Biology subjects

Krishnamurthy, K.

Publications and source records attributed to Krishnamurthy, K..

8 recordsLinked to original sources

bioRxiv2025

A CAR-T Cell-Based Strategy for Eliminating Pathogenic Microglia in ALS

Neurodegenerative diseases are defined by the propagation of neuroinflammation, driven in part by disease-associated microglia (DAM) that amplify inflammatory signaling and hasten neurodegeneration. Strategies to selectively eliminate DAM to attenuate disease progression remain elusive. Using existing datasets in combination with multiplexed immunofluorescence analysis of post-mortem ALS tissues, we identified the urokinase-type plasminogen activator receptor (uPAR) as a novel surface marker of DAM. uPAR protein is markedly elevated in IBA1/CD68 microglia within ALS-affected regions of both sporadic and familial cases, with negligible expression in unaffected areas or control tissues. These uPAR-high microglia drive neurite retraction in iPSC-derived neurons. To target these cells, we engineered 3rd-generation CAR-T cells expressing an anti-uPAR single-chain variable fragment, enabling specific recognition and elimination of uPAR-expressing microglia. Target specificity was assessed in human microglia C20 cells driven into a pathogenic state by poly(IC) or IFN{gamma} stimulation, which resulted in robust surface uPAR expression alongside phagocytic (CD68) and antigen-presenting (CD80) markers. uPAR-CAR-T cells induced antigen-dependent cytolysis of uPAR-high microglia, reducing their viability by over 80% while sparing resting microglia and neurons in a mixed culture system. These results position uPAR-directed CAR-T cells as a viable immunotherapeutic approach to selectively disrupt disease-amplifying microglial subsets and modify the trajectories of neuroinflammatory diseases. One Sentence SummaryCAR-T cells targeting uPAR selectively ablate pathogenic microglia while sparing neurons, enabling precision immunotherapy for ALS.

neuroscience↗

bioRxiv2025

Single-molecule imaging reveals activity-dependent regulation of Camk2a mRNAs at dendritic spines

AbstractPostsynaptic calcium/calmodulin-dependent protein kinase type II (CaMKII) integrates fleeting Ca2+ transients into long-term synaptic potentiation (LTP). A persistent presence of CaMKII at dendritic spines during the maintenance of LTP facilitates the prolongation of synaptic transmission. Yet, it remains unclear how the perpetuation of CaMKII, despite protein turnover, is achieved at dendritic spines. By visualizing endogenous Camk2a mRNAs at single molecule resolution using a newly developed mouse model, we identified a rapid activity-dependent localization of mRNAs to stimulated spines near the postsynaptic density (PSD) of hippocampal neurons. This spine localization was conferred by cis-acting regulatory elements termed cytoplasmic polyadenylation elements (CPEs) in Camk2a mRNA. Spine-localized Camk2a underwent on-site translation, which persisted for extended periods. These findings uncovered a novel local regulation of Camk2a mRNA, which serves to supply dendritic spines with a steady pool of highly concentrated CaMKII for maintaining long-lasting synaptic plasticity.

neuroscience↗

bioRxiv2023

Flow-field inference from neural data using deep recurrent networks

Computations involved in processes such as decision-making, working memory, and motor control are thought to emerge from the dynamics governing the collective activity of neurons in large populations. But the estimation of these dynamics remains a significant challenge. Here we introduce Flow-field Inference from Neural Data using deep Recurrent networks (FINDR), an unsupervised deep learning method that can infer low-dimensional nonlinear stochastic dynamics underlying neural population activity. Using population spike train data from frontal brain regions of rats performing an auditory decision-making task, we demonstrate that FINDR outperforms existing methods in capturing the heterogeneous responses of individual neurons. We further show that FINDR can discover interpretable low-dimensional dynamics when it is trained to disentangle task-relevant and irrelevant components of the neural population activity. Importantly, the low-dimensional nature of the learned dynamics allows for explicit visualization of flow fields and attractor structures. We suggest FINDR as a powerful method for revealing the low-dimensional task-relevant dynamics of neural populations and their associated computations.

neuroscience↗

bioRxiv2023

C9orf72 poly(PR) mediated neurodegeneration is associated with nucleolar stress

The ALS/FTD-linked intronic hexanucleotide repeat expansion in the C9orf72 gene is translated into dipeptide repeat proteins, among which poly-proline-arginine (PR) displays the most aggressive neurotoxicity in-vitro and in-vivo. PR partitions to the nucleus when expressed in neurons and other cell types. Using drosophila and primary rat cortical neurons as model systems, we show that by lessening the nuclear accumulation of PR, we can drastically reduce its neurotoxicity. PR accumulates in the nucleolus, a site of ribosome biogenesis that regulates the cell stress response. We examined the effect of nucleolar PR accumulation and its impact on nucleolar function and determined that PR caused nucleolar stress and increased levels of the transcription factor p53. Downregulating p53 levels, either genetically or by increasing its degradation, also prevented PR-mediated neurotoxic phenotypes both in in-vitro and in-vivo models. We also investigated whether PR could cause the senescence phenotype in neurons but observed none. Instead, we found induction of apoptosis via caspase-3 activation. In summary, we uncovered the central role of nucleolar dysfunction upon PR expression in the context of C9-ALS/FTD.

neuroscience↗

bioRxiv2022

KapBeta2 is a modifier of the C9orf72-linked glycine-arginine dipeptide neurotoxicity

SummaryExpanded intronic G4C2 repeats in the C9orf72 gene cause several cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). These repeats are translated through a non-AUG-dependent mechanism into five different dipeptides (DPRs), including poly-glycine-arginine (GR), which is aggregation-prone and eventually neurotoxic. Here, we report that Kap{beta}2 and GR interact, co-aggregating in primary neurons in-vitro and CNS tissue in-vivo. Importantly, this interaction improves the overall survival of neurons expressing GR. Downregulation of Kap {beta}2 is detrimental to the survival of neurons only if GR is expressed, whereas increased Kap {beta}2 levels mitigate GR-mediated neurotoxicity. notably, we did not find any changes in TDP-43 localization nor in the dynamic properties of the GR aggregates when Kap{beta}2 was over-expressed. These findings support the design of therapeutic strategies aimed at modulating Kap {beta}2 levels as a potential new avenue for contrasting neurodegeneration in C9orf72-ALS/FTD.

neuroscience↗

bioRxiv2020

Recombinant human MG53 protein preserves mitochondria integrity in cardiomyocytes during ischemia reperfusion-induced oxidative stress

Ischemic injury to the heart causes a loss of mitochondria function due to an increase in oxidative stress. MG53, also known as TRIM72, is highly expressed in striated muscle and is essential to repair damage to plasma membrane. We have shown that mg53-/- mice are more susceptible to ischemia-reperfusion injury, whereas treatment with exogenous recombinant human MG53 (rhMG53) reduces both infarct damage and restores cardiac function. This study assesses whether MG53 protects and repairs mitochondria injury after oxidative stress associated with myocardial infarction. We hypothesize that in addition to known cell membrane repair function, MG53 acts as a myokine to protect cardiomyocytes by maintaining mitochondrial function. A combination of in vivo and in vitro ischemia/reperfusion models were used to assess MG53s effect on mitochondria using biochemical assays and confocal microscopic imaging. Treatment with rhMG53 allowed cells to maintain a healthy mitochondrial membrane potential, reduced release of mitochondrial reactive oxygen species, and mitigated mitophagy. Mitochondrial localization of rhMG53 is mediated by exposure of and interaction with cardiolipin on the mitochondrial membrane. Our data demonstrates that rhMG53 protein preserves mitochondria integrity in cardiomyocytes during ischemia reperfusion-induced oxidative stress.

physiology↗

bioRxiv2017

Disorder and the neural representation of complex odors: smelling in the real world

Animals smelling in the real world use a small number of receptors to sense a vast number of natural molecular mixtures, and proceed to learn arbitrary associations between odors and valences. Here, we propose a new interpretation of how the architecture of olfactory circuits is adapted to meet these immense complementary challenges. First, the diffuse binding of receptors to many molecules compresses a vast odor space into a tiny receptor space, while preserving similarity. Next, lateral interactions \"densify\" and decorrelate the response, enhancing robustness to noise. Finally, disordered projections from the periphery to the central brain reconfigure the densely packed information into a format suitable for flexible learning of associations and valences. We test our theory empirically using data from Drosophila. Our theory suggests that the neural processing of olfactory information differs from the other senses in its fundamental use of disorder.

neuroscience↗

bioRxiv2016

Adaptive, arousal-related adjustments of perceptual biases optimize perception in a dynamic environment

Prior expectations can be used to improve perceptual judgments about ambiguous stimuli. However, little is known about if and how these improvements are maintained in dynamic environments in which the quality of appropriate priors changes from one stimulus to the next. Using a novel sound-localization task, we show that changes in stimulus predictability lead to arousal-mediated adjustments in the magnitude of prior-driven biases that optimize perceptual judgments about each stimulus. These adjustments depend on task-dependent changes in the relevance and reliability of prior expectations, which subjects update using both normative and idiosyncratic principles. The resulting variations in biases across task conditions and individuals are reflected in modulations of pupil diameter, such that larger stimulus-evoked pupil responses correspond to smaller biases. These results suggest a critical role for the arousal system in adjusting the strength of perceptual biases with respect to inferred environmental dynamics to optimize perceptual judgements.

neuroscience↗