Comparisons of picornavirus-induced modifications of the distribution of radioactive choline among cytoplasmic lipid macromolecules.

Abstract

SUMMARY Radioactive choline was incorporated by HeLa cells into a characteristic distribution of choline-associated lipid macromolecules when cytoplasmic extracts are centrifuged in discontinuous sucrose gradients. The proportional distributions of radioactivity among three peaks in the gradients were altered by infecting the HeLa cells with rhinovirus type 2 and 14, or with poliovirus. Poliovirus infection induced similar distributions of radioactivity in both LLCMK2 and HeLa cells with the greatest radioactivity increase in peaks nearest the tops of the gradients. When the LLCMK2 cells were infected with echovirus 12, the major increase in choline-associated radioactivity was in a peak near the middle of the gradients, in a pattern of distribution that was more similar to that of rhinovirus-infected HeLa cells than to poliovirus-infected LLCMK2 cells. Radioactive glucosamine-labelled, cytoplasmic macromolecules were distributed differently from those labelled with choline in both infected and uninfected cultures, and infection by all four virus strains sharply decreased glucosamine-associated radioactivity in the gradients, suggesting that the synthesis of glucosamine- and choline-containing structures are under different cytoplasmic controls. When these results are taken together with the findings of clearly different patterns of distribution of choline-associated radioactivity in gradients prepared from uninfected HeLa and LLCMK2 cells labelled at 37 °C, and the closer similarity between them when labelled at 34 °C, it appears that choline-containing lipids can have specific temperature-regulated processes in different cell types, and that different viruses may have common and selectively specific modifying effects on the synthesis of cytoplasmic lipid macromolecules.