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Mammalian Erv46 localizes to the endoplasmic reticulum-Golgi intermediate compartment and to cis-Golgi cisternae
Lelio Orci1, Mariella Ravazzola, Gary J Mack
1Department of Morphology, University Medical Center, 1211 Geneva 4, Switzerland.
Abstract:
Yeast endoplasmic reticulum (ER) vesicle protein Erv46p is a novel membrane protein involved in transport through the early secretory pathway. Investigation of mammalian Erv46 (mErv46) reveals that it is broadly expressed in tissues and protein-secreting cells. By immunofluorescence microscopy, mErv46 displays a crescent-shaped perinuclear staining pattern that is characteristic of the Golgi complex. Quantitative immunoelectron microscopy indicates that mErv46 is restricted to the cis face of the Golgi apparatus and to vesicular tubular structures between the transitional ER and cis-Golgi. Minor amounts of mErv46 reside in ER membranes and later Golgi cisternae. On Brefeldin A treatment, mErv46 redistributes to punctate structures that costain for ERGIC53. Depletion of mErv46 protein by RNA interference caused no apparent structural changes in the intermediate compartment or Golgi complex. These findings place mErv46 in a group of itinerant proteins that cycle between the ER and Golgi compartments such as ERGIC53 and the p24 proteins.
Insights
Mammalian Erv46 (mErv46) is a novel protein localized to the Golgi apparatus, involved in early secretory pathway transport. It cycles between the endoplasmic reticulum and Golgi, similar to other known itinerant proteins.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The early secretory pathway is crucial for protein modification and transport.
- Yeast Erv46p is a known component of this pathway.
- Understanding mammalian homologs provides insights into conserved cellular mechanisms.
Purpose of the Study:
- To investigate the localization and function of mammalian Erv46 (mErv46).
- To determine the role of mErv46 in protein transport between the ER and Golgi.
- To classify mErv46 within the context of known ER-Golgi itinerant proteins.
Main Methods:
- Immunofluorescence microscopy to determine protein localization.
- Quantitative immunoelectron microscopy for precise localization.
- Brefeldin A treatment to study dynamic protein redistribution.
- RNA interference to assess functional impact of protein depletion.
Main Results:
- mErv46 is broadly expressed and localized to the cis-Golgi and ER-Golgi intermediate compartment.
- It resides in vesicular tubular structures and ER membranes.
- Brefeldin A treatment causes redistribution to ERGIC53-positive structures.
- mErv46 depletion does not cause apparent structural Golgi or intermediate compartment changes.
Conclusions:
- mErv46 is an itinerant protein cycling between the ER and Golgi.
- It functions within the early secretory pathway, likely in vesicular transport.
- mErv46 shares characteristics with ERGIC53 and p24 proteins, highlighting conserved transport mechanisms.