Mitochondrial acetyl-CoA acetyltransferase 1 promotes the Warburg effect

描述（由申请人提供）：癌症/白血病细胞中从氧化磷酸化到有氧糖酵解的代谢转换被认为部分是由于线粒体功能减弱，这被认为是通过抑制丙酮酸脱氢酶复合物（PDC）来实现的。丙酮酸脱氢酶A （PDHA）是PDC的第一个也是最重要的酶组分，它将丙酮酸转化为乙酰辅酶A，然后进入克雷布斯循环。PDHA活性受到几个丝氨酸位点磷酸化的负调控。PDH激酶1 （PDHK1）磷酸化PDHA导致PDC失活，而PDH磷酸酶1 （PDP1）去磷酸化可恢复PDC活性。尽管PDHK1已被Myc和HIF-1a上调，但致癌信号如何抑制PDC调节癌细胞代谢仍不甚清楚。有趣的是，我们的蛋白质组学研究显示，在癌细胞中，PDP1和PDHA分别被K202和K321位点的乙酰化抑制。此外，我们发现线粒体乙酰辅酶a乙酰转移酶1 （ACAT1）是上游酶，可乙酰化并抑制PDP1和PDHA，从而抑制PDC通量。此外，我们发现致癌的FGFR1磷酸化并激活ACAT1。在癌细胞中稳定敲低ACAT1导致糖酵解减少，OXPHOS增加，癌细胞增殖和肿瘤生长减少。因此，我们的假设是，FGFR1等致癌TKs磷酸化并激活线粒体ACAT1，通过赖氨酸乙酰化抑制PDHA和PDP1，从而减弱PDC功能，促进Warburg效应和肿瘤生长。这代表了一个新的概念，即致癌TKs的转化信号至少部分可以通过调节关键下游效应物的赖氨酸乙酰化水平来介导。提出了三个具体目的：(1)确定fgfr1依赖性酪氨酸磷酸化ACAT1是否对ACAT1激活和促进癌症代谢和肿瘤生长重要；(2)阐明ACAT1结合、乙酰化和抑制PDP1和/或PDHA的分子机制；(3)检测癌细胞中acat1依赖性赖氨酸乙酰化PDHA和PDP1是否足以促进Warburg效应和肿瘤生长。

DESCRIPTION (provided by applicant): The metabolic switch from oxidative phosphorylation to aerobic glycolysis in cancer/leukemia cell has been suggested to be due to, in part, attenuated mitochondrial function, which is suggested to be achieved through inhibition of pyruvate dehydrogenase complex (PDC). Pyruvate dehydrogenase A (PDHA) is the first and most important enzyme component of PDC, which converts pyruvate to acetyl-CoA that subsequently enters into the Krebs cycle. PDHA activity is negatively regulated by phosphorylation at several serine sites. Phosphorylation of PDHA by PDH kinase 1 (PDHK1) results in the inactivation of PDC, while dephosphorylation by PDH phosphatase 1 (PDP1) restores PDC activity. Although PDHK1 has been suggested to be upregulated by Myc and HIF-1a, how oncogenic signals inhibit PDC to regulate cancer cell metabolism still remains largely unknown. Interestingly, our proteomics studies revealed that in cancer cells, PDP1 and PDHA are inhibited by acetylation at K202 and K321, respectively. Moreover, we identified mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1) as the upstream enzyme that acetylates and inhibits PDP1 and PDHA, and consequently PDC flux. Furthermore, we found that oncogenic FGFR1 phosphorylates and activates ACAT1. Stable knockdown of ACAT1 in cancer cells results in decreased glycolysis and increased OXPHOS, as well as reduced cancer cell proliferation and tumor growth. Thus, our hypothesis is that oncogenic TKs such as FGFR1 phosphorylate and activate mitochondrial ACAT1 to inhibit PDHA and PDP1 via lysine acetylation, which consequently attenuates PDC function to promote the Warburg effect and tumor growth. This represents a new concept that the transforming signals of oncogenic TKs could be mediated at least in part through regulation of lysine acetylation levels of key downstream effectors. Three Specific Aims are proposed: (1) To determine whether FGFR1-dependent tyrosine phosphorylation of ACAT1 is important for ACAT1 activation and promotion of cancer metabolism and tumor growth; (2) To elucidate the molecular mechanisms by which ACAT1 binds to, acetylates and inhibits PDP1 and/or PDHA; (3) To examine whether ACAT1-dependent lysine acetylation of PDHA and PDP1 in cancer cells is sufficient to promote the Warburg effect and tumor growth.