Kurosaki T, Kurosaki M
Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University, Moriguchi 570, Japan.
J Biol Chem. 1997 Jun 20;272(25):15595-8. doi: 10.1074/jbc.272.25.15595.
Bruton's tyrosine kinase (Btk) is required for B cell development and B cell antigen receptor (BCR) function. Cross-linking of BCR induces phosphorylation of Btk at Tyr551 and Tyr223. However, the functional requirement of these phosphorylation for BCR signaling remains unclear. We demonstrate here that mutation of Tyr551, not Tyr223, abrogates the BCR-induced calcium mobilization. Not only Lyn, but also Syk was required for tyrosine phosphorylation of Btk in BCR signaling. These results suggest that transphosphorylation of Btk on Tyr551 is essential for BCR function and that this phosphorylation is mediated through the concerted actions of Lyn and Syk.
布鲁顿酪氨酸激酶（Btk）是B细胞发育和B细胞抗原受体（BCR）功能所必需的。BCR的交联诱导Btk在Tyr551和Tyr223位点磷酸化。然而，这些磷酸化对于BCR信号传导的功能需求仍不清楚。我们在此证明，Tyr551而非Tyr223的突变消除了BCR诱导的钙动员。在BCR信号传导中，不仅Lyn，而且Syk对于Btk的酪氨酸磷酸化都是必需的。这些结果表明，Btk在Tyr551位点的转磷酸化对于BCR功能至关重要，并且这种磷酸化是通过Lyn和Syk的协同作用介导的。
