Sato Takashi, Susuki Seiko, Suico Mary Ann, Miyata Masanori, Ando Yukio, Mizuguchi Mineyuki, Takeuchi Makoto, Dobashi Mizuki, Shuto Tsuyoshi, Kai Hirofumi
Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.
EMBO J. 2007 May 16;26(10):2501-12. doi: 10.1038/sj.emboj.7601685. Epub 2007 Apr 12.
The secretion of transthyretin (TTR) variants contributes to the pathogenesis of amyloidosis because they form aggregates in the extracellular environment. However, the mechanism of how TTR variants pass the quality control system in the endoplasmic reticulum (ER) has not yet been elucidated. We investigated here the mechanism of how TTR passes ER monitoring. Monomeric mutation introduced in TTRs (M-TTRs) resulted in the ER retention of amyloidogenic M-TTRs but not non-amyloidogenic M-TTRs. Retention of amyloidogenic M-TTRs induced the unfolded protein response and upregulated the expression of ER chaperones BiP and glucose-regulated protein (GRP) 94. Additionally, we showed that the ER-retained amyloidogenic M-TTRs are subject to ER-associated degradation. On the other hand, the amyloidogenic TTR variants and non-amyloidogenic M-TTRs were secreted normally. These findings suggest that unlike for wild-type TTR, the ER quality control system may differentially regulate the fate of the TTR variants and their monomeric counterparts.
转甲状腺素蛋白(TTR)变体的分泌会导致淀粉样变性的发病机制,因为它们会在细胞外环境中形成聚集体。然而,TTR变体如何通过内质网(ER)中的质量控制系统的机制尚未阐明。我们在此研究了TTR如何通过ER监测的机制。在TTR(M-TTR)中引入的单体突变导致淀粉样变性M-TTR在内质网中滞留,但非淀粉样变性M-TTR则不会。淀粉样变性M-TTR的滞留诱导了未折叠蛋白反应,并上调了内质网伴侣BiP和葡萄糖调节蛋白(GRP)94的表达。此外,我们表明内质网滞留的淀粉样变性M-TTR会经历内质网相关降解。另一方面,淀粉样变性TTR变体和非淀粉样变性M-TTR正常分泌。这些发现表明,与野生型TTR不同,内质网质量控制系统可能会以不同方式调节TTR变体及其单体对应物的命运。