Modification of the lipid composition of normal and Rous sarcoma virus infected cells: effects on transformation associated membrane properties

Procedures are described for modification of the phospholipid polar head group and fatty acid composition of normal and Rous sarcoma virus-infected chicken embryo fibroblasts. Lipid modification was carried out by growth of cells in delipidated medium containing either polar head group analogues or specific fatty acids. Normal and infected cells displayed similar kinetics of lipid alteration, and the modification was 50% complete in approximately 10 h. Since this is faster than can be accounted for by growth and dilution, extensive turnover of polar head groups and fatty acids must occur in this system. Supplementation with linoleate (18.2) had little or no effect on the growth of cells. Supplementation with the choline analogues N-methylethanolamine and N,N-dimethylethanolamine caused some growth inhibition, but still allowed substantial cellular multiplication. Supplementation with l-2-amino-1-butanol or ethanolamine, or the absence of any choline analogue, significantly inhibited cell growth. Rous sarcoma virus-infected cells showed increased sensitivity to growth inhibition by the supplements and began to detach from the dish after a growth plateau was reached. Growth inhibition could be reversed in all cases by changing to standard medium without lipid supplements. The production of infectious virus in the cells with modified polar head groups was similar to the control value except for the cases of supplementation with l-2-amino-1-butanol, which caused a reduction in virus production to approximately 40%. The effects of lipid modification on various parameters of transformation were examined. Lipid modification had little or no effect on the rate of hexose transport by normal or Rous sarcoma virus-transformed cells, except for ethanolamine which caused a slight drop in transport in the normal cultures. Lipid modification had a variety of effects on the adherence of cells to their substrate, the most dramatic being a decreased adherence in normal cultures without any choline analogue or supplemented with l-2-amino-1-butanol, ethanolamine, or N-methylethanolamine. Accompanying the decreased adherence in the l-2-amino-1-butanol-supplemented cultures was a profound change in morphology: the cells became round and refractile, and their surface displayed numerous blebs, ruffles, and microvilli (as revealed by scanning electron microscopy). Thus, l-2-amino-1-butanol supplementation converted the normal cells into partial phenocopies of transformed cells with respect to their adhesiveness and their morphology.