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

我们报道了猪基因sky编码非受体型72-kDa PTK (p72^<syk>)，该基因具有独特的结构特征，即存在第二个src同源区2 （SH2）而不是该PTK组其他成员的SH3。我们的工作主要集中在Syk在B细胞表面受体启动的信号转导和血小板之间的关系，因为它们丰富的定位。通过B淋巴细胞的抗原受体（BCR）刺激B淋巴细胞导致其快速增加，并诱导磷脂酰肌醇的增加和胞质游离钙的动员。BCR与两类酪氨酸激酶相关：Src家族激酶和Sky激酶。为了剖析这两种激酶在BCR信号传导中的功能作用，我们建立了syk缺陷细胞和lyn缺陷细胞系。syk缺陷细胞消除了酪氨酸磷酸化磷脂酶C (PLC) - γ，导致没有肌醇，1,4,5-三磷酸（IP3）的产生，以及受体刺激下的钙动员。尽管IP3转换是正常的，但BCR在lyn缺陷细胞上的交联引起了延迟和缓慢的钙动员。这些结果表明Syk介导IP3的生成，而Lyn通过独立于IP3生成的过程调节钙的动员。血小板中Syk的活化并不局限于凝血酶的刺激。血小板活化因子、血栓素A2、小麦胚芽凝集素和胶原蛋白也可活化Syk。这些发现暗示Syk可能是多种受体信号传导的关键分子之一。酪氨酸磷酸化p125^<FAK>后，在整合素受体刺激下Syk激活，提示p125^<FAK>的磷酸化可能由Syk介导。通过观察Syk家族PTKs与Src家族PTKs或FAK家族蛋白的物理关联，进一步强化了这一观点。此外，凝血酶刺激血小板可诱导Syk从细胞质部分快速转移到膜和细胞骨架部分。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活化。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