Eugenia Wang

INTERFERON MODULATES CELL STRUCTURE AND FUNCTION

ABSTRACT Interferon treatment alters the structure of the plasma membrane and the cytoskeleton in a variety of cells. These structural changes are associated with modulation of specific functions in human epidermoid carcinoma (HeLa-S3) cells, human skin fibroblasts (FS-4 and ME), transformed mouse fibroblasts (L-929), and thioglycolate-elicited mouse peritoneal macrophages, all treated with homologous beta interferon. The rigidity of the plasma membrane lipid bilayer is increased within 30 min from the beginning of treatment of HeLa cells growing in suspension, but returns tc control level within a few hr. The rigidity increases again by 24 hr after beginning of treatment and persists. Increased abundance of submembranous actin filaments in interferon-treated HeLa-S3 cells is associated with impairment of the mobility and the endocytosis of receptor-bound concanavalin A, slowing of cell proliferation, increased cell size, and increased frequency of multinucleated cells. In interferon-treated human fibroblasts, increased organization of actin-containing microfilaments into bundles is associated with decreased cell locomotion, membrane ruffling, and intracellular movement of organelles, with prolongation of the intermitotic interval, increased cell size, and increased frequency of abortive mitosis giving rise to multinucleated cells. Increased organization of microfilaments in mouse L-929 cells is associated with a marked rise in the frequency of abortive mitoses.

[56] Assays to measure plasma membrane and cytoskeletal changes in interferon-treated cells

Publisher Summary This chapter describes techniques for the measurement of interferon-induced changes in cell size, cytoskeleton, cell surface fibronectin distribution, lateral mobility of cell surface receptors, and fluidity of the plasma membrane. Electron spin resonance (ESR) techniques in combination with the use of probe molecules (spin labels) have been useful in the elucidation of the structural properties of membranes and have been applied to the study of the plasma membrane of interferon-treated cells. These techniques are sensitive to changes in membrane structure and permit measurements on relatively small quantities of viable cells. An ESR signal can be detected from molecules that have an unpaired electron. An optimal ESR spectrum is obtained with the greatest incorporation of spin label into the membrane consistent with minimal structural perturbation. The ESR spectra of C n spin-labeled intact cells are similar to those of purified plasma membrane fractions and are significantly different from those of various cytoplasmic membrane fractions.