Role of Cholesterol in Formation and Function of a Signaling Complex Involving αvβ3, Integrin-Associated Protein (Cd47), and Heterotrimeric G Proteins

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Abstract
Integrin-associated protein (CD47) is a multiply membrane spanning member of the immunoglobulin superfamily that regulates some adhesion-dependent cell functions through formation of a complex with αvβ3 integrin and trimeric G proteins. Cholesterol is critical for the association of the three protein components of the supramolecular complex and for its signaling. The multiply membrane spanning domain of IAP is required for complex formation because it binds cholesterol. The supramolecular complex forms preferentially in glycosphingolipid-enriched membrane domains. Binding of mAb 10G2 to the IAP Ig domain, previously shown to be required for association with αvβ3, is affected by both the multiply membrane spanning domain and cholesterol. These data demonstrate that cholesterol is an essential component of the αvβ3/IAP/G protein signaling complex, presumably acting through an effect on IAP conformation.