Lipid composition and molecular species of sialic acids of a mouse cell line (JLS-V9) and its ouabain-resistant mutant.

Some properties of a mouse cell line (JLS-V9) and its ouabain-resistant mutant clone (JLS-V9OR) were compared. Specific activities of (Na+ + K+)-ATPase (EC 3.6.1.3) of the cell homogenate, particulate fraction and the plasma membrane fraction were 1.12, 1.72 and 8.75 mu mol/h per mg protein, respectively, in the parent cell and 0.97, 1.68 and 9.36 mu mol/h per mg protein in the mutant cell. The half-maximal concentration of ouabain for the inhibition of the (Na+ + K+)-ATPase was 3.4 . 10(-5) M in the parent cell and 4.0 . 10(-4) M in the resistant clone. The contents of phospholipid and cholesterol on a basis of protein in the mutant were 135 and 105% of those in the parent cell. The mutant's monohexosylceramide (HexCer), lactosylceramide (LacCer), trihexosylceramide (GbOse3Cer) and sialyllactosylceramide (GM3) were 111, 145, 274 and 114% of those of the parent cell. Sialic acids of GM3, analyzed by GC-MS, were 98% N-acetylneuraminic and 2% N-glycolylneuraminic acids in the parent cell, whilst 69% N-acetylneuraminic and 31% N-glycolylneuraminic acids in the mutant clone. The in vivo syntheses of these glycolipids were confirmed by the incorporation of radioactive galactose. No significant difference in fatty acid composition was observed between the two cell types. Neutral glycolipids contained mainly 24:0, 24:1, 22:0 and 16:0, whilst in GM3 18:0 and 18:1 predominated. These results show that the lipid content per mg protein is elevated in the ouabain-resistant cell compared to the parent cell.