Figure 6 from The cargo receptors Surf4, endoplasmic reticulum-Golgi intermediate compartment (ERGIC)-53, and p25 are required to maintain the architecture of ERGIC and Golgi. | Semantic Scholar (2024)

This work characterized mammalian p28, a γ subfamily member of p24 proteins, which was shown to localize to the ERGIC similar like ERG IC-53, and concluded that p28 is besides coatomer, tethers and SNARE proteins, necessary for compact Golgi ribbon formation.

It is argued that specific cargo-receptor interactions give rise to distinct transport carriers, which in turn regulate the ER-to-Golgi trafficking kinetics and demonstrate the fine-tuning of protein trafficking and localization via its primary structure.

An overview of receptor-mediated transport of secretory proteins from the ER to the Golgi is provided, with a focus on the current understanding of two mammalian cargo receptors: the LMAN1–MCFD2 complex and SURF4, and their roles in human health and disease.

Results show that the formation of a Golgi ribbon requires the structural membrane protein p28 in addition to previously identified SNAREs, coat proteins and tethers, and that silencing p28 prevents protein exchange between Golgi stacks during reassembly after Brefeldin A‐induced Golgi breakdown.

It is shown biochemically that the p24 complex associates at the ER with other cargo receptors in a COPII-dependent manner, forming high-molecular weight multireceptor complexes, providing an additional layer of regulation of secretory cargo selectivity during ER export.

It is shown that Arabidopsis p24δ5/δ9 and HDEL ligands shift the steady-state distribution of the K/HDEL receptor ERD2 from the Golgi to the ER, showing a role for p24 δ5 in retrograde Golgi-to-ER transport.

COPI could be a promising target for the development of antivirals against SARS-CoV-2 and suggest COPI as a critical player in facilitating the transport of SARS-CoV-2 progeny virions from the ERGIC.

It is proposed that p24δ5 and p24β2 interact with each other at ER export sites for ER exit and coupled transport to the Golgi apparatus, which would imply coupled trafficking at the ER–Golgi interface.

Interestingly, this mutant showed a constitutive activation of the unfolded protein response (UPR) and the transcriptional upregulation of the COPII subunit gene SEC31A, which may help the plant to cope with the transport defects seen in the absence of p24 proteins.

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A 32-kDa protein termed ERGIC-32 is a novel cycling membrane protein with sequence hom*ology to Erv41p and Erv46p, two proteins enriched in COPII vesicles of yeast, and it is proposed that ERG IC-32 functions as a modulator of the hErv41-hErv46 complex by stabilizing hErV46.

The ERGIC-53 cytoplasmic domain on CD4 lead to increased ER-staining by immunofluorescence microscopy indicating that this domain alone cannot provide for unbiased recycling through the ER- ERG IC-cis-Golgi compartments.

A stable compartment model in which ER-derived cargo is first shuttled from ER-exit sites to stationary ERGIC clusters in a COPII-dependent step and subsequently to the Golgi in a second vesicular transport step can better accommodate previous morphological and functional data on ER-to-Golgi traffic.

The Golgi apparatus is a highly complex organelle comprised of a stack of cisternal membranes on the secretory pathway from the ER to the cell surface and it is found that TMP21, p24a, and gp25L, members of the p24 cargo receptor family, are present in complexes with GRasP55 and GRASP65 in vivo.

The results suggest that the ERGIC is a dynamic membrane system composed of a constant average number of clusters and that the major recycling pathway of ERG IC-53 bypasses the Golgi apparatus.

It is shown that a cathepsin-Z-related glycoprotein binds to the recycling, mannose-specific membrane lectin ERGIC-53, indicating that ERG IC-53 may function as a receptor facilitating ER-to-ERGIC transport of soluble glycop protein cargo.

The identification of golgin-84 as a novel mitotic target and its role in the assembly and maintenance of the Golgi ribbon in mammalian cells are suggested.

The results suggest that the recycling of ERGIC-53 is required for efficient intracellular transport of a small subset of glycoproteins, but it does not appear to be essential for the majority of glyCoproteins.

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