ER exit sites in Drosophila display abundant ER-Golgi vesicles and pearled tubes but no megacarriers

• Published in: Cell reports (Cambridge) 2021-09, Vol.36 (11), p.109707-109707, Article 109707
• Main Authors: Yang, Ke, Liu, Min, Feng, Zhi, Rojas, Marta, Zhou, Lingjian, Ke, Hongmei, Pastor-Pareja, José Carlos
• Format: Article
• Language: English
• Subjects: ADP-Ribosylation Factor 1 - metabolism; Animals; Animals, Genetically Modified - genetics; Animals, Genetically Modified - metabolism; Aryl Hydrocarbon Receptor Nuclear Translocator - metabolism; Biological Transport; COP-Coated Vesicles - metabolism; Drosophila - metabolism; Drosophila Proteins - metabolism; Endoplasmic Reticulum - chemistry; Endoplasmic Reticulum - metabolism; ERGIC; Golgi; Golgi Apparatus - chemistry; Golgi Apparatus - metabolism; Golgi Matrix Proteins - metabolism; intermediate compartment; Microscopy, Electron, Scanning; Monomeric GTP-Binding Proteins - metabolism; secretion; Tango1; traffic
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2021.109707

Secretory cargos are collected at endoplasmic reticulum (ER) exit sites (ERES) before transport to the Golgi apparatus. Decades of research have provided many details of the molecular events underlying ER-Golgi exchanges. Essential questions, however, remain about the organization of the ER-Golgi interface in cells and the type of membrane structures mediating traffic from ERES. To investigate these, we use transgenic tagging in Drosophila flies, 3D-structured illumination microscopy (SIM), and focused ion beam scanning electron microscopy (FIB-SEM) to characterize ERES-Golgi units in collagen-producing fat body, imaginal discs, and imaginal discs overexpressing ERES determinant Tango1. Facing ERES, we find a pre-cis-Golgi region, equivalent to the vertebrate ER-Golgi intermediate compartment (ERGIC), involved in both anterograde and retrograde transport. This pre-cis-Golgi is continuous with the rest of the Golgi, not a separate compartment or collection of large carriers, for which we find no evidence. We observe, however, many vesicles, as well as pearled tubules connecting ERES and Golgi. [Display omitted] •Golgi in Drosophila contains a pre-cis-Golgi region equivalent to vertebrate ERGIC•COPII and COPI proteins localize to the center and periphery of ER exit sites, respectively•FIB-SEM imaging shows existence of vesicles consistent with COPI and COPII regular-sized vesicles•In addition to vesicles, FIB-SEM reveals short pearled tubes connecting ERES and Golgi Yang et al. analyzed the organization of the secretory pathway and the ER-Golgi interface in Drosophila using super resolution SIM, APEX-TEM, and FIB-SEM and found, at ER exit sites, regular-sized vesicles and pearled ER-Golgi tubes but no evidence for long-hypothesized larger megacarrier vesicles.