Borg J P, Ooi J, Levy E, Margolis B
Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor 48109, USA.
Mol Cell Biol. 1996 Nov;16(11):6229-41. doi: 10.1128/MCB.16.11.6229.
The phosphotyrosine interaction (PI) domains (also known as the PTB, or phosphotyrosine binding, domains) of Shc and IRS-1 are recently described domains that bind peptides phosphorylated on tyrosine residues. The PI/PTB domains differ from Src homology 2 (SH2) domains in that their binding specificity is determined by residues that lie amino terminal and not carboxy terminal to the phosphotyrosine. Recently, it has been appreciated that other cytoplasmic proteins also contain PI domains. We now show that the PI domain of X11 and one of the PI domains of FE65, two neuronal proteins, bind to the cytoplasmic domain of the amyloid precursor protein ((beta)APP). (beta)APP is an integral transmembrane glycoprotein whose cellular function is unknown. One of the processing pathways of (beta)APP leads to the secretion of A(beta), the major constituent of the amyloid deposited in the brain parenchyma and vessel walls of Alzheimer's disease patients. We have found that the X11 PI domain binds a YENPTY motif in the intracellular domain of (beta)APP that is strikingly similar to the NPXY motifs that bind the Shc and IRS-1 PI/PTB domains. However, unlike the case for binding of the Shc PI/PTB domain, tyrosine phosphorylation of the YENPTY motif is not required for the binding of (beta)APP to X11 or FE65. The binding site of the FE65 PI domain appears to be different from that of X11, as mutations within the YENPTY motif differentially affect the binding of X11 and FE65. Using site-directed mutagenesis, we have identified a crucial residue within the PI domain involved in X11 and FE65 binding to (beta)APP. The binding of X11 or FE65 PI domains to residues of the YENPTY motif of (beta)APP identifies PI domains as general protein interaction domains and may have important implications for the processing of (beta)APP.
Shc和IRS-1的磷酸酪氨酸相互作用（PI）结构域（也称为PTB，即磷酸酪氨酸结合结构域）是最近发现的能结合酪氨酸残基磷酸化肽段的结构域。PI/PTB结构域与Src同源2（SH2）结构域不同，在于其结合特异性由磷酸酪氨酸氨基端而非羧基端的残基决定。最近发现其他细胞质蛋白也含有PI结构域。我们现在证明，两种神经元蛋白X11的PI结构域和FE65的一个PI结构域与淀粉样前体蛋白（β-APP）的细胞质结构域结合。β-APP是一种整合跨膜糖蛋白，其细胞功能尚不清楚。β-APP的一种加工途径导致Aβ的分泌，Aβ是阿尔茨海默病患者脑实质和血管壁中沉积的淀粉样蛋白的主要成分。我们发现X11的PI结构域结合β-APP细胞内结构域中的YENPTY基序，该基序与结合Shc和IRS-1的PI/PTB结构域的NPXY基序惊人地相似。然而，与Shc的PI/PTB结构域结合情况不同，β-APP与X11或FE65结合不需要YENPTY基序的酪氨酸磷酸化。FE65的PI结构域的结合位点似乎与X11不同，因为YENPTY基序内的突变对X11和FE65的结合有不同影响。通过定点诱变，我们确定了PI结构域内一个参与X11和FE65与β-APP结合的关键残基。X11或FE65的PI结构域与β-APP的YENPTY基序残基的结合将PI结构域确定为一般的蛋白质相互作用结构域，可能对β-APP的加工具有重要意义。
