The Journal of Immunology, Vol 147, Issue 4 1171-1179, Copyright © 1991 by American Association of Immunologists

ARTICLES

Cross-linkage of Ly-6A/E induces Ca2+ translocation in the absence of phosphatidylinositol turnover and mediates proliferation of normal murine B lymphocytes

CM Snapper, H Yamada, JJ Mond and CH June
Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.

Ly-6A/E is a phosphatidylinositol (PI)-linked membrane protein whose expression is induced or upregulated on normal murine T and B cells by IFN-gamma. Cross-linkage of Ly-6A/E expressed on normal murine T cells stimulates Ca2+ translocation, and in the presence of a protein kinase C (PKC) activator, lymphokine secretion, and cellular proliferation. Utilizing an anti-Ly-6A/E mAb, we studied the effect of cross-linking Ly-6A/E on IFN-gamma-treated resting B cells, for Ca2+ translocation, PI turnover, and cellular proliferation. Since these events are known to be stimulated by cross-linkage of B cell membrane (m)Ig, we compared the changes mediated through these respective membrane proteins. We show that cross-linkage of B cell Ly-6A/E stimulates a large, rapid, and sustained increase in the concentration of intracellular free calcium ([Ca2+]i) comparable in magnitude, though somewhat delayed, relative to that observed after cross-linking of mIg. Cross-linkage of B cell Ly-6A/E does not, however, stimulate detectable PI turnover, in contrast to PI turnover induced by ligation of mIg. Both the Ly-6A/E- and mIg-mediated increase in [Ca2+]i occur through mobilization of internal Ca2+ stores as well as entry of Ca2+ into the cell from the extracellular compartment. Ly-6A/E-mediated Ca2+ translocation appears to be under the regulation of PKC in that short term pretreatment of B cells with the PKC activator, PMA, inhibits the Ly-6A/E- as well as the mIg-mediated increase in [Ca2+]i, whereas prolonged exposure to PMA, under conditions that lead to depletion of PKC, results in an augmentation in Ca2+ translocation after ligation of either Ly-6A/E or mIg. Co-capping studies indicate that Ly-6A/E and mIg cap independently in the B cell membrane, thus suggesting that the Ly-6A/E-induced effects on Ca2+ translocation are not mediated through simultaneous modulation of mIg. Anti-Ly6A/E, by itself, does not stimulate an increase in [3H]thymidine incorporation by IFN-gamma-treated resting B cells, but induces a striking increase in the presence of PMA. By contrast, anti-Ig by itself stimulates significant increases in [3H]thymidine incorporation that is inhibited by PMA. Thus, Ly-6A/E is a potent mediator of B cell activation that may use a signal transduction system in quiescent B cells that is distinct from that of the Ag receptor.

This article has been cited by other articles:

				K. Kretschmer, A. Jungebloud, J. Stopkowicz, B. Stoermann, R. Hoffmann, and S. Weiss Antibody Repertoire and Gene Expression Profile: Implications for Different Developmental and Functional Traits of Splenic and Peritoneal B-1 Lymphocytes J. Immunol., August 1, 2003; 171(3): 1192 - 1201. [Abstract] [Full Text] [PDF]

				M. M. Khodadoust, K. D. Khan, and A. L. M. Bothwell Complex Regulation of Ly-6E Gene Transcription in T Cells by IFNs J. Immunol., July 15, 1999; 163(2): 811 - 819. [Abstract] [Full Text] [PDF]