Regulation by estrogen of synthesis and secretion of apolipoprotein A-I in the chicken hepatoma cell line, LMH-2A.
The synthesis and secretion of apolipoprotein A-I (apoA-I) in response to the treatment with estrogen were investigated in the chicken hepatoma cell line, LMH-2A. Exposure of these cells to exogenous estrogen for up to 48 h results in a decrease of apoA-I production, as evident from Western blotting, immunoprecipitation, and immunofluorescence experiments. Likewise, the secretion of apoA-I is also decreased in estrogen-treated cells when compared to controls. However, under both conditions, the disappearance of the apoprotein from the cells occurs very rapidly and with similar kinetics. The bulk of apoA-I secreted from LMH-2A cells is recovered on lipoprotein particles with a buoyant density of > or =1.10 g/ml, corresponding to HDL and heavy LDL. Interestingly, apoA-I is detectable on apoB-containing lipoproteins by sequential immunoprecipitation, suggesting that the two apoproteins co-reside at least on a subfraction of the secreted particles, or that apoB- and apoA-I-containing particles interact. These interactions are more pronounced in estrogen-treated cells, most likely due to the dramatic estrogen-mediated induction of apoB synthesis and secretion.
Hermann
Marcela
M
Department of Molecular Genetics, Institute of Medical Biochemistry, University and Biocenter Vienna, Dr. Bohr-Gasse 9/2, Vienna A-1030, Austria. mhermann@mol.univie.ac.at
Foisner
Roland
R
Schneider
Wolfgang J
WJ
Ivessa
N Erwin
NE
D000818:Animals; D016632:Apolipoprotein A-I / Q000096:biosynthesis*; D001055:Apolipoproteins B / Q000096:biosynthesis / Q000097:blood / Q000737:chemistry; D002460:Cell Line; D002645:Chickens; D004967:Estrogens / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood / Q000737:chemistry; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008297:Male
D016632:Apolipoprotein A-I; D001055:Apolipoproteins B; D004967:Estrogens; D008075:Lipoproteins, HDL; D004997:Ethinyl Estradiol