Biology subjects

Tsives, A.

Publications and source records attributed to Tsives, A..

3 recordsLinked to original sources

bioRxiv2026

iG6PSnFR: A genetically encoded fluorescent sensor for observing glucose-6-phosphate dynamics in living preparations

Glucose-6-phosphate (G6P) is a key intermediate in multiple energetic and anabolic pathways, and quantifying its dynamics is essential for understanding cellular physiology. We have previously developed a syndicate of intensity-based, genetically encoded sensors based on the insertion of circularly permuted GFP into a Venus-flytrap-like analyte-binding protein. Here we use the same approach to develop an intensity-based G6P Sensing Fluorescent Reporter (iG6PSnFR). We present two variants: a G6P-activated sensor that increases fluorescence and a G6P-inactivated sensor that decreases fluorescence. We validate performance across progressively more complex preparations, including purified protein in vitro, immortalized and primary neuronal cultures, isolated pancreatic islets, in an intravital liver model, and finally in vivo in C. elegans neurons. In each context, iG6PSnFR reports G6P changes consistent with expected responses to physiological perturbations.

biochemistry↗

bioRxiv2025

Spatial Partitioning of Core Glycolysis Enables Tissue-Specific Metabolic Programs In Vivo

Tissues exhibit metabolic heterogeneity that tailors conserved pathways to distinct physiological demands, yet how this heterogeneity is achieved in vivo remains poorly understood. Here, we use Caenorhabditis elegans to investigate tissue-specific requirements for glucose-6-phosphate isomerase (GPI-1), a conserved reversible enzyme that links glycolysis and the pentose phosphate pathway (PPP). Tissue-specific metabolic-network modeling predicted differential glycolytic and PPP flux potential across adult tissues and identified tissue-specific biases in GPI-1 reaction directionality. Genetic disruption of gpi-1 produced germline defects consistent with impaired PPP-associated anabolic metabolism and somatic defects consistent with impaired glycolysis, indicating that GPI-1 supports distinct metabolic functions across tissues. We further discovered that two GPI-1 isoforms are differentially expressed and localized: GPI-1A is broadly expressed and cytosolic, whereas GPI-1B is enriched in the germline and localizes to endoplasmic reticulum-associated compartments. Isoform-specific perturbations revealed distinct requirements for GPI-1A and GPI-1B in somatic glycolysis and reproductive physiology. These findings implicate isoform-specific subcellular localization as a possible contributor to the partition of the functions of a conserved reversible enzyme, enabling tissue-specific anabolic and catabolic metabolism in vivo.

cell biology↗

bioRxiv2025

Glycogen metabolism acts in neurons to support glycolytic plasticity

Glycogen is the largest energy reserve in the brain, but the specific role of glycogen in supporting neuronal energy metabolism in vivo is not well understood. We established a system in C. elegans to dynamically probe glycolytic states in single cells of living animals via the use of the glycolytic sensor HYlight and determined that neurons can dynamically regulate glycolysis in response to activity or transient hypoxia. We performed an RNAi screen and identified that PYGL-1, an ortholog of the human glycogen phosphorylase, is required in neurons for glycolytic plasticity. We determined that neurons employ at least two mechanisms of glycolytic plasticity: glycogen-dependent glycolytic plasticity (GDGP) and glycogen-independent glycolytic plasticity (GIGP). We uncover that GDGP is employed under conditions of mitochondrial dysfunction, such as transient hypoxia or in mutants for mitochondrial function. We find that the ability of neurons to plastically regulate glycolysis through cell-autonomous GDGP is important for sustaining the synaptic vesicle cycle. Together, our study reveals that, in vivo, neurons can directly use glycogen as a fuel source to sustain glycolytic plasticity and synaptic function.

neuroscience↗