Molecular Interactions of Cyclosporin A with P-glycoprotein

Abstract

The interaction between P-glycoprotein (140 -180 kDa) from the multidrug-resistant Chinese hamster ovary cell line CH R C5 and cyclosporin A was characterized using three different photoactivable cyclosporin A analogs. Two monoclonal antibodies, which are able to discriminate between two major domains of cyclosporin A (the cyclophilin and calcineurin binding domains), were used to detect the photolabeled proteins. A protein of 155 kDa corresponding to P-glycoprotein was much more strongly photolabeled in membranes of CH R C5 cells than in membranes of their drug-sensitive parent cell line AuxB1. The antitumor drug vinblastine and the reversal agents verapamil and cyclosporin A inhibited the photolabeling, and the nonimmunosuppressive derivative PSC-833 caused a stronger inhibition than cyclosporin A. P-glycoprotein photolabeled with cyclosporin A analogs was only detected with the monoclonal antibody that recognizes cyclosporin A and its metabolites, indicating that the calcineurin binding domain recognized specifically by the other antibody is not exposed. These results suggest that the portion of cyclosporin A that binds to calcineurin plays a role in the interaction of cyclosporin A with P-glycoprotein.

Cyclosporin A Traps ABCA1 at the Plasma Membrane and Inhibits ABCA1-Mediated Lipid Efflux to Apolipoprotein A-I

“…We did not investigate the mechanism by which CsA sequesters ABCA1 to the plasma membrane; however, CsA has been demonstrated to directly bind to P-gp, 37,38 and by analogy we speculate that CsA may bind directly to ABCA1 and alter its activity and cellular trafficking. Of course, other mechanisms are also possible, including calcineurin-mediated effects resulting in changes in ABCA1 phosphorylation or other post-translational modifications.…”

Stress, Drugs, and Evolution: the Role of Cellular Signaling in Fungal Drug Resistance

“…The fungal metabolites and immunosuppressants cyclosporine and FK506 bind to immunophilins, forming drug-protein complexes that are potent inhibitors of calcineurin function (109) and are synergistic with triazoles, as well as other agents mediating membrane stress responses (118,120,150). While cyclosporine and FK506 can also inhibit multidrug transporters (50,79,179,196), the specificity of their effects on calcineurin in mediating crucial responses to triazoles has been validated in C. albicans. The FK506 binding protein FKBP12, which FK506 must bind to in order to inhibit calcineurin, is required for FK506 synergy with triazoles (39), and the synergy persists even in strains lacking the multidrug transporters associated with azole resistance (119).…”

“…The fungicidal polyenes (e.g., amphotericin B) intercalate into ergosterol-containing membranes to form membrane-spanning channels that cause leakage of cellular components and, ultimately, cell death. Polyenes have been clinically exploited for over 50 years, but their utility is often compromised by toxicity to the host, likely due to the similarity between ergosterol and cholesterol in mammalian cell membranes.…”

CpABC, a Cryptosporidium parvum ATP-binding cassette protein at the host–parasite boundary in intracellular stages

“…The presence of a transporter with similar capabilities at the boundary between the parasite and host could contribute to C. parvum's drug refractory phenotype. Drugs that are effective reversers of the multidrug resistance phenotype (44), such as cyclosporin, have been shown to bind to P-glycoprotein (45). Significantly, it has been shown recently that SDZ-PSC833 and other cyclosporin analogs are potent inhibitors of intracellular growth of C. parvum (18).…”