我们以前报道过一种必需的DNA修复酶的活性丧失,多核苷酸激酶3'-磷酸酶(PNKP),导致亨廷顿病(HD)和脊髓小脑共济失调3型(SCA3)患者脑基因组中双链断裂(DSB)的积累。在这里,我们记录了PNKP与磷酸果糖激酶果糖-2,6-双磷酸酶3(PFKFB3)的核同工型相互作用,将果糖-6-磷酸(F6P)转化为果糖-2,6-二磷酸(F2,6BP),一种有效的糖酵解变构调节剂。PFKFB3的消耗明显消除了PNKP活性,从而影响PNKP介导的转录偶联的非同源末端连接(TC-NHEJ)。在HD和SCA3患者大脑的核提取物中,PFKFB3和F2,6BP水平均显着降低。外源性F2,6BP恢复了这些样品的脑核提取物中的PNKP活性。此外,将F2,6BP递送到HD小鼠纹状体来源的神经元细胞中,恢复了PNKP活性,转录的基因组完整性和细胞活力。因此,我们推测F2,6BP在体内充当PNKP的适当功能以及从而脑健康的辅因子。因此,我们的结果为探索F2,6BP和相关化合物用于治疗polyQ疾病的治疗用途提供了令人信服的理由。
Huntington\'s disease (HD) and spinocerebellar ataxia type 3 (SCA3) are the two most prevalent polyglutamine (polyQ) neurodegenerative diseases, caused by CAG (encoding glutamine) repeat expansion in the coding region of the huntingtin (HTT) and ataxin-3 (ATXN3) proteins, respectively. We have earlier reported that the activity, but not the protein level, of an essential DNA repair enzyme, polynucleotide kinase 3\'-phosphatase (PNKP), is severely abrogated in both HD and SCA3 resulting in accumulation of double-strand breaks in patients\' brain genome. While investigating the mechanistic basis for the loss of PNKP activity and accumulation of DNA double-strand breaks leading to neuronal death, we observed that PNKP interacts with the nuclear isoform of 6-phosphofructo-2-kinase fructose-2,6-bisphosphatase 3 (PFKFB3). Depletion of PFKFB3 markedly abrogates PNKP activity without changing its protein level. Notably, the levels of both PFKFB3 and its product fructose-2,6 bisphosphate (F2,6BP), an allosteric modulator of glycolysis, are significantly lower in the nuclear extracts of post-mortem brain tissues of HD and SCA3 patients. Supplementation of F2,6BP restored PNKP activity in the nuclear extracts of patients\' brain. Moreover, intracellular delivery of F2,6BP restored both the activity of PNKP and the integrity of transcribed genome in neuronal cells derived from striatum of HD mouse. Importantly, supplementing F2,6BP rescued the HD phenotype in Drosophila, suggesting F2,6BP to serve in vivo as a cofactor for the proper functionality of PNKP and thereby, of brain health. Our results thus provide a compelling rationale for exploring the therapeutic use of F2,6BP and structurally related compounds for treating polyQ diseases.