Cardenas M E, Hemenway C, Muir R S, Ye R, Fiorentino D, Heitman J
Department of Genetics, Duke University Medical Center, Durham, NC 27710.
EMBO J. 1994 Dec 15;13(24):5944-57. doi: 10.1002/j.1460-2075.1994.tb06940.x.
The peptidyl-prolyl isomerases FKBP12 and cyclophilin A (immunophilins) form complexes with the immunosuppressants FK506 and cyclosporin A that inhibit the phosphatase calcineurin. With the yeast two hybrid system, we detect complexes between FKBP12 and the calcineurin A catalytic subunit in both the presence and absence of FK506. Mutations in FKBP12 surface residues or the absence of the calcineurin B regulatory subunit perturb the FK506-dependent, but not the ligand-independent, FKBP12-calcineurin complex. By affinity chromatography, both FKBP12 and cyclophilin A bind calcineurin A in the absence of ligand, and FK506 and cyclosporin A respectively potentiate these interactions. Both in vivo and in vitro, the peptidyl-prolyl isomerase active sites are dispensable for ligand-independent immunophilin-calcineurin complexes. Lastly, by genetic analyses we demonstrate that FKBP12 modulates calcineurin functions in vivo. These findings reveal that immunophilins interact with calcineurin in the absence of exogenous ligands and suggest that immunosuppressants may take advantage of the inherent ability of immunophilins to interact with calcineurin.
肽基脯氨酰异构酶FKBP12和亲环蛋白A（免疫亲和素）与免疫抑制剂FK506和环孢素A形成复合物，这些复合物可抑制磷酸酶钙调神经磷酸酶。利用酵母双杂交系统，我们在存在和不存在FK506的情况下均检测到FKBP12与钙调神经磷酸酶A催化亚基之间的复合物。FKBP12表面残基的突变或钙调神经磷酸酶B调节亚基的缺失会干扰FK506依赖性的FKBP12 - 钙调神经磷酸酶复合物，但不影响非配体依赖性的复合物。通过亲和层析，在没有配体的情况下，FKBP12和亲环蛋白A均可结合钙调神经磷酸酶A，FK506和环孢素A分别增强了这些相互作用。在体内和体外，肽基脯氨酰异构酶活性位点对于非配体依赖性的免疫亲和素 - 钙调神经磷酸酶复合物都是可有可无的。最后，通过遗传学分析，我们证明FKBP12在体内调节钙调神经磷酸酶的功能。这些发现揭示了免疫亲和素在没有外源性配体的情况下与钙调神经磷酸酶相互作用，并表明免疫抑制剂可能利用了免疫亲和素与钙调神经磷酸酶相互作用的固有能力。
