Keren, I. | Search bioRxiv

bioRxiv2026

Mitochondrial pyruvate import in astrocytes links anaplerosis to seizure resistance

Astrocytes are glycolytic cells that convert a substantial fraction of glucose-derived pyruvate into lactate, a metabolite implicated in supporting neuronal energy demand and modulating excitability, plasticity and memory. This view has placed astrocytic lactate production and export at the centre of astrocyte-neuron metabolic coupling, but whether mitochondrial pyruvate utilization in astrocytes is dispensable in vivo or fulfils an essential function in the intact brain remains unknown. Here we show that adult astrocyte-specific deletion of Mpc2, encoding an obligatory mitochondrial pyruvate carrier subunit, causes motor deficits, neuronal hyperexcitability and seizure-associated lethality. Metabolic profiling revealed pyruvate diversion toward alanine as an unsuccessful compensatory bypass, together with impaired tricarboxylic acid-cycle metabolism and an imbalance in neurotransmitter-related pools, including glutamate, glutamine and {gamma}-aminobutyric acid. Thus, astrocytic mitochondrial pyruvate import is not primarily required for bioenergetic purposes but acts as a non-redundant anaplerotic gate that maintains neurotransmitter homeostasis, excitation-inhibition balance and seizure resistance in vivo.

neuroscience↗

bioRxiv2022

Arabidopsis LSH10 transcription factor interacts with the co-repressor histone deubiquitinase OTLD1 to recruit it to the target promoters

Histone ubiquitylation/deubiquitylation plays a major role in the epigenetic regulation of gene expression. In plants, OTLD1, a member of the ovarian tumor (OTU) deubiquitinase family, deubiquitylates monoubiquitylated histone 2B and represses the expression of genes involved in growth, cell expansion, and hormone signaling. Like many other histone-modifying enzymes, OTLD1 lacks the intrinsic ability to bind DNA. How OTLD1, as well as most other known plant histone deubiquitinases, is recruited specifically to the promoters of its target genes remains unknown. Here, we show that Arabidopsis transcription factor LSH10, a member of the ALOG protein family, interacts with OTLD1 in living plant cells. Loss-of-function LSH10 mutations relieve the OTLD1-promoted transcriptional repression of the target genes, resulting in their elevated expression, whereas recovery of the LSH10 function results in down-regulated transcription of the same genes. We then show that LSH10 associates directly with the target gene chromatin as well as with the specific DNA sequence motifs in the promoter regions of the target genes. Furthermore, in the absence of LSH10, the degree of H2B monoubiquitylation in the target promoter chromatin increases. Hence, our data suggest that OTLD1-LSH10 acts as a co-repressor complex, in which LSH1 recruits OTLD1 to the target gene promoters, potentially representing a general mechanism for recruitment of plant histone deubiquitinases to the target chromatin.

plant biology↗