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首页> 外文期刊>Molecular and Cellular Biology >In vivo and in vitro specificity of protein tyrosine kinases for immunoglobulin G receptor (FcgammaRII) phosphorylation.
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In vivo and in vitro specificity of protein tyrosine kinases for immunoglobulin G receptor (FcgammaRII) phosphorylation.

机译：蛋白酪氨酸激酶在体内和体外对免疫球蛋白G受体（FcgammaRII）磷酸化的特异性。

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Human B cells express four immunoglobulin G receptors, FcgammaRIIa, FcgammaRIIb1, FcgammaRIIb2, and FcgammaRIIc. Coligation of either FcgammaRII isoform with the B-cell antigen receptor (BCR) results in the abrogation of B-cell activation, but only the FcgammaRIIa/c and FcgammaIIb1 isoforms become phosphorylated. To identify the FcgammaRII-phosphorylating protein tyrosine kinase (PTK), we used the combination of an in vitro and an in vivo approach. In an in vitro assay using recombinant cytoplasmic tails of the different FcgammaRII isoforms as well as tyrosine exchange mutants, we show that each of the BCR-associated PTKs (Lyn, Blk, Fyn, and Syk) shows different phosphorylation patterns with regard to the different FcgammaR isoforms and point mutants. While each PTK phosphorylated FcgammaRIIa/c, FcgammaRIIb1 was phosphorylated by Lyn and Blk whereas FcgammaRIIb2 became phosphorylated only by Blk. Mutants lacking both tyrosine residues of the immune receptor tyrosine-based activation motif (ITAM) of FcgammaRIIa/c were not phosphorylated by Blk and Fyn, while Lyn-mediated phosphorylation was dependent on the presence of the C-terminal tyrosine of the ITAM. Results obtained in assays using an FcgammaR- B-cell line transfected with wild-type or mutated FcgammaRIIa demonstrated that exchange of the C-terminal tyrosine of the ITAM of FcgammaRIIa/c was sufficient to abolish FcgammaRIIa/c phosphorylation in B cells. Additionally, we could show that Lyn and Fyn bind to FcgammaRIIa/c, with the ITAM being necessary for association. Comparison of the phosphorylation pattern of each PTK observed in vitro with the phosphorylation pattern observed in vivo suggests that Lyn is the most likely candidate for FcgammaRIIa/c and FcgammaRIIb1 phosphorylation in vivo.
机译：人B细胞表达四种免疫球蛋白G受体，FcgammaRIIa，FcgammaRIIb1，FcgammaRIIb2和FcgammaRIIc。任一种FcgammaRII亚型与B细胞抗原受体（BCR）的结合导致B细胞活化的废止，但只有FcgammaRIIa / c和FcgammaIIb1亚型被磷酸化。为了鉴定FcgammaRII磷酸化蛋白酪氨酸激酶（PTK），我们使用了体外和体内方法的组合。在使用不同FcgammaRII亚型和酪氨酸交换突变体的重组胞质尾部进行的体外测定中，我们显示了每个BCR相关的PTK（Lyn，Blk，Fyn和Syk）在不同的磷酸化方面均显示出不同的磷酸化模式FcgammaR同工型和点突变体。尽管每个PTK都将FcgammaRIIa / c磷酸化，但FcgammaRIIb1被Lyn和Blk磷酸化，而FcgammaRIIb2仅被Blk磷酸化。 FcgammaRIIa / c的基于免疫受体基于酪氨酸的活化基序（ITAM）的两个酪氨酸残基均未被Blk和Fyn磷酸化，而Lyn介导的磷酸化则取决于ITAM C末端酪氨酸的存在。使用野生型或突变的FcgammaRIIa转染的FcgammaR- B细胞系进行分析的结果表明，FcgammaRIIa / c的ITAM的C端酪氨酸交换足以消除B细胞中的FcgammaRIIa / c磷酸化。此外，我们可以证明Lyn和Fyn与FcgRamIIa / c结合，而ITAM对于关联是必需的。体外观察到的每种PTK的磷酸化模式与体内观察到的磷酸化模式的比较表明，Lyn是体内FcgammaRIIa / c和FcgammaRIIb1磷酸化最可能的候选者。

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