Stability of the transamidase complex catalyzing GPI anchoring of proteins
Stability of the transamidase complex catalyzing GPI anchoring of proteins
复制标题
DOI：
10.1016/j.bbrc.2019.03.103
复制
发表时间：
2019-05-07
影响因子：
3.1
通讯作者：
Goto, Satoshi
中科院分区：
文献类型：
--
作者：
Kawaguchi, Kohei;Sato, Tatsuro;Goto, Satoshi
糖基磷脂酰肌醇（GPI）是一种将一些蛋白质锚定在质膜上的糖脂。这种锚定由转酰胺酶复合物（TAC）催化，该复合物由五个亚基组成：PIG-K、GAA 1、PIG-U、PIG-T和PIG-S（图1A）。预测P1 G-K和GAA 1催化GPI锚定蛋白（GPI-AP）的前蛋白与GPI连接的第一和第二步骤。GPI可以通过PIG-U递送，并且当在培养的细胞中过表达时，所有TAC亚基的稳定性需要PIG-T。然而，TAC的蛋白质稳定性尚未使用每个亚基的功能丧失突变体进行分析。在此，我们分析了TAC在每个亚基的敲除和/或敲减突变体中的稳定性。PIG-T和PIG-U或PIG-T和GAA 1是稳定性相互需要的，并且所有三个亚基在没有PIG-S或PIG-K的情况下都是稳定的。然而，这三个亚基对于PIG-S和PIG-K的稳定性都是必需的。相比之下，PIG-S的缺失降低了PIG-K的稳定性，而其他亚基不受影响。PIG-K的减少不影响任何其他亚基。因此，PIG-T、PIG-U和GAA 1可能形成与PIG-S相关的核心复合物，这四个亚基可能稳定PIG-K，触发GPI锚定反应。PIG-K在不存在其他四个亚基的情况下的不稳定性可以确保GPI锚定仅由完全组装的复合物催化。(C)2019爱思唯尔公司All rights reserved.
Glycosylphosphatidylinositol (GPI) is a glycolipid that anchors some proteins to the plasma membrane. This anchoring is catalyzed by a transamidase complex (TAC) composed of five subunits: PIG-K, GAA1, PIG-U, PIG-T, and PIG-S (Fig. 1A). P1G-K and GAA1 are predicted to catalyze the first and second steps during attachment of proproteins of GPI-anchored proteins (GPI-APs) to GPI. GPI may be delivered by PIG-U, and PIG-T is required for stability of all TAC subunits when overexpressed in cultured cells. However, protein stability of TAC has not been analyzed using loss-of-function mutants for each subunit. Herein, we analyzed the stability of TAC in knockout and/or knockdown mutants for each subunit. PIG-T and PIG-U, or PIG-T and GAA1, were mutually required for stability, and all three subunits were stable without PIG-S or PIG-K. However, these three subunits were essential for the stability of both PIG-S and PIG-K. By contrast, loss of PIG-S reduced the stability of PIG-K and left the other subunits unaffected. Reduction of PIG-K did not impact any of the other subunits. Thus, PIG-T, PIG-U, and GAA1 may form a core complex associated by PIG-S, and these four subunits may stabilize PIG-K, triggering GPI anchoring reactions. Instability of PIG-K in the absence of the other four subunits may ensure that GPI anchoring is catalyzed only by the completely assembled complex. (C) 2019 Elsevier Inc. All rights reserved.