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SHARPIN is an endogenous inhibitor of β1-integrin activation
Juha K Rantala1, Jeroen Pouwels, Teijo Pellinen
1Medical Biotechnology, VTT Technical Research Centre of Finland, 20521 Turku, Finland.
None:
Regulated activation of integrins is critical for cell adhesion, motility and tissue homeostasis. Talin and kindlins activate β1-integrins, but the counteracting inhibiting mechanisms are poorly defined. We identified SHARPIN as an important inactivator of β1-integrins in an RNAi screen. SHARPIN inhibited β1-integrin functions in human cancer cells and primary leukocytes. Fibroblasts, leukocytes and keratinocytes from SHARPIN-deficient mice exhibited increased β1-integrin activity, which was fully rescued by re-expression of SHARPIN. We found that SHARPIN directly binds to a conserved cytoplasmic region of integrin α-subunits and inhibits recruitment of talin and kindlin to the integrin. Therefore, SHARPIN inhibits the critical switching of β1-integrins from inactive to active conformations.
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