Zhang Ge, Xiang Meiyi, Gu Liankun, Zhou Jing, Zhang Baozhen, Tian Wei, Deng Dajun
Division of Cancer Etiology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Peking University Cancer Hospital and Institute, Beijing 100142, China.
Proc Natl Acad Sci U S A. 2024 Dec 10;121(50):e2409447121. doi: 10.1073/pnas.2409447121. Epub 2024 Dec 4.
There are three distinct forms of autophagy, namely, macroautophagy, microautophagy, and HSPA8 chaperone-mediated autophagy (CMA). While macroautophagy is widely recognized as a regulator of chromosomal instability (CIN) through various pathways, the contributions of CMA and microautophagy to CIN remain uncertain. , a conserved gene in vertebrates, is frequently mutated and down-regulated in numerous human cancers. This study presents findings demonstrating the interaction between human tetratricopeptide repeat domain 28 (TTC28) and heat shock protein member 8 (HSPA8) and lysosomal-associated membrane protein 2A proteins. The tetratricopeptide repeat domains of TTC28 bind to the C-terminal motif (PTIEEVD) in HSPA8, resulting in the subsequent degradation of TTC28 via CMA/microautophagy. Notably, the baseline frequency of micronuclei (FMN) in human cancer cells with knockout cells was three times greater than that in cells with wild-type (7.7% vs. 2.3%, = 4.86E-09). Furthermore, the overexpression of Ttc28 mitigated the impact of knockout on FMN (11.9% vs. 4.8%, = 2.83E-11). Our findings also demonstrate that CMA has a protective effect on genome stability and that TTC28 plays an essential role in the effect of CMA. These results were further supported by the quantification of γH2AX and comet analyses and the analysis of The Cancer Genome Atlas data via bioinformatics. Mechanistically, TTC28 regulates mitosis and cytokinesis, which are involved in the maintenance of genome integrity by CMA. In conclusion, our study demonstrated that TTC28 is not only an HSPA8-mediated CMA/microautophagy substrate but also essential for maintaining chromosomal stability via CMA. Comprehensive TTC28 downregulation may lead to CIN in cancer cells.
自噬有三种不同形式，即巨自噬、微自噬和HSPA8分子伴侣介导的自噬（CMA）。虽然巨自噬通过多种途径被广泛认为是染色体不稳定（CIN）的调节因子，但CMA和微自噬对CIN的作用仍不确定。TTC28是脊椎动物中的一个保守基因，在许多人类癌症中经常发生突变并下调。本研究呈现了关于人类四肽重复结构域28（TTC28）与热休克蛋白成员8（HSPA8）和溶酶体相关膜蛋白2A之间相互作用的研究结果。TTC28的四肽重复结构域与HSPA8的C末端基序（PTIEEVD）结合，导致TTC28随后通过CMA/微自噬降解。值得注意的是，TTC28基因敲除细胞的人类癌细胞中微核（FMN）的基线频率是野生型细胞的三倍（7.7%对2.3%，P = 4.86E - 09）。此外，Ttc28的过表达减轻了TTC28基因敲除对FMN的影响（11.9%对4.8%，P = 2.83E - 11）。我们的研究结果还表明，CMA对基因组稳定性具有保护作用，并且TTC28在CMA的作用中起关键作用。通过生物信息学对γH2AX进行定量分析、彗星分析以及对癌症基因组图谱数据进行分析，进一步支持了这些结果。从机制上讲，TTC28调节有丝分裂和胞质分裂，而它们通过CMA参与基因组完整性的维持。总之，我们的研究表明，TTC28不仅是HSPA8介导的CMA/微自噬底物，而且对于通过CMA维持染色体稳定性至关重要。TTC28的全面下调可能导致癌细胞中的CIN。
