Department of Biochemistry and Microbiology, Nelson Mandela University, P.O. Box 77000, Port Elizabeth 6031, South Africa.
Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
Toxins (Basel). 2017 Dec 14;9(12):400. doi: 10.3390/toxins9120400.
Misincorporation of β--methylamino-l-alanine (BMAA) into proteins has been proposed to be a mechanism of toxicity to explain the role of BMAA in neurodegenerative disease development. However, studies have shown that all detectable BMAA can be removed from proteins by SDS-PAGE purification and that the toxicity of l-canavanine cannot be reproduced in prokaryotes or in a rat pheochromocytoma cell line, strongly indicating that the misincorporation hypothesis of BMAA should be re-investigated. The aim of this study was therefore to determine if BMAA misincorporates into proteins in cells of human origin with subsequent misincorporation-type toxicity. Almost complete loss of viability in response to exposure to l-4-fluorophenylalanine and l-m-tyrosine was observed in all of the cell lines, corresponding to a concentration-dependent increase of the analogues in protein extracts from exposed cells. In contrast, BMAA exposure resulted in slight toxicity in one of the cell lines but the observed toxicity was not the result of misincorporation of BMAA into proteins, as no BMAA was detected in any of the SDS-PAGE purified protein extracts that were obtained from the cells following BMAA exposure. The results show that BMAA is not misincorporated into human proteins and that misincorporation is not a valid mechanism of toxicity.
β--甲基氨基--L--丙氨酸（BMAA）掺入蛋白质被认为是其毒性作用的机制，用于解释 BMAA 在神经退行性疾病发展中的作用。然而，研究表明 SDS-PAGE 纯化可去除所有可检测到的 BMAA，并且 l-刀豆氨酸的毒性不能在原核生物或大鼠嗜铬细胞瘤细胞系中重现，这强烈表明 BMAA 的错误掺入假说应重新研究。因此，本研究的目的是确定 BMAA 是否在人源细胞中掺入蛋白质，随后产生错误掺入型毒性。在所有细胞系中，暴露于 l-4-氟苯丙氨酸和 l-m-酪氨酸均导致细胞活力几乎完全丧失，这与暴露细胞蛋白提取物中类似物的浓度依赖性增加相对应。相比之下，BMAA 暴露仅在其中一种细胞系中引起轻微毒性，但观察到的毒性不是 BMAA 掺入蛋白质的结果，因为在 BMAA 暴露后从细胞中获得的任何 SDS-PAGE 纯化蛋白质提取物中均未检测到 BMAA。结果表明，BMAA 不会掺入人蛋白，并且错误掺入不是毒性的有效机制。
