Action of novel non-receptor type protein-tyrosine kinase, p72^<syk>in immune cells.

我们已经报道了一个编码非受体类型72 kDa PTK(P72^&lt；SYK&gt；)的猪基因sky，它有一个独特的结构特征，即存在第二个src同源区2(SH2)而不是SH3。由于Syk的丰富定位，我们在很大程度上集中在Syk在B细胞和血小板表面受体启动的信号转导背景下的关系。BCR与两类酪氨酸激酶相关：SRC家族和Sky激酶。为了分析这两种类型的激酶在BCR信号转导中的功能作用，我们建立了Syk缺陷细胞系和Lyn缺陷细胞系。Syk基因缺陷的细胞取消了酪氨酸磷酸化磷脂酶C(PLC)-γ，导致没有肌醇，1，4，5-Tris…更多的磷酸盐(IP3)生成，以及受体刺激下的钙移动。BCR在LYN缺陷细胞上的交联会引起延迟和缓慢的钙移动，尽管IP3的转化动力学正常。这些结果表明，Syk介导IP3的生成，而Lyn通过一个独立于IP3的过程来调节钙离子的移动。血小板活化因子、血栓素A2、麦芽凝集素和胶原蛋白也能激活Syk。这些发现表明，Syk可能是各种受体信号作用的关键分子之一。在整合素受体刺激下，p125^&lt；FAK&gt；酪氨酸磷酸化后，Syk被激活，提示p125^&lt；FAK&gt；的磷酸化可能是由Syk介导的。加强了这一观点，观察到Syk家族PTKs与Src家族PTKs或FAK家族蛋白的物理联系。此外，凝血酶对血小板的刺激导致Syk从胞浆部分快速移位到膜和细胞骨架部分。这种Syk向膜和细胞骨架部分的募集可能有助于凝血酶诱导的Syk的激活。较少

We have reported a porcine gene sky encoding a non-receptor type 72-kDa PTK (p72^<syk>) which has a distinct structural character, that is the presence of the second src homology region 2 (SH2) instead of SH3, from other members of this group of PTK.Our efforts have in large part focused on the relationship between Syk in the context of surface receptor-initiated signal transduction in B cell and platelet because of their abundant localization.Stimulation of B lymphocytes through their antigen receptor (BCR) result in rapid increases and induces both an increase of phosphatidylinositol and mobilization of cytoplasmic free calcium. The BCR associates with two classes of tyrosine kinase : Src family kinase and Sky kinase. To dissect the functional roles of these two types of kinase in BCR signaling, Syk-deficient cell and Lyn-deficient cell lines were established. Syk-deficient cells abolished the tyrosine phosphorylation phospholipase C (PLC) -gamma, resulting in no inositol, 1,4,5-tris … More phosphate (IP3) generation, as well as calcium moblization upon receptor stimulation. Crosslinking of BCR on Lyn-deficient cells evoked a delayd and slow calcium moblization, despite the normal kinetics of IP3 turnover. These results demonstrated that Syk mediates IP3 generation, whereas Lyn regulates calcium mobization through a process independent of IP3 generation.Activation of Syk in platelets is not restricted to thrombin stimulation. Platelet activating factor, thromboxane A2, wheat germ agglutinin, and collagen also activate Syk. These findings imply that Syk may be one of the key molecules through which various receptor signaling acts. Tyrosine phosphorylation of p125^<FAK> is followed by Syk activation upon integrin receptor stimulation, suggesting that phosphorylation of p125^<FAK> may be mediated by Syk. Reinforcing this idea, the physical association of Syk family PTKs with Src family PTKs or FAK family protein is observed. Furthermore, stimulation of platelets by thrombin induces the rapid translocation of Syk from the cytosolic fraction to the membrane and cytoskeletal fraction. This recruitment of Syk to membrane and cytoskeletal fraction may contribute to the thrombininduced activation of Syk. Less