Cell Reports (Sep 2021)

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

  • Ke Yang,
  • Min Liu,
  • Zhi Feng,
  • Marta Rojas,
  • Lingjian Zhou,
  • Hongmei Ke,
  • José Carlos Pastor-Pareja

Journal volume & issue
Vol. 36, no. 11
p. 109707

Abstract

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Summary: 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.

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