Institute of Molecular Medicine, College of Medicine, National Taiwan University and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan.
J Cell Sci. 2012 Oct 1;125(Pt 19):4586-96. doi: 10.1242/jcs.107797. Epub 2012 Jul 5.
Golgins play diverse roles in regulating the structure and function of the Golgi. The yeast golgin Imh1p is targeted to the trans-Golgi network (TGN) through interaction of its GRIP domain with GTP-bound Arl1p. Recycling of Arl1p and Imh1p to the cytosol requires the hydrolysis of GTP bound to Arl1p; however, the point at which GTP hydrolysis occurs remains unknown. Here, we report that self-interaction of Imh1p plays a role in modulating spatial inactivation of Arl1p. Deletion of IMH1 in yeast decreases the amount of the GTP-bound Arl1p and results in less Arl1p residing on the TGN. Biochemically, purified Imh1p competes with Gcs1p, an Arl1p GTPase-activating protein (GAP), for binding to Arl1p, thus interfering with the GAP activity of Gcs1p toward Arl1p. Furthermore, we demonstrate that the self-interaction of Imh1p attenuates the Gcs1p-dependent GTP hydrolysis of Arl1p. Thus, we propose that the golgin Imh1p serves as a feedback regulator to modulate the GTP hydrolysis of Arl1p.
高尔基复合体蛋白在调节高尔基体的结构和功能方面发挥着多种作用。酵母高尔基糖蛋白 Imh1p 通过其 GRIP 结构域与 GTP 结合的 Arl1p 相互作用，靶向到反式高尔基体网络（TGN）。Arl1p 和 Imh1p 循环回细胞质需要 GTP 结合的 Arl1p 水解；然而，GTP 水解发生的点仍然未知。在这里，我们报告说 Imh1p 的自我相互作用在调节 Arl1p 的空间失活中起作用。酵母中 IMH1 的缺失会减少 GTP 结合的 Arl1p 的量，并导致更少的 Arl1p 驻留在 TGN 上。在生化方面，纯化的 Imh1p 与 Gcs1p（一种 Arl1p GTP 酶激活蛋白（GAP））竞争与 Arl1p 的结合，从而干扰 Gcs1p 对 Arl1p 的 GAP 活性。此外，我们证明 Imh1p 的自我相互作用减弱了 Gcs1p 依赖的 Arl1p 的 GTP 水解。因此，我们提出高尔基糖蛋白 Imh1p 作为一种反馈调节剂来调节 Arl1p 的 GTP 水解。
