Expression and secretion of chicken apolipoprotein AI in transfected COS cells.
A full-length chicken apolipoprotein A-I (apoAI) cDNA has been cloned into an expression vector, pRSVapoAI. This plasmid was transfected into a monkey kidney (COS-1) cell line in order to study apolipoprotein-lipid assembly. Chicken apoAI is the major apolipoprotein of chicken high-density lipoprotein (HDL), which is less complex in apolipoprotein content than the HDL of human plasma. The transient transfected COS-1 cells synthesized and secreted authentic plasma apoAI. Under serum-free medium conditions, COS cells secreted only proapoAI. A small portion (15%) of the secreted apoAI floated at a density 1.07-1.20 g/ml. Upon incubation with fetal bovine serum at 10 degrees C, a majority of the apoAI was recovered in the HDL density (1.06-1.20 g/ml) region. Secreted apoAI was labeled when transfected COS cells were incubated with [U-14C]palmitate, but the incorporation of radioactivity was not the result of fatty acid acylation through ester bond formation. These results indicate that heterologous COS-1 cells are capable of synthesizing and secreting apoAI, and that intracellular association of apoAI with lipids is not necessary for secretion.
Dixon
J L
JL
Lindsley F. Kimball Research Institute, New York Blood Center, NY 10021.
Battini
R
R
Ferrari
S
S
Redman
C M
CM
Banerjee
D
D
D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D002645:Chickens; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression; D007163:Immunosorbent Techniques; D008055:Lipids / Q000097:blood; D008969:Molecular Sequence Data; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010957:Plasmids; D011498:Protein Precursors / Q000378:metabolism; D014162:Transfection
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D008055:Lipids; D010169:Palmitic Acids; D011498:Protein Precursors; D019308:Palmitic Acid