Biology subjects

Klyachko, V.

Publications and source records attributed to Klyachko, V..

8 recordsLinked to original sources

bioRxiv2025

Astrocytic Cholesterol Fine-Tunes the Balance of Different Modes of Synaptic Exo- and Endocytosis

Cholesterol is essential for organization of neurotransmitter release machinery, yet how it regulates the balance among different forms of synaptic exo- and endocytosis remains poorly understood. Moreover, which pre-synaptic processes rely on neuronal vs astrocyte-derived cholesterol is unknown. Using nanoscale-precision imaging of single-vesicle release in hippocampal synapses we demonstrate that astrocytic cholesterol is a critical determinant of both temporal and spatial aspects of presynaptic dynamics by differentially modulating the two main forms of synchronous release, uni-vesicular (UVR) and multi-vesicular (MVR), effectively fine-tuning their balance. Disruption of astrocytic cholesterol trafficking to neurons combined with its re-supplementation demonstrated that astrocyte-derived cholesterol is necessary and sufficient to determine the UVR/MVR balance. Moreover, astrocytic cholesterol determines the spatial distribution of vesicle release by modulating utilization of different release sites across the active zone. Astrocytic cholesterol also regulates the balance of the two main forms of single-vesicle endocytosis, fast and ultra-fast. These findings suggest that astrocytic cholesterol supply is a critical modulator of synaptic strength that fine-tunes the balance of different forms of synaptic vesicle exo- and endocytosis. HighlightsO_LIAstrocytic cholesterol determines the balance of uni- and multi-vesicular release C_LIO_LICholesterol levels modulate spatial organization of vesicle release C_LIO_LIAstrocytic cholesterol controls the balance of fast and ultra-fast endocytosis C_LIO_LIAstrocytic cholesterol is necessary and sufficient for exo- and endocytosis balance C_LI

neuroscience↗

bioRxiv2024

Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission

Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep, intense circuit activity, or dietary restrictions, posing significant metabolic stress. Here, we demonstrate that the mammalian brain utilizes pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability within a neuron and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation which in turn modulates mitochondrial pyruvate uptake. Importantly, our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in synaptic transmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval, functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of synaptic transmission in hippocampal terminals. HIGHLIGHTSO_LISerum pyruvate is taken up by the brain and efficiently oxidized in the TCA cycle. C_LIO_LIThe mitochondrial pyruvate carrier (MPC) is essential for presynaptic energy metabolism. C_LIO_LIAcetylation of the MPC complex modulates mitochondrial pyruvate uptake. C_LIO_LIMPC activity regulates the release and retrieval of synaptic vesicles in nerve terminals. C_LI

neuroscience↗

bioRxiv2023

Metabolic Regulation of Single Synaptic Vesicle Exo- and Endocytosis in Hippocampal Synapses

Glucose has long been considered a primary source of energy for synaptic function. However, it remains unclear under what conditions alternative fuels, such as lactate/pyruvate, contribute to powering synaptic transmission. By detecting individual release events in cultured hippocampal synapses, we found that mitochondrial ATP production from oxidation of lactate/pyruvate regulates basal vesicle release probability and release location within the active zone (AZ) evoked by single action potentials (APs). Mitochondrial inhibition shifted vesicle release closer to the AZ center, suggesting that the energetic barrier for vesicle release is lower in the AZ center that the periphery. Mitochondrial inhibition also altered the efficiency of single AP evoked vesicle retrieval by increasing occurrence of ultrafast endocytosis, while inhibition of glycolysis had no effect. Mitochondria are sparsely distributed along hippocampal axons and we found that nerve terminals containing mitochondria displayed enhanced vesicle release and reuptake during high-frequency trains, irrespective of whether neurons were supplied with glucose or lactate. Thus, synaptic terminals can entirely bypass glycolysis to robustly maintain the vesicle cycle using oxidative fuels in the absence of glucose. These observations further suggest that mitochondrial metabolic function not only regulates several fundamental features of synaptic transmission but may also contribute to modulation of short-term synaptic plasticity. HighlightsO_LISynapses can sustain neurotransmission across various activity levels by bypassing glycolysis and utilizing oxidative fuels. C_LIO_LIMitochondria, but not glycolysis, regulate release probability and nanoscale organization of vesicle release within the active zone. C_LIO_LIMitochondrial inhibition increases the occurrence of vesicle retrieval via ultra-fast endocytosis. C_LIO_LIMitochondrial localization in nerve terminals enhances vesicle release and retrieval in the absence of glucose, representing a form of synaptic plasticity. C_LI

neuroscience↗

bioRxiv2023

Circuit-based intervention corrects excessive dentate gyrus output in the Fragile X mouse model

Abnormal cellular and circuit excitability is believed to drive many core phenotypes in fragile X syndrome (FXS). The dentate gyrus is a brain area performing critical computations essential for learning and memory. However, little is known about dentate circuit defects and their mechanisms in FXS. Understanding dentate circuit dysfunction in FXS has been complicated by the presence of two types of excitatory neurons, the granule cells and mossy cells. Here we report that loss of FMRP markedly decreased excitability of dentate mossy cells, a change opposite to all other known excitability defects in excitatory neurons in FXS. This mossy cell hypo-excitability is caused by increased Kv7 function in Fmr1 KO mice. By reducing the excitatory drive onto local hilar interneurons, hypo-excitability of mossy cells results in increased excitation/inhibition ratio in granule cells and thus paradoxically leads to excessive dentate output. Circuit-wide inhibition of Kv7 channels in Fmr1 KO mice increases inhibitory drive onto granule cells and normalizes the dentate output in response to physiologically relevant theta-gamma coupling stimulation. Our study suggests that circuit-based interventions may provide a promising strategy in this disorder to bypass irreconcilable excitability defects in different cell types and restore their pathophysiological consequences at the circuit level.

neuroscience↗

bioRxiv2023

Sirtuin3 ensures the metabolic plasticity of neurotransmission during glucose deprivation

Neurotransmission is an energetically expensive process that underlies cognition. During intense electrical activity or dietary restrictions, glucose levels in the brain plummet, forcing neurons to utilize alternative fuels. However, the molecular mechanisms of neuronal metabolic plasticity remain poorly understood. Here, we demonstrate that glucose-deprived neurons activate the CREB and PGC1 transcriptional program that induces the expression of the mitochondrial deacetylase Sirtuin 3 (Sirt3) both in vitro and in vivo. We show that Sirt3 localizes to axonal mitochondria and stimulates mitochondrial oxidative capacity in hippocampal nerve terminals. Sirt3 plays an essential role in sustaining synaptic transmission in the absence of glucose by powering the retrieval of synaptic vesicles after release. These results demonstrate that the transcriptional induction of Sirt3 ensures the metabolic plasticity of synaptic transmission. HighlightsO_LIGlucose deprivation drives transcriptional reprogramming of neuronal metabolism via CREB and PGC1. C_LIO_LIGlucose or food deprivation trigger the neuronal expression of mitochondrial deacetylase sirtuin 3 (Sirt3) both in vitro and in vivo. C_LIO_LISirt3 stimulates oxidative ATP synthesis in nerve terminals. C_LIO_LISirt3 sustains the synaptic vesicle cycle in the absence of glucose. C_LI

neuroscience↗

bioRxiv2022

Two forms of asynchronous release with distinctive spatiotemporal dynamics in central synapses

Asynchronous release is a ubiquitous form of neurotransmitter release that persists for tens to hundreds of milliseconds after an action potential (AP). How asynchronous release is organized and regulated at the synaptic active zone (AZ) remains debatable. Using nanoscale-precision imaging of individual release events in rat hippocampal synapses, we observed two spatially distinct subpopulations of asynchronous events, ~75% of which occurred inside the AZ and with a bias towards the AZ center, while ~25% occurred outside of the functionally defined AZ, i.e., ectopically. The two subpopulations also differed markedly in temporal properties, with ectopic events occurring at significantly longer time intervals from synchronous events. Both forms of asynchronous release did not, to a large extent, utilize the same release sites as synchronous events. Both asynchronous event subpopulations also differ from synchronous events in some aspects of exo-endocytosis coupling. Specifically, for synchronous but not asynchronous events, coupling with the fast calcium-dependent endocytosis had a gradient decreasing from the AZ center towards its periphery. These results identify two distinct subpopulations of asynchronous release events with distinctive spatiotemporal organization and coupling to endocytic mechanisms.

neuroscience↗

bioRxiv2020

Myosin V regulates spatial localization of different forms of neurotransmitter release in central synapses

Synaptic active zone (AZ) contains multiple specialized release sites for vesicle fusion. The utilization of release sites is regulated to determine spatiotemporal organization of the two main forms of synchronous release, uni-vesicluar (UVR) and multi-vesicular (MVR). We previously found that the vesicle-associated molecular motor myosin V regulates temporal utilization of release sites by controlling vesicle anchoring at release sites (Maschi et al, 2018). Here we show that acute inhibition of myosin V shifts preferential location of vesicle docking away from AZ center towards periphery, and results in a corresponding spatial shift in utilization of release sites during UVR. Similarly, inhibition of myosin V also reduces preferential utilization of central release sites during MVR, leading to more spatially distributed and temporally uniform MVR that occurs farther away from the AZ center. Thus myosin V regulates both temporal and spatial utilization of release sites during two main forms of synchronous release.

neuroscience↗

bioRxiv2019

Spatiotemporal dynamics of multi-vesicular release is determined by heterogeneity of release sites within central synapses

Synapses can release multiple vesicles in response to a single action potential. This multi-vesicular release (MVR) occurs at most synapses but its spatiotemporal properties and relation to uni-vesicular release (UVR) are poorly understood. Nanoscale-resolution detection of individual release events in hippocampal boutons revealed a pattern of spatial organization of MVR, which preferentially overlapped with UVR at more central release sites. Pairs of fusion events comprising MVR were also not perfectly synchronized and the earlier event within the pair occurred closer to the active zone (AZ) center. Parallel to this organization, individual release sites had a gradient of release probability extending from the AZ center to periphery. This gradient, and spatial features of MVR, were similarly tightened by buffering intracellular calcium. These observations revealed a heterogeneous landscape of release site properties within individual AZs, which determines the spatiotemporal features of MVR and is controlled by non-uniform calcium elevation across the AZ.

neuroscience↗