukocyte adhesion and migration that are required for a functional immune system. It is known that inside-out signaling triggers alphaLbeta2 conformational changes, which affect its ligand-binding affinity. At least three alphaLbeta2 affinity states (low, intermediate, and high) were described. The cytosolic protein talin connects alphaLbeta2 to the actin filament. The talin head domain is also known to activate alphaLbeta2 ligand binding. However, it remains to be determined whether talin promotes an intermediate or high affinity alphaLbeta2. In this study using transfectants and T cells, we showed that talin induced an intermediate affinity alphaLbeta2 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 alphaLbeta2 induced by talin allowed adhesion and migration of T cells on immobilized ICAMs.
Li
Yan-Feng
YF
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
Tang
Ren-Hong
RH
Puan
Kia-Joo
KJ
Law
S K Alex
SK
Tan
Suet-Mien
SM
D015703:Antigens, CD / Q000378:metabolism; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D013601:T-Lymphocytes / Q000737:chemistry* / Q000166:cytology; D016608:Talin / Q000378:metabolism*; D014162:Transfection
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; C065289:ICAM2 protein, human; C483616:ICAM3 protein, human; D016169:Lymphocyte Function-Associated Antigen-1; D016608:Talin; D018799:Intercellular Adhesion Molecule-1