TFG regulates inner COPII coat recruitment to facilitate anterograde secretory protein transport

• DOI: 10.1091/mbc.e24-06-0282
• Publication Date: 2024-07-10T15:55:20Z
• Authors: William Kasberg; Peter Luong; Kayla Minushkin; Iryna Pustova; Kevin A. Swift; Meixian Zhao; Anjon Audhya
• Keywords: COPII; Coat; Vesicular Transport Proteins; COPI

Coat protein complex II (COPII) governs the initial steps of biosynthetic secretory transport from endoplasmic reticulum (ER), facilitating movement a wide variety cargoes. Here, we demonstrate that Trk-fused gene (TFG) regulates rate at which inner COPII coat proteins are concentrated ER subdomains. Specifically, in cells lacking TFG, GTPase-activating (GAP) Sec23 accumulates more rapidly budding sites on as compared with control cells, potentially altering normal timing GTP hydrolysis Sar1. Under these conditions, anterograde trafficking several cargoes is delayed, irrespective their predicted size. We propose TFG controls local, freely available pool during formation and limits its capacity to prematurely destabilize complexes ER. This function enables it act akin rheostat, promoting ordered recruitment Sec23, critical for efficient cargo export.