Kapeller R, Prasad K V, Janssen O, Hou W, Schaffhausen B S, Rudd C E, Cantley L C
Department of Physiology, Tufts University Medical School, Boston, Massachusetts 02111.
J Biol Chem. 1994 Jan 21;269(3):1927-33.
Src homology 3 (SH3) domains have been recently shown to bind to proline-rich sequences contained in 3BP1, 3BP2, and SOS. In a recent study we demonstrated that phosphatidylinositol 3-kinase (PI 3-kinase) associates with the Fyn SH3 domain. Here we show that p85, the regulatory subunit of PI 3-kinase, binds directly to the SH3 domains of Abl, Lck, Fyn, and p85 itself. An examination of p85 amino acid sequence revealed two proline-rich sequences in its N-terminal region similar to those present in 3BP1, 3BP2, and SOS. To test whether these sequences mediate the association of p85 with SH3 domains two peptides with amino acid composition corresponding to the p85 alpha proline-rich sequences were synthesized and used in competition assays. Both peptides worked equally well in inhibiting the binding of PI 3-kinase activity and p85 alpha to Fyn SH3 domain, whereas a control peptide had no effect. These results indicate that, as in 3BP1 and SOS, the proline-rich sequences in p85 mediate its interaction with SH3 domains. These results also suggest that the SH3 domain of p85 may "self-associate" with the proline-rich motifs of the same subunit as part of the PI 3-kinase regulatory mechanism.
Src同源结构域3（SH3）最近被证明可与包含在3BP1、3BP2和SOS中的富含脯氨酸的序列结合。在最近的一项研究中，我们证明磷脂酰肌醇3激酶（PI 3激酶）与Fyn SH3结构域相关联。在此我们表明，PI 3激酶的调节亚基p85直接与Abl、Lck、Fyn的SH3结构域以及p85自身结合。对p85氨基酸序列的研究揭示，在其N端区域有两个富含脯氨酸的序列，类似于3BP1、3BP2和SOS中存在的序列。为了测试这些序列是否介导p85与SH3结构域的结合，合成了两个氨基酸组成与p85α富含脯氨酸序列相对应的肽，并用于竞争试验。这两种肽在抑制PI 3激酶活性和p85α与Fyn SH3结构域的结合方面效果相同，而对照肽则没有作用。这些结果表明，与3BP1和SOS一样，p85中富含脯氨酸的序列介导其与SH3结构域的相互作用。这些结果还表明，作为PI 3激酶调节机制的一部分，p85的SH3结构域可能与同一亚基的富含脯氨酸基序“自我结合”。
