Cyclosporine (CsA) binds to which type of proteins?

Cyclosporine (CsA) primarily binds to immunophilins, specifically cyclophilin. This interaction is significant because it is through the binding to cyclophilin that CsA exerts its immunosuppressive effects. When CsA binds to immunophilins, it forms a complex that inhibits the activity of calcineurin, a protein phosphatase that is crucial in the activation of T-cells. This mechanism of action is fundamental in preventing organ rejection in transplant recipients and managing autoimmune diseases.

In contrast, while serum albumins may bind various drugs to influence their distribution and bioavailability, this is not the primary mechanism through which CsA functions. Drug transporters are involved in the absorption, distribution, and elimination of many drugs but are not directly linked to CsA's specific mechanism of immunosuppression. Cytokine receptors are part of signaling pathways involved in immune responses, but CsA does not bind to these receptors to exert its effects. Thus, the interaction between CsA and immunophilins is the central aspect of its biochemical role in immunopharmacology.