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  • Title: Post-translational reduction of cell surface expression of insulin receptors by cyclosporin A, FK506 and rapamycin in bovine adrenal chromaffin cells.
    Author: Shiraishi S, Yokoo H, Kobayashi H, Yanagita T, Uezono Y, Minami S, Takasaki M, Wada A.
    Journal: Neurosci Lett; 2000 Nov 03; 293(3):211-5. PubMed ID: 11036198.
    Abstract:
    Long-term (>/=3 h) treatment of cultured bovine adrenal chromaffin cells with cyclosporin A (CsA) decreased cell surface (125)I-insulin binding by 62% in a concentration (IC(50)=18 microM)- and time (t(1/2)=16 h)-dependent manner, but did not change the K(d) value. FK506 (1 microM) or rapamycin (3 microM) treatment reduced (125)I-insulin binding. Western blot analysis showed that CsA treatment decreased insulin receptor (IR) beta-subunit level (t(1/2)=15 h) in membrane fraction, but did not alter total cellular levels of IR precursor and IR beta-subunit. Internalization rate of cell surface IR measured by using brefeldin A, an inhibitor of vesicular exit from the trans-Golgi network, was comparable between non-treated and CsA-treated cells. Thus, CsA, FK506 and rapamycin inhibit peptidyl prolyl cis-trans isomerase activities of cyclophilin and FK506-binding protein, and down-regulate IR presumably by reducing cell surface externalization of IR.
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