两面神激酶(JAK,Janus kinase)是一类酪氨酸蛋白激酶(PTK,protein tyrosine kinase),迄今已发现有4个成员,即JAK1、JAK2、JAK3和TYK2(Tyrosine kinase 2),JAK分子具有7个独特的结构域,从C端到N端依次为JAK同源区1(JAK homology 1,JH1)-JH7[1]。细胞因子与相应受体结合后,JAK与受体偶联并发生酪氨酸磷酸化而激活,活化的JAK能催化受体上特定部位的酪氨酸残基磷酸化,形成信号转导和转录激活因子(Signal Transducer and Activator of Transcription,STAT)等含Src同源区2(SH2,Src JAK (Janus kinase) is a kind of tyrosine kinase (PTK). So far, 4 members have been found, namely JAK1, JAK2, JAK3 and TYK2 (Tyrosine kinase 2) Seven unique domains, from C-terminus to N-terminus, are JAK homology 1 (JH1) -JH7 [1]. Upon binding of cytokines to the corresponding receptors, JAKs are coupled to receptors and are activated by tyrosine phosphorylation. Activated JAKs catalyze the phosphorylation of tyrosine residues at specific sites on the receptor to form signal transduction and transcription Activation factor (Signal Transducer and Activator of Transcription, STAT) containing Src homology region 2 (SH2, Src