Hexokinase 2: The preferential target of trehalose-6-phosphate over hexokinase 1.

Cancer-related metabolic features are in part maintained by hexokinase 2 upregulation, which leads to high levels of glucose-6-phosphate (G6P) and is needed to provide energy and biomass to support rapid proliferation. Using a humanized model of the yeast Saccharomyces cerevisiae, we explored how human hexokinase 2 (HK2) behaves under different nutritional conditions. At high glucose levels, yeast presents aerobic glycolysis through a regulatory mechanism known as catabolic repression, which exerts a metabolic adaptation like the Warburg effect. At high glucose concentrations, HK2 did not translocate into the nucleus and was not able to shift the metabolism toward a highly glycolytic state, in contrast to the effect of yeast hexokinase 2 (Hxk2), which is a crucial protein for the control of aerobic glycolysis in S. cerevisiae. During the stationary phase, when glucose is exhausted, Hxk2 is shuttled out of the nucleus, ceasing catabolic repression. Cells harvested at this condition display low glucose consumption rates. However, glucose-starved cells expressing HK2 had an increased capacity to consume glucose. In those cells, HK2 localized to mitochondria, becoming insensitive to G6P inhibition. We also found that the sugar trehalose-6-phosphate (T6P) is a human HK2 inhibitor, like yeast Hxk2, but was not able to inhibit human HK1, the isoform that is ubiquitously expressed in almost all mammalian tissues. In contrast to G6P, T6P inhibited HK2 even when HK2 was associated with mitochondria. The binding of HK2 to mitochondria is crucial for cancer survival and proliferation. T6P was able to reduce the cell viability of tumor cells, although its toxicity was not impressive. This was expected as cell absorption of phosphorylated sugars is low, which might be counteracted using nanotechnology. Altogether, these data suggest that T6P may offer a new paradigm for cancer treatment based on specific inhibition of HK2.

Trehalose Protects against Superoxide Dismutase 1 Proteinopathy in an Amyotrophic Lateral Sclerosis Model.

This work aimed to study the effect of trehalose in protecting cells against Sod1 proteinopathy associated with amyotrophic lateral sclerosis (ALS). Humanized yeast cells in which native Sod1 was replaced by wild-type human Sod1 or an ALS mutant (WT-A4V Sod1 heterodimer) were used as the experimental model. Cells were treated with 10% trehalose (p/v) before or after the appearance of hSod1 proteinopathy induced by oxidative stress. In both conditions, trehalose reduced the number of cells with Sod1 inclusions, increased Sod1 activity, and decreased the levels of intracellular oxidation, demonstrating that trehalose avoids Sod1 misfolding and loss of function in response to oxidative stress. The survival rates of ALS Sod1 cells stressed in the presence of trehalose were 60% higher than in their absence. Treatment with trehalose after the appearance of Sod1 inclusions in cells expressing WT Sod1 doubled longevity; after 5 days, non-treated cells did not survive, but 15% of cells treated with sugar were still alive. Altogether, our results emphasize the potential of trehalose as a novel therapy, which might be applied preventively in ALS patients with a family history of the disease or after diagnosis in ALS patients who discover the disease following the first symptoms.

Glycation modulates superoxide dismutase 1 aggregation and toxicity in models of sporadic amyotrophic lateral sclerosis.

Different SOD1 proteoforms are implicated## in both familial and sporadic cases of Amyotrophic Lateral Sclerosis (ALS), an aging-associated disease that affects motor neurons. SOD1 is crucial to neuronal metabolism and health, regulating the oxidative stress response and the shift between oxidative-fermentative metabolism, which is important for astrocyte-neuron metabolic cooperation. Neurons have a limited capacity to metabolize methylglyoxal (MGO), a potentially toxic side product of glycolysis. MGO is highly reactive and can readily posttranslationally modify proteins, in a reaction known as glycation, impacting their normal biology. Here, we aimed to investigate the effect of glycation on the aggregation and toxicity of human SOD1WT (hSOD1WT). Cells with deficiency in MGO metabolism showed increased levels of hSOD1WT inclusions, displaying also reduced hSOD1WT activity and viability. Strikingly, we also found that the presence of hSOD1WT in stress granules increased upon MGO treatment. The treatment of recombinant hSOD1WT with MGO resulted in the formation of SDS-stable oligomers, specially trimers, and thioflavin-T positive aggregates, which can promote cell toxicity and TDP-43 pathology. Together, our results suggest that glycation may play a still underappreciated role on hSOD1WT and TDP-43 pathologies in sporadic ALS, which could open novel perspectives for therapeutic intervention.