TLR9-activating DNA up-regulates ZAP70 via sustained PKB induction in IgM+ B cells.
In the past, ZAP70 was considered a T cell-specific kinase, and its aberrant expression in B-CLL cells was interpreted as a sign of malignant transformation and dedifferentiation. It was only recently that ZAP70 was detected in normal human B cells. In this study, we show that TLR9-activated B cells resemble B-cell chronic lymphocytic leukemia cells with regard to CD5, CD23, CD25, and heat shock protein 90 expression. Furthermore, stimulatory CpG and GpC DNA oligonucleotides target CD27(+)IgM(+) and CD27(-)IgM(+) B cells (but not IgM(-) B cells) and enhance ZAP70 expression predominantly in the IgM(+)CD27(+) B cell subset. ZAP70 is induced via activation of TLR-7 or -9 in a MyD88-dependent manner, depends on protein kinase B (PKB)/mammalian target of rapamycin signaling and is rapamycin sensitive. Furthermore, ZAP70 expression levels correlate with induction of cyclin A2, prolonged B cell proliferation, and sustained induction of PKB. These events are not observed upon CD40 ligation. However, this deficit can be overcome by the expression of constitutively active PKB, given that CD40 ligation of PKB-transgenic B cells induces B cell proliferation and ZAP70 expression. These results highlight a major difference between CD40- and TLR-7/9-mediated B cell activation and suggest that ZAP70 expression levels in B cells give an estimate of the proliferative potential and the associated PKB availability.
Bekeredjian-Ding
Isabelle
I
Department of Medical Microbiology and Hygiene, University Hospital Heidelberg, Heidelberg, Germany. bekeredjian-ding@uni-heidelberg.de
Doster
Anne
A
Schiller
Martin
M
Heyder
Petra
P
Lorenz
Hanns-Martin
HM
Schraven
Burkhart
B
Bommhardt
Ursula
U
Heeg
Klaus
K
D000276:Adjuvants, Immunologic / Q000235:genetics / Q000502:physiology; D000818:Animals; D016175:B-Lymphocyte Subsets / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D018899:CpG Islands / Q000235:genetics / Q000276:immunology*; D006224:Cricetinae; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis*; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009838:Oligodeoxyribonucleotides / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis*; D051217:Toll-Like Receptor 9 / Q000235:genetics* / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology*; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000502:physiology
D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D007075:Immunoglobulin M; D009838:Oligodeoxyribonucleotides; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D051057:Proto-Oncogene Proteins c-akt