| First Author | Klapproth S | Year | 2015 |
| Journal | Blood | Volume | 126 |
| Issue | 25 | Pages | 2704-12 |
| PubMed ID | 26337492 | Mgi Jnum | J:229954 |
| Mgi Id | MGI:5754932 | Doi | 10.1182/blood-2015-05-647453 |
| Citation | Klapproth S, et al. (2015) Loss of the Rap1 effector RIAM results in leukocyte adhesion deficiency due to impaired beta2 integrin function in mice. Blood 126(25):2704-12 |
| abstractText | Talin is an integrin adaptor, which controls integrin activity in all hematopoietic cells. How intracellular signals promote talin binding to the integrin tail leading to integrin activation is still poorly understood, especially in leukocytes. In vitro studies identified an integrin activation complex whose formation is initiated by the interaction of active, guanosine triphosphate (GTP)-bound Ras-related protein 1 (Rap1) with the adapter protein Rap1-GTP-interacting adapter molecule (RIAM) followed by the recruitment of talin to the plasma membrane. Unexpectedly, loss-of-function studies in mice have shown that the talin-activating role of RIAM is neither required for development nor for integrin activation in platelets. In this study, we show that leukocyte integrin activation critically depends on RIAM both in vitro and in vivo. RIAM deficiency results in a loss of beta2 integrin activation in multiple leukocyte populations, impaired leukocyte adhesion to inflamed vessels, and accumulation in the circulation. Surprisingly, however, the major leukocyte beta1 integrin family member, alpha4beta1, was only partially affected by RIAM deficiency in leukocytes. Thus, although talin is an essential, shared regulator of all integrin classes expressed by leukocytes, we report that beta2 and alpha4 integrins use different RIAM-dependent and -independent pathways to undergo activation by talin. |
