N-linked glycosylation is required for optimal proteolytic activation of membrane-bound transcription factor CREB-H
N-linked glycosylation is required for optimal proteolytic activation of membrane-bound transcription factor CREB-H
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DOI：
10.1242/jcs.067819
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发表时间：
2010-05-01
影响因子：
4
通讯作者：
Jin, Dong-Yan
中科院分区：
文献类型：
--
作者：
Chan, Chi-Ping;Mak, To-Yuen;Jin, Dong-Yan
CREB-H是CREB 3亚家族的肝脏富集的bZIP转录因子。CREB-H通过膜内蛋白水解激活，其去除C-末端跨膜结构域。CREB-H的异常表达与肝癌有关在这项研究中，我们的特点是N-连接的糖基化CREB-H在管腔域的C-末端。我们发现CREB-H在该区域的三个N-连接糖基化位点被修饰。通过定点突变破坏所有三个位点完全消除了CREB-H的N-连接糖基化。CREB-H的非糖基化突变体不是不稳定的、未折叠的或聚集的。在用膜内蛋白水解的激活剂如布雷菲德菌素A和KDEL加尾位点1蛋白酶刺激后，未糖基化或去糖基化的CREB-H在很大程度上未被切割，以无活性形式保留在内质网中，并且不太能够激活由未折叠蛋白应答元件或C-反应蛋白启动子驱动的转录。两者合计，我们的研究结果表明，N-连接的糖基化是通过膜内蛋白水解完全激活CREB-H所必需的。我们的工作还揭示了一个新的机制，调节CREB-H依赖的转录。
CREB-H is a liver-enriched bZIP transcription factor of the CREB3 subfamily. CREB-H is activated by intramembrane proteolysis that removes a C-terminal transmembrane domain. Aberrant expression of CREB-H is implicated in liver cancer. In this study we characterized N-linked glycosylation of CREB-H in the luminal domain at the C-terminus. We found that CREB-H is modified at three N-linked glycosylation sites in this region. Disruption of all three sites by site-directed mutagenesis completely abrogated N-linked glycosylation of CREB-H. The unglycosylated mutant of CREB-H was not unstable, unfolded or aggregated. Upon stimulation with an activator of intramembrane proteolysis such as brefeldin A and KDEL-tailed site 1 protease, unglycosylated or deglycosylated CREB-H was largely uncleaved, retained in an inactive form in the endoplasmic reticulum, and less capable of activating transcription driven by unfolded protein response element or C-reactive protein promoter. Taken together, our findings suggest that N-linked glycosylation is required for full activation of CREB-H through intramembrane proteolysis. Our work also reveals a novel mechanism for the regulation of CREB-H-dependent transcription.