Clinical Experimental Center, First Affiliated Hospital of Jinan University, No. 613, Huangpu Avenue West, Guangzhou 510630, China.
Institute of Traditional Chinese Medicine & Natural Products, College of Pharmacy, Jinan University, No. 601, Huangpu Avenue West, Guangzhou 510632, China.
Glycobiology. 2018 Jun 1;28(6):374-381. doi: 10.1093/glycob/cwy034.
Malectin is a newly discovered endoplasmic reticulum (ER)-resident lectin, which specifically recognizes Glc2Man9GlcNAc2 on newly synthesized glycoproteins. We have previously demonstrated that malectin forms a complex with ribophorin I for selective retention of misfolded glycoproteins inside the cell. Here, we showed that ribophorin I also functions to regulate the subcellular localization of malectin under various conditions. Even though malectin does not contain an ER-retention signal motif, we found that endogenous malectin mainly localizes in the ER, which is disrupted upon suppression of ribophorin I, leading to its movement from ER to Golgi. In contrast, under ER-stress conditions, malectin mainly localizes in the Golgi, which is restored to ER localization by overexpression of ribophorin I. These results indicate that the subcellular localization of malectin is accurately regulated by the expression level of ribophorin I, which will provide further insights into the understanding of the function of malectin.
甘露糖结合凝集素是一种新发现的内质网（ER）驻留凝集素，它特异性识别新合成糖蛋白上的 Glc2Man9GlcNAc2。我们之前的研究表明，甘露糖结合凝集素与核糖体蛋白 I 形成复合物，用于选择性地将错误折叠的糖蛋白保留在细胞内。在这里，我们发现核糖体蛋白 I 还可以调节甘露糖结合凝集素在各种条件下的亚细胞定位。尽管甘露糖结合凝集素不含 ER 滞留信号基序，但我们发现内源性甘露糖结合凝集素主要定位于 ER，当核糖体蛋白 I 受到抑制时，这种定位会被破坏，导致其从 ER 转移到高尔基体。相反，在 ER 应激条件下，甘露糖结合凝集素主要定位于高尔基体，而过表达核糖体蛋白 I 可将其恢复到 ER 定位。这些结果表明，甘露糖结合凝集素的亚细胞定位是由核糖体蛋白 I 的表达水平精确调节的，这将为进一步理解甘露糖结合凝集素的功能提供依据。
