Biology subjects

Lechleiter, J. D.

Publications and source records attributed to Lechleiter, J. D..

6 recordsLinked to original sources

bioRxiv2026

Calcineurin B-mediated Ca2+ sensing translates stress signal intensity into the assembly of phase-separated condensates at PERK complexes.

Endoplasmic reticulum (ER) stress activates protein kinase RNA-like ER kinase (PERK), which initially promotes adaptive responses but remains the only active UPR branch during prolonged stress, mediating both early cytoprotective and chronic pro-apoptotic signaling. Recently, we identified translocon-generated Ca2+ microdomains that promote PERK phosphorylation during early UPR, revealing a mechanism by which local Ca2+ signals regulate UPR activation. However, the molecular mechanism linking these Ca2+ microdomains to PERK activation remains elusive. Previously, we showed that calcineurin (CN), a Ca2+ -dependent heterodimer composed of catalytic (CNA) and regulatory (CNB) subunits, exerts a non-canonical pro-survival function by promoting PERK autophosphorylation. Here, using super-resolution microscopy, CRISPR-Cas9 editing, in silico analyses, and optogenetic droplet assays, we identify CNB as a local Ca2+ sensor that couples translocon-generated Ca2+ signals to liquid condensate assembly, thereby promoting adaptive PERK phosphorylation. These findings establish CNB-mediated condensate assembly as a mechanism that translates local Ca2+ signals into spatially organized early adaptive PERK signaling.

cell biology↗

bioRxiv2026

Ventral tegmental area astrocytes regulate drug-cue associations and drug intake

Cocaine use disorder remains a critical public health concern with limited treatment options. Astrocytes are increasingly recognized as active regulators of neurotransmission and are emerging as important contributors to addiction neurobiology. Here, we examined how chemogenetic activation of astrocytic Gq signaling within the ventral tegmental area (VTA) influences cocaine-associated behaviors in drug-naive and cocaine-experienced rats. Using a subthreshold dose of cocaine in a conditioned place preference (CPP) paradigm, we found that VTA astrocyte Gq activation facilitated the acquisition of cocaine CPP in drug-naive rats but suppressed the development of cocaine CPP in cocaine-experienced rats. Additionally, chemogenetic activation of VTA astrocyte Gq signaling suppressed voluntary cocaine intake in a self-administration paradigm. Together, these findings demonstrate that VTA astrocyte Gq signaling shapes cocaine-associated behaviors in a drug history-dependent manner, highlighting VTA astrocytes as a potential therapeutic target in cocaine use disorder.

neuroscience↗

bioRxiv2025

β-Hydroxybutyrate enhances brain metabolism in normoglycemia and hyperglycemia, providing cerebroprotection in a mouse stroke model.

Hyperglycemia in poorly controlled diabetes is widely recognized as detrimental to organ dysfunction. However, the acute effects of hyperglycemia on brain metabolism and function are not fully understood. The potential protective benefit of ketone bodies on mitochondrial function in the brain has also not been well characterized. Here, we evaluated the acute effects of hyperglycemia and {beta}-hydroxybutyrate (BHB) on brain metabolism by employing a novel approach leveraging adenosine triphosphate (ATP)-dependence of bioluminescence originating from luciferin-luciferase activity. Oxygen consumption rate was measured in ex vivo live brain punches to further evaluate mitochondrial function. Additionally, we investigated the functional relevance of BHB using an in vivo photothrombotic stroke model to assess its cerebroprotective effects. Our data demonstrate that brain metabolism in mice is affected by acute exposure to high glucose, at a level similar to consuming food or a beverage with high sucrose. This short-term effect of glucose exposure was reduced by co-administration with the ketone body BHB. Moreover, BHB significantly reduced infarct size in the brain stroke model, providing evidence for its functional protective role in the brain. These findings suggest that BHB may effectively mitigate the adverse effects of metabolic stress and ischemic events on brain metabolism and function.

neuroscience↗

bioRxiv2024

Quinolinic acid links kidney injury to brain toxicity

Kidney dysfunction often leads to neurological impairment, yet the complex kidney-brain relationship remains elusive. We employed spatial and bulk metabolomics to investigate a mouse model of rapid kidney failure induced by mouse double minute 2 (Mdm2) conditional deletion in the kidney tubules to interrogate kidney and brain metabolism. Pathway enrichment analysis of focused plasma metabolomics panel pinpointed tryptophan metabolism as the most altered pathway with kidney failure. Spatial metabolomics showed toxic tryptophan metabolites in the kidneys and brains, revealing a novel connection between advanced kidney disease and accelerated kynurenine degradation. In particular, the excitotoxic metabolite quinolinic acid was localized in ependymal cells adjacent to the ventricle in the setting of kidney failure. These findings were associated with brain inflammation and cell death. A separate mouse model of acute kidney injury also had an increase in circulating toxic tryptophan metabolites along with altered brain inflammation. Patients with advanced CKD similarly demonstrated elevated plasma kynurenine metabolites and quinolinic acid was uniquely correlated with fatigue and reduced quality of life in humans. Overall, our study identifies the kynurenine pathway as a bridge between kidney decline, systemic inflammation, and brain toxicity, offering potential avenues for diagnosis and treatment of neurological issues in kidney disease.

molecular biology↗

bioRxiv2022

Adenosine A1R/A3R Agonist AST-004 Reduces Brain Infarction in Mouse and Rat Models of Acute Ischemic Stroke

Acute ischemic stroke (AIS) is the second leading cause of death globally. No Food and Drug Administration (FDA) approved therapies exist targeting cerebroprotection following stroke. Our group recently reported significant cerebroprotection with the adenosine A1/A3 receptor agonist, AST-004, in a transient stroke model in non-human primates (NHP) and in a preclinical mouse model of traumatic brain injury (TBI). However, the specific receptor pathway activated was only inferred based on in vitro binding studies. The current study investigated the underlying mechanism of AST-004 cerebroprotection in two independent models of AIS: permanent photothrombotic stroke in mice and transient middle cerebral artery occlusion (MCAO) in rats. AST-004 treatments across a range of doses were cerebroprotective and efficacy could be blocked by A3R antagonism, indicating a mechanism of action that does not require A1R agonism. The high affinity A3R agonist MRS5698 was also cerebroprotective following stroke, but not the A3R agonist Cl-IB-MECA under our experimental conditions. AST-004 efficacy was blocked by the astrocyte specific mitochondrial toxin fluoroacetate, confirming an underlying mechanism of cerebroprotection dependent on astrocyte mitochondrial metabolism. An increase in A3R mRNA levels following stroke suggested an intrinsic cerebroprotective response that was mediated by A3R signaling. Together, these studies confirm certain A3R agonists, such as AST-004, are promising new therapeutics for the treatment of AIS.

neuroscience↗

bioRxiv2020

Endoplasmic reticulum stress induces a novel Ca2+ signalling system initiated by Ca2+ microdomains

The accumulation of unfolded proteins within the Endoplasmic Reticulum (ER) activates a signal transduction pathway termed the unfolded protein response (UPR), which attempts to restore ER homeostasis. If homeostasis cannot be restored, UPR signalling ultimately induces apoptosis. Ca2+ depletion in the ER is a potent inducer of ER stress. Despite the ubiquity of Ca2+ as intracellular messenger, the precise mechanism (s) by which Ca2+ release affects the UPR remains unknown. Use of a genetically encoded Ca2+ indicator (GCamP6) that is tethered to the ER membrane, uncovered novel Ca2+ signalling events initiated by Ca2+ microdomains in human astrocytes under ER stress, as well as in a cell model deficient in all three IP3 Receptor isoforms. Pharmacological and molecular studies indicate that these local events are mediated by translocons. Together, these data reveal the existence of a previously unrecognized mechanism by which stressor-mediated Ca2+ release regulates ER stress.

cell biology↗