Btk/Tec kinases regulate sustained increases in intracellular Ca super(2+) following B-cell receptor activation

Bruton's tyrosine kinase (Btk) is essential for B-lineage development and represents an emerging family of non-receptor tyrosine kinases implicated in signal transduction events initiated by a range of cell surface receptors. Increased dosage of Btk in normal B cells resulted in a striking enha...

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Published in:The EMBO journal 1998-04, Vol.17 (7), p.1973-1985
Main Authors: Fluckiger, A-C, Li, Zuomei, Kato, R M, Wahl, MI, Ochs, H D, Longnecker, R, Kinet, J-P, Witte, ON, Scharenberg, A M, Rawlings, D J
Format: Article
Language:English
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Summary:Bruton's tyrosine kinase (Btk) is essential for B-lineage development and represents an emerging family of non-receptor tyrosine kinases implicated in signal transduction events initiated by a range of cell surface receptors. Increased dosage of Btk in normal B cells resulted in a striking enhancement of extracellular calcium influx following B-cell antigen receptor (BCR) cross-linking. Ectopic expression of Btk, or related Btk/Tec family kinases, restored deficient extracellular Ca super(2+) influx in a series of novel Btk-deficient human B-cell lines. Btk and phospholipase C gamma (PLC gamma ) coexpression resulted in tyrosine phosphorylation of PLC gamma and required the same Btk domains as those for Btk-dependent calcium influx. Receptor-dependent Btk activation led to enhanced peak inositol trisphosphate (IP sub(3)) generation and depletion of thapsigargin (Tg)-sensitive intracellular calcium stores. These results suggest that Btk maintains increased intracellular calcium levels by controlling a Tg-sensitive, IP sub(3)-gated calcium store(s) that regulates store-operated calcium entry. Overexpression of dominant-negative Syk dramatically reduced the initial phase calcium response, demonstrating that Btk/Tec and Syk family kinases may exert distinct effects on calcium signaling. Finally, co-cross-linking of the BCR and the inhibitory receptor, Fc gamma RIIb1, completely abrogated Btk-dependent IP sub(3) production and calcium store depletion. Together, these data demonstrate that Btk functions at a critical crossroads in the events controlling calcium signaling by regulating peak IP sub(3) levels and calcium store depletion.
ISSN:0261-4189