2-Deoxy-d-glucose: from diagnostics to therapeutics

Glucose is the most common source of cellular energy and a substrate for many biochemical processes. Abnormal glucose signalling has been found in many diseases including cancers and inflammatory diseases. A glucose analog, 2-deoxy-D-glucose (2DG) which interferes with the cellular glucose metabolism has shown promising results both as a diagnostic and therapeutic agent in certain diseased conditions such as cancer, cardiovascular diseases, Alzheimer disease, etc. More recently, Viral-infected cells have also been found to increase their glucose uptake and recently Drug Controller General of India (DCGI) has given approval for the therapeutic use of 2DG in managing severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) infection which has received worldwide attention and has been declared a public health emergency of global concern. An attempt has accordingly been made in this article to review the diagnostic and therapeutic potentials of 2-deoxy-glucose with special emphasis on to its implications in SARS-CoV-2.

Structure of the hexameric fungal plasma membrane proton pump in its auto-inhibited state

The fungal plasma membrane H+-ATPase Pma1 is a vital enzyme, generating a proton-motive force that drives the import of essential nutrients. Auto-inhibited Pma1 hexamers in starving fungi are activated by glucose signalling resulting in phosphorylation of the auto-inhibitory domain. As related P-type ATPases are not known to oligomerise, the physiological relevance of Pma1 hexamers remains unknown. We have determined the structure of hexameric Pma1 from Neurospora crassa by cryo-EM at 3.3 Å resolution, elucidating the molecular basis for hexamer formation and auto-inhibition, and providing a basis for structure-based drug development. Coarse-grained molecular dynamics simulations in a lipid bilayer suggest lipid-mediated contacts between monomers and a substantial protein-induced membrane deformation that could act as a proton-attracting funnel.

Glucokinase Inactivation Paradoxically Ameliorates Glucose Intolerance by Increasing Beta-Cell Mass in db/db Mice

Efficacy of glucokinase activation on glycemic control is limited to a short-term period. One reason might be related with the excess glucose signalling by glucokinase activation towards beta-cells. In this study, we investigated the effect of glucokinase haploinsufficiency on glucose tolerance as well as beta-cell function and mass using a mouse model of type 2 diabetes. Our results showed that <i>db/db</i> mice with glucokinase haploinsufficiency presented amelioration of glucose tolerance by augmented insulin secretion associated with the increase in beta-cell mass when compared with <i>db/db</i> mice. Gene expression profiling, and immunohistochemical and metabolomic analyses revealed that glucokinase haploinsufficiency in the islets of <i>db/db</i> mice was associated with lower expression of stress-related genes, higher expression of transcription factors involved in the maintenance and maturation of beta-cell function, less mitochondrial damage, and a superior metabolic pattern. These effects of glucokinase haploinsufficiency could preserve beta-cell mass under diabetic conditions. These findings verified our hypothesis that optimizing excess glucose signalling in beta-cells by inhibiting glucokinase could prevent beta-cell insufficiency, leading to improving glucose tolerance in diabetes status by preserving beta-cell mass. Therefore, glucokinase inactivation in beta-cells could, paradoxically, be a potential strategy for the treatment of type 2 diabetes.

Glucokinase Inactivation Paradoxically Ameliorates Glucose Intolerance by Increasing Beta-Cell Mass in db/db Mice

Efficacy of glucokinase activation on glycemic control is limited to a short-term period. One reason might be related with the excess glucose signalling by glucokinase activation towards beta-cells. In this study, we investigated the effect of glucokinase haploinsufficiency on glucose tolerance as well as beta-cell function and mass using a mouse model of type 2 diabetes. Our results showed that <i>db/db</i> mice with glucokinase haploinsufficiency presented amelioration of glucose tolerance by augmented insulin secretion associated with the increase in beta-cell mass when compared with <i>db/db</i> mice. Gene expression profiling, and immunohistochemical and metabolomic analyses revealed that glucokinase haploinsufficiency in the islets of <i>db/db</i> mice was associated with lower expression of stress-related genes, higher expression of transcription factors involved in the maintenance and maturation of beta-cell function, less mitochondrial damage, and a superior metabolic pattern. These effects of glucokinase haploinsufficiency could preserve beta-cell mass under diabetic conditions. These findings verified our hypothesis that optimizing excess glucose signalling in beta-cells by inhibiting glucokinase could prevent beta-cell insufficiency, leading to improving glucose tolerance in diabetes status by preserving beta-cell mass. Therefore, glucokinase inactivation in beta-cells could, paradoxically, be a potential strategy for the treatment of type 2 diabetes.

Auxin-mediated protein depletion for metabolic engineering in terpene-producing yeast

In metabolic engineering, loss-of-function experiments are used to understand and optimise metabolism. A conditional gene inactivation tool is required when gene deletion is lethal or detrimental to growth. Here, we exploit auxin-inducible protein degradation as a metabolic engineering approach in yeast. We demonstrate its effectiveness using terpenoid production. First, we target an essential prenyl-pyrophosphate metabolism protein, farnesyl pyrophosphate synthase (Erg20p). Degradation successfully redirects metabolic flux toward monoterpene (C10) production. Second, depleting hexokinase-2, a key protein in glucose signalling transduction, lifts glucose repression and boosts production of sesquiterpene (C15) nerolidol to 3.5 g L−1 in flask cultivation. Third, depleting acetyl-CoA carboxylase (Acc1p), another essential protein, delivers growth arrest without diminishing production capacity in nerolidol-producing yeast, providing a strategy to decouple growth and production. These studies demonstrate auxin-mediated protein degradation as an advanced tool for metabolic engineering. It also has potential for broader metabolic perturbation studies to better understand metabolism.

Biochemical and structural study ofArabidopsishexokinase 1

Hexokinase 1 fromArabidopsis thaliana(AtHXK1) plays a dual role in glycolysis and sugar sensing for vital metabolic and physiological processes. The uncoupling of glucose signalling from glucose metabolism was demonstrated by the analysis of two mutants (AtHXK1G104DandAtHXK1S177A) that are catalytically inactive but still functional in signalling. In this study, substrate-binding experiments indicate that the two catalytically inactive mutants have a high affinity for glucose, and an ordered substrate-binding mechanism has been observed for wild-typeAtHXK1. The structure ofAtHXK1 was determined both in its inactive unliganded form and in its active glucose-bound form at resolutions of 1.8 and 2.0 Å, respectively. These structures reveal a domain rearrangement ofAtHXK1 upon glucose binding. The 2.1 Å resolution structure ofAtHXK1S177Ain the glucose-bound form shows similar glucose-binding interactions as the wild type. A glucose-sensing network has been proposed based on these structures. Taken together, the results provide a structural explanation for the dual functions ofAtHXK1.