Protein phosphorylation in anti-actin IgG and [(IgG)2protein A]2 complex-stimulated L cells.
Phosphorylation of cellular proteins was stimulated in a dose-dependent manner by the surface binding of IgG antibodies to antigens on L cells. Most prominent among the phosphorylated cellular proteins were Mr = 115,000, 93,000, 58,000, 38,000, and 33,000 proteins. Stimulation of protein phosphorylation was maximal at 48 hr of incubation and was preceeded by maximal stimulated uridine incorporation into RNA (0-24 hr) and thymidine incorporation into DNA (24-48 hr), and followed by maximal stimulated cell proliferation occurring at 72 hr (P less than 0.001 for all differences). Modification of the ligand IgG molecule by formation of complexes with protein A (PA) altered the stimulation patterns of protein phosphorylation: [(IgG)2(PA)]2, Mr = 716,000, enhanced and (IgG)(PA), Mr = 200,000, inhibited phosphorylation. The nature of the cell surface antigen(s) was partially clarified by the demonstration that affinity-purified antibodies to cytoskeletal proteins (principally a surface actin molecule) accounted for a significant part of the stimulation effect. Thus, perturbation of the L-cell membrane by certain molecular forms of anti-actin IgG antibody produces a transmembrane signal resulting in an orderly series of metabolic events including enhanced protein phosphorylation at 48 hr occurring just prior to enhanced cell growth.
D000199:Actins / Q000276:immunology*; D000818:Animals; D000906:Antibodies / Q000502:physiology*; D000936:Antigen-Antibody Complex; D004247:DNA / Q000096:biosynthesis; D004306:Dose-Response Relationship, Immunologic; D007074:Immunoglobulin G / Q000276:immunology*; D007739:L Cells / Q000502:physiology*; D051379:Mice; D008970:Molecular Weight; D010750:Phosphoproteins / Q000096:biosynthesis*; D013205:Staphylococcal Protein A / Q000276:immunology; D013997:Time Factors
D000199:Actins; D000906:Antibodies; D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D010750:Phosphoproteins; D013205:Staphylococcal Protein A; D004247:DNA