Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, Adelaide, SA, Australia.
J Neurochem. 2014 Jan;128(1):196-204. doi: 10.1111/jnc.12391. Epub 2013 Aug 28.
We have previously shown that following traumatic brain injury (TBI) the presence of the amyloid precursor protein (APP) may be neuroprotective. APP knockout mice have increased neuronal death and worse cognitive and motor outcomes following TBI, which is rescued by treatment with exogenous sAPPα (the secreted ectodomain of APP generated by α-secretase cleavage). Two neuroprotective regions were identified in sAPPα, the N and C-terminal domains D1 and D6a/E2 respectively. As both D1 and D6a/E2 contain heparin binding activity it was hypothesized that this is responsible for the neuroprotective activity. In this study, we focused on the heparin binding site, encompassed by residues 96-110 in D1, which has previously been shown to have neurotrophic properties. We found that treatment with APP96-110 rescued motor and cognitive deficits in APP-/- mice following focal TBI. APP96-110 also provided neuroprotection in Sprague-Dawley rats following diffuse TBI. Treatment with APP96-110 significantly improved functional outcome as well as preserve histological cellular morphology in APP-/- mice following focal controlled cortical impact injury. Furthermore, following administration of APP96-110 in rats after diffuse impact acceleration TBI, motor and cognitive outcomes were significantly improved and axonal injury reduced. These data define the heparin binding site in the D1 domain of sAPPα, represented by the sequence APP96-110, as the neuroprotective site to confer neuroprotection following TBI. The product of α-secretase cleavage of the amyloid precursor protein, sAPPα is neuroprotective following traumatic brain injury (TBI). Of interest was whether this neuroprotective activity could be further delineated to a heparin binding region within sAPPα, corresponding to the region APP96-110 (see diagram demonstrating the domain structure of sAPPα). Indeed treatment with APP96-110 improved functional outcome following TBI, an effect that was not seen with a mutated version of the peptide that had reduced heparin binding affinity.
我们之前已经表明，在创伤性脑损伤 (TBI) 后，淀粉样前体蛋白 (APP) 的存在可能具有神经保护作用。APP 敲除小鼠在 TBI 后神经元死亡增加，认知和运动功能更差，而用外源性 sAPPα（APP 通过 α-分泌酶切割产生的分泌型外显子）治疗可挽救这种情况。在 sAPPα 中鉴定出两个具有神经保护作用的区域，分别是 N 和 C 末端结构域 D1 和 D6a/E2。由于 D1 和 D6a/E2 都含有肝素结合活性，因此假设这是其具有神经保护活性的原因。在这项研究中，我们专注于肝素结合位点，该位点包含 D1 中的残基 96-110，先前已显示其具有神经营养特性。我们发现，用 APP96-110 治疗 APP-/- 小鼠的局灶性 TBI 后，可挽救其运动和认知缺陷。APP96-110 还可在弥漫性 TBI 后为 Sprague-Dawley 大鼠提供神经保护。APP96-110 治疗可显著改善 APP-/- 小鼠的功能结果，并在局灶性皮质撞击损伤后保持组织学细胞形态。此外，在给予弥漫性撞击加速 TBI 后 APP96-110 的大鼠中，运动和认知结果显著改善，轴突损伤减少。这些数据确定了 sAPPα 的 D1 结构域中的肝素结合位点，由 APP96-110 序列表示，为 TBI 后提供神经保护的神经保护位点。淀粉样前体蛋白的 α-分泌酶切割产物 sAPPα 在创伤性脑损伤 (TBI) 后具有神经保护作用。有趣的是，这种神经保护活性是否可以进一步细化为 sAPPα 中的肝素结合区域，对应于 APP96-110 区域（请参见显示 sAPPα 结构域结构的示意图）。事实上，用 APP96-110 治疗可改善 TBI 后的功能结果，而用对肝素结合亲和力降低的突变肽治疗则未见这种效果。
