CD38 ligation induces tyrosine phosphorylation of Bruton tyrosine kinase and enhanced expression of interleukin 5-receptor alpha chain: synergistic effects with interleukin 5.

Abstract

Mouse CD38 has been implicated in the regulation of both B-cell proliferation and protection of B cells from irradiation-induced apoptosis. CD38 ligation on B cells by CS/2, an anti-mouse CD38 monoclonal antibody, induced proliferation, IgM secretion, and tyrosine phosphorylation of Bruton tyrosine kinase in B cells from wild-type mice. B CD38 is a type II transmembrane glycoprotein and is an ectoenzyme that possesses both ADP-ribosyl cyclase and cADP-ribosyl hydrolase activities, which generate cADPribose and ADP-ribose from NADI (1-4). CD38 has been implicated in the regulation of both B-cell proliferation and rescue of B cells from apoptosis (5, 6). A role for CD38 in regulation of B-cell activation has been suggested by analysis using agonistic monoclonal antibody (mAb) to mouse CD38, which mitogenically stimulates resting B cells (5, 6) and induces tyrosine phosphorylation of cellular proteins (7). We have reported that ligation of CD38 by CS/2, an agonistic mAb against mouse CD38, also demonstrated mitogenic activity on resting B cells (8). At present, the molecular mechanisms underlying CD38-mediated activation of B cells are poorly understood.Interleukin 5 (IL-5) is a cytokine that stimulates proliferation and differentiation of B cells, eosinophils, and basophils (9, 10). IL-5 signals through the IL-5 receptor (IL-SR) complex, which is composed of an a chain (IL-5Ra) and a 13chain (11-13). IL-5Ra specifically binds IL-5 and forms with the ( chain, which cannot bind IL-5 by itself, a high-affinity receptor complex indispensable for IL-5 signal transduction (12-17).The (3 chain is shared among receptors for IL-5, IL-3, and granulocyte/macrophage colony-stimulating factor (GM-CSF) (14,18,19). IL-5 induces rapid tyrosine phosphorylation of IL-SR (3 chain, phosphatidylinositol 3-kinase, Shc, Vav, and HS1 and The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.activates B-cell-specific nonreceptor-type Bruton tyrosine (Btk) and JAK2 kinases (20,21 . It is not clear whether aberrant expression of Btk in Xid mice is involved in this impaired B-cell responsiveness. In this study, we have examined the role of Btk activation in signaling through CD38 ligation and the synergistic effect of CD38 and IL-5 on IgM secretion. We show that Btk is tyrosine phosphorylated after CD38 cross-linking. Moreover, CD38 ligation with IL-5 costimulation enhances B-cell proliferation, Blimpl (B-lymphocyte-induced maturation protein) gene expression, and IgM production. MATERIALS AND METHODSReagents. Mouse recombinant IL-5 was prepared and purified using anti-mIL-5 mAb coupled beads as described (11). Rat anti-mouse CD38 mAb, CS/2, and anti-mouse IL-SRa mAb, H7, were prepared as described (8,32). Rat anti-mouse Btk polyclonal antibodies was prepared by immunizing rats with glutathione S-transferase-Btk fusion protein (33). Antiphosphotyrosine mAb, 4G10, was obtained...

A critical role of Lyn and Fyn for B cell responses to CD38 ligation and interleukin 5

“…We have reported that CD38 ligation on B cells by anti-mouse CD38 mAb induced proliferation, IgM secretion, and tyrosine phosphorylation of Bruton tyrosine kinase (Btk) in B cells from wild-type mice. B cells from X chromosome-linked immunodeficient (Xid) mice did not respond at all to anti-CD38 mAb although CD38 expression on these B cells was comparable to that on wild-type B cells (8,9). We infer from these results that Btk activity is involved in B cell triggering after cross-linkage of CD38.…”

“…A role for CD38 in regulation of B cell activation has been suggested by analysis using agonistic mAb to mouse CD38 (5)(6)(7)(8)(9). We have reported that CD38 ligation on B cells by anti-mouse CD38 mAb induced proliferation, IgM secretion, and tyrosine phosphorylation of Bruton tyrosine kinase (Btk) in B cells from wild-type mice.…”

“…IL-5 signals through the IL-5 receptor (IL-5R) complex, which is comprised of an ␣ chain (IL-5R␣) and a ␤ chain (12)(13)(14)(15)(16)(17)(18). Analysis of the synergistic effects of various cytokines with CD38 ligation of B cell activation revealed that IL-5 showed the most potent effect on B cell proliferation, Blimp-1 gene expression, and IgM production (9). Although neither CD38 nor IL-5R carries the catalytic domain for protein tyrosine kinases, CD38 ligation induces activation of Btk (9), and IL-5 activates Btk and JAK2 kinases (18)(19)(20).…”

“…Analysis of the synergistic effects of various cytokines with CD38 ligation of B cell activation revealed that IL-5 showed the most potent effect on B cell proliferation, Blimp-1 gene expression, and IgM production (9). Although neither CD38 nor IL-5R carries the catalytic domain for protein tyrosine kinases, CD38 ligation induces activation of Btk (9), and IL-5 activates Btk and JAK2 kinases (18)(19)(20). The B cells from Xid mice that carry the xid gene with a point mutation in the pleckstrin homology domain of Btk (21,22) have a global defect represented by low responses to CD38 ligation, IL-5, and anti-IgM stimulation (23)(24)(25)(26), further supporting the requirement of Btk in CD38-dependent B cell signaling.…”

“…Cultures were performed in triplicate. The cells were pulse-labeled with [ 3 H]thymidine (0.2 Ci per well; 1 Ci ϭ 37 GBq) during the last 6 h of a 72-h culture period, and incorporation of radioactivity was measured as described (9). Results were expressed as the mean cpm Ϯ SEMs of triplicate cultures.…”