Cyclosporin G and metabolite binding to cyclophilin and a 50-kDa binding protein related to in vitro immunosuppression.

Seven purified metabolites of cyclosporin G (CsG) were studied for binding to cyclophilin and a 50-kDa binding protein (50-kDa BP). The ratios of the metabolite dissociation constants with respect to CsG were compared with in vitro immunosuppression by using the primary mixed lymphocyte suppression assay. The immunosuppressive potency ratio of the parent compounds, both cyclosporin A (CsA) and CsG, compared favorably with the drug dissociation constants for cyclophilin and the 50-kDa BP.

Development of a radioreceptor assay to measure glucocorticoids.

We have developed a radioreceptor assay to measure glucocorticoids. The assay employs the partially purified 95-kDa receptor isolated from human liver and purified by size fractionation on high-performance liquid chromatography (HPLC). In the assay [3H]prednisolone competes with steroids (endogenous and exogenous) for binding to the receptor.

cis-urocanic acid down-regulates the induction of adenosine 3',5'-cyclic monophosphate by either trans-urocanic acid or histamine in human dermal fibroblasts in vitro.

It has been demonstrated that UVB radiation (290-320 nm) suppresses mammalian cell-mediated immunity by effecting the trans to cis isomerization of urocanic acid (UCA) in the stratum corneum, the uppermost layer of the skin. Trans-urocanic acid has been shown to be the photoreceptor for UVB-induced immune suppression and the cis-isomer has been demonstrated to be immunosuppressive. Little is known, however, about how the isomerization of UCA may affect the proximal or distal cells of the skin or the immune system.

Correlation of cyclosporine and metabolite binding to cyclophilin and a 50 kDa binding protein with in vitro immunosuppression: a preliminary report.

Seven purified cyclosporine (CsA) metabolites were analyzed for binding to cyclophilin and to a 50 kDa protein purified from a JURKAT cell line. In addition, the potency of the seven metabolites, relative to CsA, was obtained using a primary mixed lymphocyte culture (MLC) suppression assay. CsA, M1, 17, and 21 were found to be immunosuppressive in the concentration range used (0-500 ng/mL).

Purification and characterization of cyclosporine and FK-506 binding proteins from a human T-helper cell line.

Cytosolic proteins that specifically bind cyclosporine A and FK-506 were isolated and purified from the JURKAT human T-helper cell line. These binding proteins were purified by affinity, molecular weight exclusion and weak cation exchange column chromatography. Radiolabeled cyclosporine A specifically bound to a approximately 17 kDa molecule which is cyclophilin and also bound to a approximately 50 kDa protein(s).