Briggs S D, Lerner E C, Smithgall T E
Eppley Institute for Research in Cancer and Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
Biochemistry. 2000 Jan 25;39(3):489-95. doi: 10.1021/bi992504j.
Nef is an HIV accessory protein required for high-titer viral replication and AIDS progression. Previous studies have shown that the SH3 domains of Hck and Lyn bind to Nef via proline-rich sequences in vitro, identifying these Src-related kinases as potential targets for Nef in vivo. Association of Nef with Hck causes displacement of the intramolecular interaction between the SH3 domain and the SH2-kinase linker, leading to kinase activation both in vitro and in vivo. In this study, we investigated whether interaction with Nef induces activation of other Src family kinases (Lyn, Fyn, Src, and Lck) following coexpression with Nef in Rat-2 fibroblasts. Coexpression with Nef induced Hck kinase activation and fibroblast transformation, consistent with previous results. In contrast, coexpression of Nef with Lyn was without effect, despite equivalent binding of Nef to full-length Lyn and Hck. Furthermore, Nef was found to suppress the kinase and transforming activities of Fyn, the SH3 domain of which exhibits low affinity for Nef. Coexpression with Nef did not alter c-Src or Lck tyrosine kinase or transforming activity in this system. Differential modulation of Src family members by Nef may produce unique downstream signals depending on the profile of Src kinases expressed in a given cell type.
Nef是一种HIV辅助蛋白，是高滴度病毒复制和艾滋病进展所必需的。先前的研究表明，Hck和Lyn的SH3结构域在体外通过富含脯氨酸的序列与Nef结合，这表明这些与Src相关的激酶是Nef在体内的潜在靶点。Nef与Hck的结合导致SH3结构域与SH2-激酶连接区之间的分子内相互作用发生位移，从而在体外和体内均导致激酶激活。在本研究中，我们调查了在大鼠-2成纤维细胞中与Nef共表达后，与Nef的相互作用是否会诱导其他Src家族激酶（Lyn、Fyn、Src和Lck）的激活。与Nef共表达诱导了Hck激酶激活和成纤维细胞转化，这与先前的结果一致。相比之下，尽管Nef与全长Lyn和Hck的结合相当，但Nef与Lyn的共表达却没有效果。此外，发现Nef抑制Fyn的激酶和转化活性，其SH3结构域对Nef的亲和力较低。在该系统中，与Nef共表达不会改变c-Src或Lck酪氨酸激酶或转化活性。Nef对Src家族成员的差异调节可能会根据给定细胞类型中表达的Src激酶谱产生独特的下游信号。
