Price E R, Jin M, Lim D, Pati S, Walsh C T, McKeon F D
Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):3931-5. doi: 10.1073/pnas.91.9.3931.
Cyclophilin B is targeted to the secretory pathway via an endoplasmic reticulum signal sequence. We analyzed the localization and trafficking of endogenous and transfected cyclophilin B in mammalian cells. Cyclophilin B accumulates both in the endoplasmic reticulum and in complexes on the plasma membrane. The immunosuppressant cyclosporin A specifically mobilizes cyclophilin B from the endoplasmic reticulum, and promotes the secretion of cyclophilin B into the medium. We suggest that cyclosporin A competes with endogenous plasma membrane proteins for association with cyclophilin B in the secretory pathway. These findings argue in favor of a role for cyclophilin B as a chaperone to proteins destined for the plasma membrane, rather than solely as a proline isomerase functioning within the endoplasmic reticulum.
亲环素B通过内质网信号序列靶向分泌途径。我们分析了哺乳动物细胞中内源性和转染的亲环素B的定位和运输。亲环素B在内质网和质膜上的复合物中均有积累。免疫抑制剂环孢菌素A特异性地将亲环素B从内质网中动员出来，并促进亲环素B分泌到培养基中。我们认为环孢菌素A在分泌途径中与内源性质膜蛋白竞争与亲环素B的结合。这些发现支持亲环素B作为运往质膜的蛋白质的伴侣的作用，而不仅仅是作为在内质网中起作用的脯氨酸异构酶。
