Authors

S. Tiwari; S. Siddiqi;S. A. Siddiqi

Comments

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Abbreviated Journal Title

J. Biol. Chem.

Keywords

TRIGLYCERIDE TRANSFER PROTEIN; CHYLOMICRON RETENTION DISEASE; B-CONTAINING LIPOPROTEINS; PLASMA-MEMBRANE ATPASE; ENDOPLASMIC-RETICULUM; APOLIPOPROTEIN-B; APO-B; COPII COAT; SELECTIVE; EXPORT; GOLGI-APPARATUS; Biochemistry & Molecular Biology

Abstract

Nascent very low density lipoprotein (VLDL) exits the endoplasmic reticulum (ER) in a specialized ER-derived vesicle, the VLDL transport vesicle (VTV). Similar to protein transport vesicles (PTVs), VTVs require coat complex II (COPII) proteins for their biogenesis from the ER membranes. Because the size of the VTV is large, we hypothesized that protein(s) in addition to COPII components might be required for VTV biogenesis. Our proteomic analysis, supported by Western blotting data, shows that a 26-kDa protein, CideB, is present in the VTV but not in other ER-derived vesicles such as PTV and pre-chylomicron transport vesicle. Western blotting and immunoelectron microscopy analyses suggest that CideB is concentrated in the VTV. Our co-immunoprecipitation data revealed that CideB specifically interacts with VLDL structural protein, apolipoprotein B100 (apoB100), but not with albumin, a PTV cargo protein. Confocal microscopic data indicate that CideB co-localizes with apoB100 in the ER. Additionally, CideB interacts with COPII components, Sar1 and Sec24. To investigate the role of CideB in VTV biogenesis, we performed an in vitro ER budding assay. We show that the blocking of CideB inhibits VTV budding, indicating a direct requirement of CideB in VTV formation. To confirm our findings, we knocked down CideB in primary hepatocytes and isolated ER and cytosol to examine whether they support VTV budding. Our data suggest that CideB knockdown significantly reduces VTV biogenesis. These findings suggest that CideB forms an intricate COPII coat and regulates the VTV biogenesis.

Journal Title

Journal of Biological Chemistry

Volume

288

Issue/Number

7

Publication Date

1-1-2013

Document Type

Article

Language

English

First Page

5157

Last Page

5165

WOS Identifier

WOS:000315340400063

ISSN

0021-9258

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