Dumont F J, Staruch M J, Koprak S L, Siekierka J J, Lin C S, Harrison R, Sewell T, Kindt V M, Beattie T R, Wyvratt M
Department of Immunology, Merck Research Laboratories, Rahway, New Jersey 07065.
J Exp Med. 1992 Sep 1;176(3):751-60. doi: 10.1084/jem.176.3.751.
FK-506 inhibits Ca(2+)-dependent transcription of lymphokine genes in T cells, and thereby acts as a powerful immunosuppressant. However, its potential therapeutic applications may be seriously limited by several side effects, including nephrotoxicity and neurotoxicity. At present, it is unclear whether these immunosuppressive and toxic effects result from interference with related biochemical processes. FK-506 is known to interact with FK-binding protein-12 (FKBP-12), an abundant cytosolic protein with cis-trans peptidyl-prolyl isomerase activity (PPIase) activity. Because rapamycin (RAP) similarly binds to FKBP-12, although it acts in a manner different from FK-506, by inhibiting T cell responses to lymphokines, such an interaction with FKBP-12 is not sufficient to mediate immunosuppression. Recently, it was found that the complex of FKBP-12 with FK-506, but not with RAP, inhibits the phosphatase activity of calcineurin. Here, we used L-685,818, the C18-hydroxy, C21-ethyl derivative of FK-506, to explore further the role of FKBP-12 in the immunosuppressive and toxic actions of FK-506. Although L-685,818 bound with high affinity to FKBP-12 and inhibited its PPIase activity, it did not suppress T cell activation, and, when complexed with FKBP-12, did not affect calcineurin phosphatase activity. However, L-685,818 was a potent antagonist of the immunosuppressive activity of both FK-506 and RAP. Moreover, L-685,818 did not induce any toxicity in dogs and rats or in a mouse model of acute FK-506 nephrotoxicity, but it blocked the effect of FK-506 in this model. Therefore, FK-506 toxicity involves the disruption of biochemical mechanisms related to those implicated in T cell activation. Like immunosuppression, this toxicity is not due to the inhibition of the PPIase activity of FKBP-12, but may be linked to the inhibition of the phosphatase activity of calcineurin by the drug FKBP-12 complex.
FK-506抑制T细胞中淋巴因子基因的钙依赖性转录，从而作为一种强效免疫抑制剂发挥作用。然而，其潜在的治疗应用可能会受到包括肾毒性和神经毒性在内的几种副作用的严重限制。目前，尚不清楚这些免疫抑制和毒性作用是否源于对相关生化过程的干扰。已知FK-506与FK结合蛋白-12（FKBP-12）相互作用，FKBP-12是一种丰富的胞质蛋白，具有顺反肽基脯氨酰异构酶活性（PPIase）。因为雷帕霉素（RAP）同样与FKBP-12结合，尽管其作用方式与FK-506不同，通过抑制T细胞对淋巴因子的反应，但这种与FKBP-12的相互作用不足以介导免疫抑制。最近发现，FKBP-12与FK-506而非与RAP形成的复合物抑制钙调神经磷酸酶的磷酸酶活性。在此，我们使用L-685,818（FK-506的C18-羟基、C21-乙基衍生物）来进一步探究FKBP-12在FK-506免疫抑制和毒性作用中的作用。尽管L-685,818与FKBP-12具有高亲和力结合并抑制其PPIase活性，但它并未抑制T细胞活化，并且与FKBP-12复合时也不影响钙调神经磷酸酶的磷酸酶活性。然而，L-685,818是FK-506和RAP免疫抑制活性的强效拮抗剂。此外，L-685,818在犬、大鼠或急性FK-506肾毒性小鼠模型中未诱导任何毒性，但它在该模型中阻断了FK-506的作用。因此，FK-506毒性涉及与T细胞活化相关的生化机制的破坏。与免疫抑制一样，这种毒性并非由于FKBP-12的PPIase活性受到抑制，而是可能与药物FKBP-12复合物对钙调神经磷酸酶磷酸酶活性的抑制有关。
