Abrams C S, Zhao W
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104.
J Biol Chem. 1995 Jan 6;270(1):333-9. doi: 10.1074/jbc.270.1.333.
The Src homology 2 (SH2) and Src homology 3 (SH3) domain are approximately 50% conserved in various Src family kinase members. Several lines of evidence suggest that in Src these domains are sequence motifs that direct substrate recognition, regulate kinase activity, or control subcellular localization. We sought to investigate the function of the homology domains in human Lyn, and to determine whether the differences between various SH3 domains affect function. To do this, we generated variant forms of Lyn lacking SH2 and SH3 domains, and created chimeras in which the SH3 domains in human c-Src and Lyn were replaced with SH3 domains from other family members. In contrast to similar deletions in Src, forms of Lyn lacking SH2 or SH3 had decreased kinase activity. The SH3 chimeras all had individual characteristics. Insertion of the Blk SH3 domain into Lyn restored kinase activity, while insertion of the Fyn or Src SH3 into Lyn enhanced the kinase activity 2-3-fold. Insertion of the Lyn SH3 into Src also doubled kinase activity. Expression of the Lyn-Src SH3 chimera in mammalian cells induced cell transformation. This study 1) demonstrates that the regulation of Lyn is different than Src, and 2) provides new evidence that despite their homology, there are important functional differences between the SH3 domains of the various Src family members.
Src同源2（SH2）结构域和Src同源3（SH3）结构域在各种Src家族激酶成员中约有50%的保守性。多项证据表明，在Src中，这些结构域是指导底物识别、调节激酶活性或控制亚细胞定位的序列基序。我们试图研究人Lyn中同源结构域的功能，并确定各种SH3结构域之间的差异是否会影响其功能。为此，我们构建了缺失SH2和SH3结构域的Lyn变异体形式，并构建了嵌合体，其中人c-Src和Lyn中的SH3结构域被其他家族成员的SH3结构域所取代。与Src中的类似缺失不同，缺乏SH2或SH3的Lyn形式的激酶活性降低。SH3嵌合体都具有各自的特点。将Blk SH3结构域插入Lyn可恢复激酶活性，而将Fyn或Src SH3插入Lyn可使激酶活性提高2至3倍。将Lyn SH3插入Src也可使激酶活性加倍。Lyn-Src SH3嵌合体在哺乳动物细胞中的表达诱导了细胞转化。本研究1）表明Lyn的调节与Src不同，2）提供了新的证据，即尽管各种Src家族成员的SH3结构域具有同源性，但它们在功能上存在重要差异。
