Bi-Directional Protein Transport Between the Er and Golgi

Abstract

The endoplasmic reticulum (ER) and the Golgi comprise the first two steps in protein secretion. Vesicular carriers mediate a continuous flux of proteins and lipids between these compartments, reflecting the transport of newly synthesized proteins out of the ER and the retrieval of escaped ER residents and vesicle machinery. Anterograde and retrograde transport is mediated by distinct sets of cytosolic coat proteins, the COPII and COPI coats, respectively, which act on the membrane to capture cargo proteins into nascent vesicles. We review the mechanisms that govern coat recruitment to the membrane, cargo capture into a transport vesicle, and accurate delivery to the target organelle.

Mutations in a Highly Conserved Region of the Arf1p ActivatorGEA2Block Anterograde Golgi Transport but Not COPI Recruitment to Membranes

“…It is currently believed that the COPI coat complex in yeast functions primarily in retrograde trafficking from the Golgi back to the ER, and in intra-Golgi retrograde trafficking (Lee et al, 2004). Consistent with the results that the gea2-ts mutants have no defect in retrograde trafficking, COPI was found in membrane structures in these mutants even after 45 min of incubation at the nonpermissive temperature (Figure 4 and our unpublished data).…”

“…Retrograde transport of many proteins is mediated by the COPI coat, a heptameric complex that cycles between membranes and cytoplasm (Bonifacino and LippincottSchwartz, 2003;Duden, 2003;Lee et al, 2004). COPI is recruited to Golgi membranes by Arf1-GTP, which is itself activated by one of a family of guanine-nucleotide exchange factors (GEFs) carrying a Sec7 domain (Jackson and Casanova, 2000).…”

Identification of the Yeast R-SNARE Nyv1p as a Novel Longin Domain-containing Protein

“…The functional and compositional integrity of each organelle is maintained by a continued addition to and selective removal of proteins from these compartments, in a process driven by the selectivity of transport step-specific coat protein complexes and mediated by membrane-bound vesicular carriers (Rothman, 1994). Vesicle coat proteins contain binding sites, which recognize sorting motifs on their select protein cargos and direct the recruitment of these proteins into nascent transport vesicles (Lee et al, 2004;Owen et al, 2004). Subsets of vesicle cargo proteins, the soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), are required for successful targeting and fusion of transport vesicles with their target organelles (Jahn et al, 2003).…”

Rint1 inactivation triggers genomic instability, ER stress and autophagy inhibition in the brain

“…4,6,7 Similarly in case of bi-directional ER-Golgi transport the tethering of the COPII-coated vesicles at Golgi membrane takes place in anterograde transport, when in retrograde transport COPIcoated vesicles are tethered at ER membrane. 8,9 Membrane fusion is again mediated by Rab GTPases and SNAREs and SNARE-associated tethering complexes. One of them is the ZW10 complex composed of RINT1, ZW10 and NAG that has a pivotal role in the retrograde transport in association with ER SNAREs Syntaxin 18, p31 and Sec22b.…”