Mature VLDL triggers the biogenesis of a distinct vesicle from the trans-Golgi network for its export to the plasma membrane

    Authors

    T. Hossain; A. Riad; S. Siddiqi; S. Parthasarathy;S. A. Siddiqi

    Comments

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    Abbreviated Journal Title

    Biochem. J.

    Keywords

    apolipoprotein B; endoplasmic reticulum; post-Golgi VLDL transport; vesicle (PG-VTV); trans-Golgi network (TGN); triacylglycerol; very; low-density lipoprotein (VLDL); LOW-DENSITY LIPOPROTEIN; TRIGLYCERIDE TRANSFER PROTEIN; ENDOPLASMIC-RETICULUM; APOLIPOPROTEIN-B; RAT HEPATOCYTES; CELL-SURFACE; LIVER-CELLS; COMPLEX; TRAFFICKING; ER; Biochemistry & Molecular Biology

    Abstract

    Post-Golgi trafficking of mature VLDL (very-low-density lipoprotein) is crucial in maintaining normal TAG (triacylglycerol) homoeostasis of hepatocytes; however, the mechanism that regulates the exit of mature VLDL from the TGN (trans-Golgi network) is not known. We developed an in vitro TGN-budding assay that allowed us to examine the formation of secretory vesicles from the TGN in primary rat hepatocytes. We isolated TAG-rich PG-VTVs (post-TGN VLDL transport vesicles) using a continuous sucrose density gradient. PG-VTVs were distributed in low-density fractions, whereas protein transport vesicles were present in relatively higher-density fractions of the same sucrose gradient. EM revealed large intact PG-VTVs ranging 300 350 nm in size. The biogenesis of PG-VTVs from the TGN required cytosol, ATP, GTP hydrolysis and incubation at 37 degrees C. PG-VTVs concentrated the VLDL proteins: apolipoproteins apoB100, apoAIV, apoAI and apoE, but did not contain either albumin or transferrin. Proteinase K treatment did not degrade VLDL core proteins, suggesting that PG-VTVs were sealed. PG-VTVs were able to fuse with and deliver VLDL to the PM (plasma membrane) in a vectorial manner. We conclude that we have identified a new TGN-derived vesicle, the PG-VTV, which specifically transports mature VLDL from the TGN to the PM.

    Journal Title

    Biochemical Journal

    Volume

    459

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    47

    Last Page

    58

    WOS Identifier

    WOS:000333718700005

    ISSN

    0264-6021

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