Inhibition of tissue transglutaminase promotes Aβ-induced apoptosis in SH-SY5Y cells

Abstract

Aim: Tissue transglutaminase (tTG) catalyzes proteins, including β-amyloid (Aβ), to cross-link as a γ-glutamyl-ε-lysine structure isopeptide, which is highly resistant to proteolysis. Thus, tTG plays an important role in protein accumulation in Alzheimer's disease (AD). In the present study, we examined the effect of an irreversible tTG inhibitor, NTU283, on Aβ mimic-induced AD pathogenesis in SH-SY5Y cells. Methods: Western blot and in-cell Western analyses were used to detect tTG and isopeptide (representing the enzyme activity of tTG) protein levels. Moreover, Hoechst and PI co-staining was performed, and caspase-3 and caspase-7 activities and the Bax/Bcl-2 ratio were determined to evaluate the effects of NTU283 on apoptosis. Results:The results confirmed that tTG activity was inhibited by NTU283 20-500 μmol/L in a concentration-dependent manner in SH-SY5Y cells. Contrary to our expectations, however, the isopeptide bonds were increased when cells were co-treated with Aβ and NTU283. In addition, NTU283 alone did not induce apoptosis in SH-SY5Y cells. However, when co-applied with Aβ, NTU283 promoted rather than inhibited Aβ-induced apoptosis. Consistent with the apoptotic rate, pretreating cells with different concentrations of NTU283 and Aβ significantly increased the activities of caspase-3 and caspase-7 as well as the ratio of Bax/Bcl-2. Conclusion: Irreversible inhibition of tTG activity did not block but rather promoted Aβ-induced apoptosis, which indicated that tTG has complex functions in AD pathogenesis.

Sulbactam protects neurons against double neurotoxicity of amyloid beta and glutamate load by upregulating glial glutamate transporter 1

“…These changes suggested the involvement of apoptosis under the double effect of Abeta and glutamate load. Parallel results also demonstrated that Abeta1-42 [35][36][37] and glutamate [37][38][39][40][41] induced apoptosis in neuronal SH-SY5H cells and primary cultured neurons, which manifested as increased BAX/BCL2 ratio and expression of cleaved caspase 3. Together, these ndings suggested the involvement of neuronal necrosis and apoptosis under the double effects of Abeta and glutamate load.…”

Neuroprotective effects of clavulanic acid following permanent bilateral common carotid artery occlusion in rats

“…In this examination, APP overexpressed in rats subjected to 2VO which might be responsible for the generation of extracellular Aβ deposits in the neocortex of 2VO rats. In addition, according to a recent study, treatment of cells with Aβ stimulated apoptotic cells with increased levels of bax as well as caspases 3 and 7 (Zhang, Ding, & Wang, ).…”

Mass spectrometry-based endogenous proteincrosslinking omics

“…酰胺转氨酶催化形成的异肽键交联既可以是分子内交联，也可以是分子间交联 [33,34] 。分子内交联 会改变蛋白质的构象，而分子间交联的形成会导致刚性、稳定和高度不溶性的蛋白质复合物产生 许多生理过程如血液凝固、细胞程序性死亡过程中衰老小体的形成，头发和指甲的形成以及白内 障产生等均与异肽键的形成密切相关。另外很多神经退行性疾病也与异肽键的形成有关联。如患 有阿尔茨海默病(Alzheimer's Disease，AD)患者的大脑通常由于大脑皮层大量神经元的丢失而 萎缩，体积和重量有明显的减少 [35] 。在组织学上其显著的特征是神经性老年斑与神经原纤维缠结。 神经性老年斑的主要成分是具有大量交联的 β-淀粉样蛋白 [36] 。尽管这些交联背后的机制仍缺乏具 体的认识，但大量的蛋白质交联是该病的一些关键特征，鉴于 TG2 催化的交联可导致 AD 相关脑 区乙酰胆碱或 Tau 蛋白的积累和聚集，绘制蛋白质中的异肽键的连接模式或许可以有助于对这些 疾病机制的理解 [37] 。Schmitt 等人利用质谱研究血块样本，将已知的异肽键数目从 1 个增加到了 100 多个，并由此提出了血凝块的溶解是由纤维蛋白原的结合以及丝氨酸蛋白酶抑制剂复合物的 形成来共同调节的 [38] 。…”