Department of Bioengineering and Therapeutic Sciences and Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA.
Department of Microbiology and Immunology and the G.W. Hooper Foundation, University of California, San Francisco, San Francisco, CA.
J Cell Biol. 2020 Jan 6;219(1). doi: 10.1083/jcb.201812135.
Glucose transporter 4 (GLUT4) is sequestered inside muscle and fat and then released by vesicle traffic to the cell surface in response to postprandial insulin for blood glucose clearance. Here, we map the biogenesis of this GLUT4 traffic pathway in humans, which involves clathrin isoform CHC22. We observe that GLUT4 transits through the early secretory pathway more slowly than the constitutively secreted GLUT1 transporter and localize CHC22 to the ER-to-Golgi intermediate compartment (ERGIC). CHC22 functions in transport from the ERGIC, as demonstrated by an essential role in forming the replication vacuole of Legionella pneumophila bacteria, which requires ERGIC-derived membrane. CHC22 complexes with ERGIC tether p115, GLUT4, and sortilin, and downregulation of either p115 or CHC22, but not GM130 or sortilin, abrogates insulin-responsive GLUT4 release. This indicates that CHC22 traffic initiates human GLUT4 sequestration from the ERGIC and defines a role for CHC22 in addition to retrograde sorting of GLUT4 after endocytic recapture, enhancing pathways for GLUT4 sequestration in humans relative to mice, which lack CHC22.
葡萄糖转运蛋白 4（GLUT4）在肌肉和脂肪中被隔离，然后在餐后胰岛素的作用下通过囊泡运输释放到细胞表面，以清除血液中的葡萄糖。在这里，我们绘制了人类中这种 GLUT4 运输途径的生物发生图谱，其中涉及网格蛋白同工型 CHC22。我们观察到 GLUT4 通过早期分泌途径的转运速度比组成型分泌的 GLUT1 转运体慢，并将 CHC22 定位到内质网-高尔基体中间区室（ERGIC）。CHC22 在从 ERGIC 运输中的作用，正如 Legionella pneumophila 细菌的复制空泡形成所证明的那样，这需要 ERGIC 衍生的膜。CHC22 与 ERGIC 固定蛋白 p115、GLUT4 和分选蛋白 sorilin 复合物，下调 p115 或 CHC22，但不是 GM130 或 sorilin，会破坏胰岛素反应性 GLUT4 释放。这表明 CHC22 运输从 ERGIC 开始将人类 GLUT4 隔离，并定义了 CHC22 的作用，除了内吞再捕获后 GLUT4 的逆行分类之外，这增强了人类 GLUT4 隔离的途径，与缺乏 CHC22 的小鼠相比。
