Title

The identification of the SNARE complex required for the fusion of VLDL-transport vesicle with hepatic cis-Golgi

Authors

Authors

S. Siddiqi; A. M. Mani;S. A. Siddiqi

Comments

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Abbreviated Journal Title

Biochem. J.

Keywords

apolipoprotein B (apoB); endoplasmic reticulum (ER); Sec22b; triacylglycerol (TAG); very-low-density lipoprotein-transport vesicle; (VTV); LOW-DENSITY LIPOPROTEINS; ENDOPLASMIC-RETICULUM; APOLIPOPROTEIN-B; MEMBRANE-FUSION; INTERMEDIATE COMPARTMENT; CONFORMATIONAL-CHANGES; HEPG2; CELLS; COPII; PROTEIN; SECRETION; Biochemistry & Molecular Biology

Abstract

VLDLs (very-low-density lipoproteins) are synthesized in the liver and play an important role in the pathogenesis of atherosclerosis. Following their biogenesis in hepatic ER (endoplasmic reticulum), nascent VLDLs are exported to the Golgi which is a physiologically regulatable event. We have previously shown that a unique ER-derived vesicle, the VTV (VLDL-transport vesicle), mediates the targeted delivery of VLDL to the Golgi lumen. Because VTVs are different from other ER-derived transport vesicles in their morphology and biochemical composition, we speculated that a distinct set of SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins would form a SNARE complex which would eventually facilitate the docking/fusion of VTVs with Golgi. Our results show that Sec22b is concentrated in VTVs as compared with the ER. Electron microscopic results show that Sec22b co-localizes with p58 and Sari on the VTV surface. Pretreatment of VTV with antibodies against Sec22b inhibited VTV-Golgi fusion, indicating its role as a v-SNARE (vesicle SNARE). To isolate the SNARE complex, we developed an in vitro docking assay in which VTVs were allowed to dock with the Golgi, but fusion was prevented to stabilize the SNARE complex. After the docking reaction, VTV-Golgi complexes were collected, solubilized in 2 % Triton X-100 and the SNARE complex was co-immunoprecipitated using anti-Sec22b or GOS28 antibodies. A similar to 110 kDa complex was identified in non-boiled samples that was dissociated upon boiling. The components of the complex were identified as Sec22b, syntaxin 5, rBet1 and GOS28. Antibodies against each SNARE component significantly inhibited VTV-Golgi fusion. We conclude that the SNARE complex required for VTV-Golgi fusion is composed of Sec22b, syntaxin 5, rBet1 and GOS28.

Journal Title

Biochemical Journal

Volume

429

Publication Date

1-1-2010

Document Type

Article

Language

English

First Page

391

Last Page

401

WOS Identifier

WOS:000280085000017

ISSN

0264-6021

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