Biology subjects

Premachandran, S.

Publications and source records attributed to Premachandran, S..

6 recordsLinked to original sources

bioRxiv2026

Nucleic acid turnover and lipid remodeling distinguish T cell activation and exhaustion states via label-free Raman spectroscopy

T cell exhaustion impairs immune control of chronic diseases including tuberculosis, HIV, malaria, and cancer. Its clinical implications are vast, predicting HIV-associated malignancy and treatment response and limiting the efficacy of cell therapies. Despite the advantages of monitoring and removing exhausted T cells, current detection methods require expensive antibody labeling, destructive workflows, or days-long functional assays. Here, we introduce Raman spectroscopy as a label-free assay for distinguishing T cell states directly from culture while preserving viability for downstream use. We achieve >97% accuracy in discriminating unstimulated, activated, and exhausted T cells across three donors and multiple hardware setups. We identify vibrational modes associated with nucleic acid turnover and lipid remodeling as key features that distinguish T cell activation and exhaustion. In heterogeneous populations, we quantify exhaustion percentage with R2= 1 and strong correlation to adenine (r= -0.91) and amide II protein (r= 0.94) vibrational modes. This work establishes vibrational fingerprinting as a direct measure of T cell exhaustion beyond surface marker expression towards scalable immune diagnostics, in-line monitoring, and selective immunopheresis.

biophysics↗

bioRxiv2026

Myeloid PINK1 represses mtDNA release and immune signaling that impacts neuronal pathology in patient-derived idiopathic PD models

Parkinsons disease (PD) is a neurodegenerative disorder marked by the development of cardinal motor deficits preceded by a protracted prodromal period of non-motor symptoms often involving the gastrointestinal (GI) tract. There is an emerging consensus that both the peripheral immune system and local neuroinflammation play key roles in the etiology of PD. We previously demonstrated a critical function for the Parkinsons related proteins PINK1 and Parkin as repressors of the innate to adaptive immune response in cultured cells and mouse models of infection. However, it remained unclear whether these processes were conserved in patient-derived models, and precisely how immune signaling may ultimately drive the death of dopaminergic neurons. Here we show that GI infection of PINK1 knockout (KO) mice triggered acute neurodegeneration which was evident early in the enteric nervous system. Treating wild type enteric or dopaminergic neurons with conditioned medium from immune-stimulated PINK1 KO macrophages was sufficient to promote neuronal disruption in both mouse and human neurons in vitro. Within immune-activated macrophages, we reveal that loss of PINK1 led to an enhanced release of mitochondrial DNA (mtDNA) within mitochondrial derived vesicles, leading to the activation of cGAS/STING pathways. These changes were seen in both mouse/human in vitro models and in PD patient-derived primary macrophages. Notably, pharmacological modulation using a PINK1 activator with high therapeutic potential attenuated pro-inflammatory profiles elicited by the mtDNA-dependent STING/NF-{kappa}B pathway in idiopathic patient-derived macrophages. Ultimately, our study lays the foundation for understanding PINK1-related peripheral macrophage mechanisms in idiopathic PD and provides a target for further development to treat the disease at early stages. Graphical abstractPINK1-related immune mechanisms of Parkinsons disease and associations with early neurodegenerative events. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/694713v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@6f6488org.highwire.dtl.DTLVardef@13139aaorg.highwire.dtl.DTLVardef@c0d4d1org.highwire.dtl.DTLVardef@1d41e25_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

A subset of human choroid plexus epithelial cells exhibit mitochondrial eccentricity and distinct expression of the pigmentation-associated enzyme TYRP1

For decades, ultrastructural evaluation of epithelial cells in diverse organ systems has demonstrated the existence of two subtypes identified by stark differences in cytoplasmic electron density - so-called light and dark epithelial cells. Choroid plexus (CP) epithelial cells are key regulators of CSF homeostasis and are one of many specialized epithelial linings that exhibit this bimodal phenotype. Despite longstanding acknowledgement, it has been difficult to assess the potential significance of adult human light and dark CP epithelial cells due to a lack of characterization beyond electron microscopy (EM). We present the first transcriptomic analysis of adult human CP epithelial cells and denote the existence of four epithelial subpopulations, one of which is defined by elevated expression of TYRP1 - a melanocyte-associated tyrosine-related protein involved in cellular pigmentation and proliferation. TYRP1-high cells also downregulate genes related to cilia function (which is consistent with observations of dark cell identity in organoids) and upregulate genes associated with pathways related to cell cycling, stress, and iron regulation. Our data provide an explanation of the molecular underpinning of adult human light and dark cell identity and serve as a resource for investigations of epithelial heterogeneity in the CP and other organs where dark cells are found.

neuroscience↗

bioRxiv2024

A rewiring of the earliest immune events leading to T-cell mediated disease following intestinal infection in a PINK1KO mouse model of Parkinsons disease

Parkinsons disease (PD) is characterized by a protracted period of non-motor symptoms, including gastrointestinal (GI) dysfunction, which can precede the development of the cardinal motor deficits by decades. This long prodrome of disease is highly suggestive of immune cell involvement in the initiation of disease, but currently the field lacks robust model systems to study such mechanisms. It has been hypothesized that pathology may be first initiated in the periphery due to environmental triggers, such as pathogens that enter the GI tract. We further speculate that the impact of such pathogens on the immune system could be exacerbated in genetically predisposed individuals. Our group has developed a GI-targeted pathogen-induced PD mouse model system in PINK1 KO mice with Gram-negative bacterial infections and found that T cells are a major player in driving PD-like motor symptoms at late stages following infection. Herein, we now map the initiating immune events at the site of infection at the earliest stages with the goal of shedding light on the earliest mechanisms triggering immune-mediated pathological processes relevant to PD. Using unbiased single cell sequencing, we demonstrate that myeloid cells are the earliest dysregulated immune cell type in PINK1 KO infected mice at 1-week post-infection, followed by a dysregulated T cell response shortly after, at 2 weeks post-infection. We find that these myeloid cells have an enhanced proinflammatory profile, are more mature, and develop enhanced capacity for antigen presentation. Using unbiased prediction analysis, our data suggest that cytotoxic T cells and myeloid cells are particularly poised for interacting with each other, and we identify possible direct cell-cell interaction pathways that might be implicated. Taken together, deciphering the earliest immune mechanisms in the periphery underpinning PD autoimmunity will be instrumental in the development of effective therapeutic targeting strategies before irrevocable neuronal damage ensues.

immunology↗

bioRxiv2023

Chronic pain mediated changes in the appetitive value of affective touch in mice

The existence of skin-to-brain circuits for rewarding gentle touch highlight its critical nature across species. However, this gentle affective touch is not always appetitive and can produce aversion or negative affect in disorders such as chronic pain. Sensory neurons expressing the protein MrgprB4 detect gentle stroking in mice and their activation of these neurons known to be positively reinforcing. Here we assess whether activation of channelrhodopsin (ChR2) expressing MrgprB4 afferents signal positively valenced tactile information and whether this is altered in models of chronic pain. We further interrogate how this this sensory information is reflected in the downstream circuits recruited. Optogenetic activation of MrgprB4 lineage afferents was found to be appetitive in control and capsaicin sensitized mice but not nerve injured mice, indicating that the appetitive value is diminished in neuropathic pain. Remarkably, this appetitive value was partially recovered in male nerve injured mice by treatment with the analgesic gabapentin. These behavioral changes were also accompanied by different patterns of neuronal activity throughout the brain, including altered activation of sites that receive direct projections from the spinal cord between sham and nerve injured mice. Together, these findings highlight the plastic nature of these affective tactile circuits under pathological conditions.

neuroscience↗

bioRxiv2023

Characterizing the diversity of enteric neurons using Dopamine Transporter (DAT)-Cre reporter mice

The enteric nervous system (ENS) comprises a complex network of neurons whereby a subset appears to be dopaminergic, although the characteristics, roles, and implications in disease are less understood. Most investigations relating to enteric dopamine (DA) neurons rely on immunoreactivity to tyrosine hydroxylase (TH) - a rate-limiting enzyme in the production of DA. However, TH immunoreactivity is likely to provide an incomplete picture given previous work has showed that some DA neurons contain little if any TH and its levels tend to be decreased in response to cellular stress. This study herein provides a comprehensive characterization of DA neurons in the gut using a well-accepted reporter mouse line, expressing a fluorescent protein (tdTomato) under control of the DA transporter (DAT) promoter. Our findings confirm a unique localization of DA neurons in the gut and unveil the discrete subtypes of DA neurons in this organ, which we characterized using both immunofluorescence and single-cell transcriptomics, as well as validated using in situ hybridization. We observed distinct subtypes of DAT-tdTomato neurons expressing co-transmitters and modulators across both plexuses; some of them likely co-releasing acetylcholine, while others were positive for a slew of canonical DA markers (TH, VMAT2 and GIRK2). Interestingly, we uncovered a seemingly novel population of DA neurons unique to the ENS which were ChAT/DAT-tdTomato-immunoreactive neurons and were characterised by the expression of Grp, Calcb and Sst. Given the clear heterogeneity of DAergic gut neurons, further investigation is warranted to define their functional signatures and discover any inherent vulnerabilities in disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/545271v3_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1e1830borg.highwire.dtl.DTLVardef@625579org.highwire.dtl.DTLVardef@1d9b59aorg.highwire.dtl.DTLVardef@219cab_HPS_FORMAT_FIGEXP M_FIG C_FIG Using a reporter mouse line, expressing a fluorescent protein under control of the dopamine transporter (DAT) promoter, discrete subtypes of dopaminergic neurons were unveiled across the ganglionated plexuses of the gut. A novel subpopulations of enteric DA neurons, expressing genes previously reported involved in dopamine signaling in the brain, exhibit a cholinergic phenotype.

neuroscience↗