Tucholski J, Kuret J, Johnson G V
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 35294-0017, USA.
J Neurochem. 1999 Nov;73(5):1871-80.
Tissue transglutaminase (tTG) is up-regulated in Alzheimer's disease brain and localizes to neurofibrillary tangles with the tau protein. Tau is an in vitro tTG substrate, being cross-linked and/or polyaminated. Further, the Gln and Lys residues in tau that are modified by tTG in vitro are located primarily within or adjacent to the microtubule-binding domains. Considering these and other previous findings, this study was carried out to determine if tau is modified in situ by tTG in human neuroblastoma SH-SY5Y cells, and whether tTG-catalyzed tau polyamination modulates the function and/or metabolism of tau in vitro. For these studies, SH-SY5Y cells stably overexpressing tTG were used. tTG coimmunoprecipitated with tau, and elevating intracellular calcium levels with maitotoxin resulted in a 52 +/- 4% increase in the amount of tTG that coimmunoprecipitated with tau. The increase in association of tTG with tau after treatment with maitotoxin corresponded to a coimmunolocalization of tTG, tTG activity, and tau in the cells. Further, tau was modified by tTG in situ in response to maitotoxin treatment. In vitro polyaminated tau was significantly less susceptible to micro-calpain proteolysis; however, tTG-mediated polyamination of tau did not significantly alter the microtubule-binding capacity of tau. Thus, tau interacts with and is modified by tTG in situ, and modification of tau by tTG alters its metabolism. These data indicate that tau is likely to be modified physiologically and pathophysiologically by tTG, and tTG may play a role in Alzheimer's disease.
组织转谷氨酰胺酶（tTG）在阿尔茨海默病大脑中上调，并与tau蛋白一起定位于神经原纤维缠结中。Tau是tTG的体外底物，会发生交联和/或多胺化。此外，tau中在体外被tTG修饰的Gln和Lys残基主要位于微管结合域内或其附近。考虑到这些及其他先前的研究结果，本研究旨在确定在人神经母细胞瘤SH-SY5Y细胞中tau是否在原位被tTG修饰，以及tTG催化的tau多胺化是否在体外调节tau的功能和/或代谢。对于这些研究，使用了稳定过表达tTG的SH-SY5Y细胞。tTG与tau共免疫沉淀，用 maitotoxin提高细胞内钙水平导致与tau共免疫沉淀的tTG量增加了52±4%。用maitotoxin处理后tTG与tau结合的增加对应于细胞中tTG、tTG活性和tau的共免疫定位。此外，响应maitotoxin处理，tau在原位被tTG修饰。体外多胺化的tau对微钙蛋白酶解的敏感性显著降低；然而，tTG介导的tau多胺化并未显著改变tau的微管结合能力。因此，tau在原位与tTG相互作用并被其修饰，tTG对tau的修饰改变了其代谢。这些数据表明tau可能在生理和病理生理上被tTG修饰，并且tTG可能在阿尔茨海默病中起作用。
