Role of ADP ribosylation factor 1 in the assembly and secretion of ApoB-100-containing lipoproteins.
OBJECTIVE
We investigated the role of ADP ribosylation factor 1 (ARF1) in the assembly of very-low-density lipoproteins (VLDLs).


RESULTS
The dominant-negative ARF1 mutant, T31N, decreased the assembly of apoB-100 VLDL 1 (Svedberg floatation units [Sf] 60 to 400) by 80%. The decrease coincided with loss of coatamer I (COPI) from the Golgi apparatus and inhibition of anterograde transport, as demonstrated by time-lapse studies of the vesicular stomatitis virus G protein. The VLDL 1 assembly was also completely inhibited at 15 degrees C. Thus, the antegrade transport is essential for the assembly of VLDL 1. Intracellular localization of N-acetylgalactosaminyl transferase 2 indicated that the Golgi apparatus was at least partly intact when the VLDL assembly was inhibited. Transient transfection with phospholipase D 1 increased the assembly of VLDL 1 and VLDL 2 (Sf 20 to 60). Overexpression of ARF1 in stably transfected McA-RH7777 cells increased the secretion of VLDL 2 but not of VLDL 1, which was dependent on the availability of oleic acid. Secretion of VLDL 1 increased with increasing amounts of oleic acid, and VLDL 2 secretion decreased simultaneously.


CONCLUSIONS
Overexpression of ARF1 increased the assembly of VLDL 2 but not of VLDL 1, whose production was dependent on both anterograde transport and the availability of fatty acids.
Asp
Lennart
L
Department of Medical Biochemistry, Wallenberg Laboratory for Cardiovascular Research, Göteborg University, Göteborg, Sweden.
Magnusson
Björn
B
Rutberg
Mikael
M
Li
Lu
L
Borén
Jan
J
Olofsson
Sven-Olof
SO
D020823:ADP-Ribosylation Factor 1 / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000378:metabolism*; D001692:Biological Transport; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D020755:Coat Protein Complex I / Q000378:metabolism; D015870:Gene Expression; D006056:Golgi Apparatus / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008113:Liver Neoplasms; D009154:Mutation; D019301:Oleic Acid / Q000493:pharmacokinetics; D010739:Phospholipase D / Q000378:metabolism; D051381:Rats
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D020755:Coat Protein Complex I; D008079:Lipoproteins, VLDL; D019301:Oleic Acid; D010739:Phospholipase D; C106801:phospholipase D1; D020823:ADP-Ribosylation Factor 1