B cell receptor directs the activation of NFAT and NF-kappaB via distinct molecular mechanisms.
BCR engagement initiates intracellular calcium ([Ca2+]i) mobilization which is critical for the activation of multiple transcription factors including NF-kappaB and NFAT. Previously, we showed that Bruton's tyrosine kinase (BTK)-deficient (btk-/-) B cells, which display a modestly reduced calcium response to BCR crosslinking, do not activate NF-kappaB. Here we show that BTK is also essential for the activation of NFAT following BCR engagement. Pharmacological mobilization of [Ca2+]i in BTK-deficient DT40 B cells (DT40.BTK) does not rescue BCR directed activation of NF-kappaB and only partially that of NFAT, suggesting existence of additional BTK-signaling pathways in this process. Therefore, we investigated a requirement for BTK in the production of diacylglycerol (DAG). We found that DT40.BTK B cells do not produce DAG in response to BCR engagement. Pharmacological inhibition of PKC isozymes and Ras revealed that the BCR-induced activation of NF-kappaB requires conventional PKCbeta, whereas that of NFAT may involve non-conventional PKCdelta and Ras pathways. Consistent with an essential role for BTK in the regulation of NFAT, B cells from btk-/- mice display defective expression of CD5, a gene under the control of NFAT. Together, these results suggest that BCR employs distinct BTK-dependent molecular mechanisms to regulate the activation of NF-kappaB versus NFAT.
Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
Pierre
P
Antony
James B
JB
Petro
Gianluca
G
Carlesso
Nicholas P
NP
Shinners
John
J
Lowe
Wasif N
WN
Khan
D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D018956:CD5 Antigens / Q000096:biosynthesis / Q000235:genetics; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002645:Chickens; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D004075:Diglycerides / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D051966:Phospholipase C gamma; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000172:deficiency* / Q000235:genetics; D011947:Receptors, Antigen, B-Cell / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D018956:CD5 Antigens; D004268:DNA-Binding Proteins; D004075:Diglycerides; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011947:Receptors, Antigen, B-Cell; D014157:Transcription Factors; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse; D011493:Protein Kinase C; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D018631:ras Proteins