Differential tissue-specific expression of human apoA-I and apoA-II.
To evaluate the sources of high density lipoprotein (HDL) particles containing only apolipoprotein A-I (apoA-I), the synthesis of apoA-I and apolipoprotein A-II (apoA-II) was examined in human liver and small intestine as well as the human intestinally derived cell line, Caco-2. Human liver contained apoA-I, apoA-II as well as apolipoprotein B (apoB) mRNA. In contrast, human adult small intestine total and polyA+ RNA had little or no apoA-II despite the presence of apoA-I and apoB. Intestinal biopsies from normal individuals failed to show de novo apoA-II protein synthesis in the media of organ cultures during [35S]methionine pulse-chase labeling, whereas apoA-I could be readily detected. Caco-2 cells contained apoA-II mRNA and secreted apoA-II protein into the tissue culture media. These data indicate that the primary site of human apoA-II synthesis is in the liver and that the small intestine secretes apoA-I-containing high density lipoproteins.
Eggerman
T L
TL
Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
Hoeg
J M
JM
Meng
M S
MS
Tombragel
A
A
Bojanovski
D
D
Brewer
H B
HB
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000096:biosynthesis* / Q000235:genetics; D015152:Blotting, Northern; D006528:Carcinoma, Hepatocellular; D015342:DNA Probes; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007414:Intestinal Neoplasms; D007421:Intestine, Small / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms; D009924:Organ Culture Techniques; D009928:Organ Specificity; D012333:RNA, Messenger / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; D015342:DNA Probes; D012333:RNA, Messenger