High and stable ATP levels prevent aberrant intracellular protein aggregation

Abstract

23ATP is the main source of chemical energy in all life and is maintained at several millimolar 24 in eukaryotic cells. However, the mechanisms responsible for and physiological relevance of 25 this high and stable concentration of ATP remain unclear. We herein demonstrate that 26 AMP-activated protein kinase (AMPK) and adenylate kinase (ADK) cooperate to maintain 27 cellular ATP levels regardless of glucose concentrations. Single cell imaging of ATP-reduced 28 yeast mutants revealed that ATP concentrations in these mutants underwent stochastic and 29 transient depletion of ATP repeatedly, which induced the cytotoxic aggregation of 30 endogenous proteins and pathogenic proteins, such as huntingtin and α-synuclein. Moreover, 31 pharmacological elevations in ATP levels in an ATP-reduced mutant prevented the 32 accumulation of α-synuclein aggregates and its cytotoxicity. The removal of cytotoxic 33 aggregates depended on proteasomes, and proteasomal activity cooperated with AMPK or 34 ADK to resist proteotoxic stresses. The present results provide the first evidence to show that 35 cellular ATP homeostasis ensures proteostasis and revealed that stochastic fluctuations in 36 cellular ATP concentrations contribute to cytotoxic protein aggregation, implying that AMPK 37 and ADK are important factors that prevent proteinopathies, such as neurodegenerative 38 diseases. 39 40 2019); however, it currently remains unclear whether ATP-dependent protein 51 solubilization/desolubilization play any significant roles in cell physiology. 52 53 We recently established a reliable imaging technique to quantify intracellular ATP 54 concentrations in single living yeast cells using the genetically encoded fluorescent ATP 55 biosensor QUEEN (Yaginuma, Kawai et al., 2014), which enables long-term evaluations of 56 ATP homeostasis in individual cells (Takaine et al., 2019). Our findings demonstrated that 57 intracellular ATP concentrations did not vary within a yeast population grown in the same 58 culture (Takaine et al., 2019), which was in contrast to the large variations observed in 59 intracellular ATP concentrations within a bacterial cell population (Yaginuma et al., 2014). 60 Moreover, intracellular ATP concentrations in individual living yeast cells were stably and 61 robustly maintained at approximately 4 mM, irrespective of carbon sources and cell cycle 62 stages, and temporal fluctuations in intracellular ATP concentrations were small ( Takaine et 63 al., 2019). Based on these findings, we hypothesized that an exceptionally robust mechanism 64 may exist to precisely regulate ATP concentrations in eukaryotes. It also remains unclear why 65 ATP is stably maintained at a markedly higher concentration than the K m (Michaelis constant) 66 required for the enzymatic activity of almost all ATPases (Edelman, Blumenthal et al., 1987), 67 and the consequences associated with failed ATP homeostasis in living organisms have not 68 yet been elucidated. 69 70The most promising candidate regulator of ATP homeostasis is AMP-activated prote...

Adenylate Kinase and Metabolic Signaling in Cancer Cells

“…Particularly, AMP signaling to AMP-activated protein kinase (AMPK) plays a critical role in adjusting ATP-producing and ATP-consuming processes (90, 94) (Figure 1). In several cancers, it has been demonstrated that AMPK, a master regulator of cellular energy homeostasis, possesses tumor suppressor function (95)(96)(97) (98). On the other end, AMP-deaminase (AMPD) and 5 ′ -nucleotidase (5 ′ -NT) suppress AMPK via decreasing AMP cellular levels (22,99,100).…”

Melatonin: Regulation of Biomolecular Condensates in Neurodegenerative Disorders

“…Voltage-dependent anion channels (VDACs) located in the mitochondrial outer membrane (MOM) [ 41 ] and adenine nucleotide translocators (ANTs) on the inner mitochondrial membranes (IMM) [ 42 , 43 ] facilitate the export of ATP into cytosol where ATP accumulation has been observed to be the highest [ 44 ]. The high physiological concentration of ATP in cytoplasm may be used to control the pathological aggregation of macromolecules that coacervate as a result of transient interactions during LLPS in the cytoplasm and nucleus [ 45 , 46 ]. A major hallmark of ALS/FTD is the presence of FUS inclusion in the cytoplasm.…”