Engagement of the B-cell antigen receptor activates STAT through Lyn in a Jak-independent pathway

• Published in: Oncogene Vol. 26; no. 20; pp. 2851 - 2859
• Main Authors: WANG, L, KUROSAKI, T, COREY, S. J
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 03-05-2007; Nature Publishing Group
• Subjects: Animals; Antigens; B-cell receptor; Biological and medical sciences; Cell lines; Cell physiology; Cell proliferation; Cell receptors; Cell signaling; Cell structures and functions; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cells, Cultured; Cellular signal transduction; Chickens; Cytokine receptors; DNA binding proteins; DNA-Binding Proteins - metabolism; Electrophoretic mobility; Fundamental and applied biological sciences. Psychology; Genetic aspects; Genetics; Granulocyte Colony-Stimulating Factor - metabolism; Health aspects; Janus kinase; Janus kinase 2; Janus Kinases - physiology; Kinases; Lymphocytes B; Miscellaneous; Molecular and cellular biology; Null cells; Oncology; Phosphorylation; Phosphotyrosine; Protein Binding; Receptors, Antigen, B-Cell - metabolism; Receptors, Antigen, B-Cell - physiology; Signal Transduction; src-Family Kinases - genetics; src-Family Kinases - physiology; STAT Transcription Factors - metabolism; Stat3 protein; STAT3 Transcription Factor - metabolism; Transcription; Tyrosine; United States; Antigen; Lyn; STAT; Enzyme; Jak; Transferases; B-Lymphocyte; B-cell antigen receptor; Carcinogenesis; Protein-tyrosine kinase; Biological receptor
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1210092

Engagement of the B-cell antigen receptor (BCR) initiated by the Src kinase Lyn triggers rapid signaling cascades, leading to proliferation, differentiation or growth arrest of B cells. The Janus kinase (JAK)-STAT (signal transducer and activator of transcription) pathway, activated through cytokine receptors, mediates similar responses. Hypothesizing that Src and JAK pathways engage in crosstalk in B-cell signaling, we studied wild-type and Lyn-null B-cell lines, which express BCR. We found that activated BCR results in tyrosine phosphorylation of JAK-STAT, which required Lyn. To confirm that STAT activation is not due to JAK, we cloned the chicken homologs of JAK1 and JAK2 and made their antisense constructs. In cells expressing antisense JAK1 and JAK2, tyrosine phosphorylation of STAT was not inhibited following BCR stimulation. Using activation loop-specific phosphotyrosine antibodies, we did not detect phospho-JAK1 and phospho-JAK2 after BCR stimulation. The JAK inhibitor AG490 did not inhibit the tyrosine phosphorylation of Lyn or STAT after BCR simulation. An in vitro phosphorylation assay showed that Lyn directly phosphorylates STAT3. In an electrophoretic mobility shift assay, BCR stimulation led to enhanced DNA binding of the STAT3 in DT40, but not in the Lyn-null cells. We conclude that BCR engagement activates the STAT pathway via Lyn, independent of JAK.