Transient down-regulation of PKC-zeta RNA following crosslinking of membrane IgM on WEHI-231 B lymphoma cells.
Regulation of protein kinase C (PKC) isoform mRNAs has been studied in the immature, murine B lymphoma WEHI-231 by the MAPPing protocol and by slot blot analysis of unamplified mRNA. This membrane IgM (mIgM)-positive cell line has been previously used as a model to study signal transduction by mIgM in immature B lymphocytes and the role of those signals in the induction of immune tolerance in the B cell compartment. Stimulation of the cells by anti-mu antibodies, phorbol ester, or Ca2+ ionophore caused growth arrest and death of the cells. IL 4 and IL 5 slowed the growth of the cells. Of these stimuli, only anti-mu stimulation affected PKC mRNA levels. Anti-mu treatment caused a transient decrease in the amount of PKC-zeta isoform mRNA within 3 hr. Within 24 hr levels returned toward normal. Anti-mu had little or no effect on the expression of mRNA for the alpha, beta, delta, or epsilon isoforms of PKC. WEHI-231 cells do not express PKC-gamma. Although anti-mu treatment blocked progression of the cells from the G0/G1 stage into the S phase of cell cycle, viable sort selected cells in either the G0/G1 or the S/G2/M phases showed no clear difference in the expression of PKC-zeta message. Thus, there is not preferential regulation of expression of PKC-zeta during stages of the cell cycle. The results show that mIgM on WEHI-231 cells can transduce a signal that is not mediated by PKC or Ca2+ mobilization alone. The signal causes transient, selective down-regulation of mRNA encoding the zeta PKC isoform.
Tsutsumi
A
A
Department of Molecular Immunology, Syntex Research, Palo Alto, California 94304.
Freire-Moar
J
J
Ransom
J T
JT
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000737:chemistry*; D016923:Cell Death; D002462:Cell Membrane / Q000737:chemistry; D015536:Down-Regulation; D007075:Immunoglobulin M / Q000737:chemistry*; D007527:Isoenzymes / Q000235:genetics*; D051379:Mice; D011493:Protein Kinase C / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D000888:Antibodies, Anti-Idiotypic; D007075:Immunoglobulin M; D007527:Isoenzymes; D012333:RNA, Messenger; D011493:Protein Kinase C