Biology subjects

Virdi, G.

Publications and source records attributed to Virdi, G..

4 recordsLinked to original sources

bioRxiv2024

Super-resolution imaging of proteins inside live mammalian cells with mLIVE-PAINT

Super-resolution microscopy has revolutionized biological imaging, enabling the visualization of structures at the nanometer length scale. Its application in live cells, however, has remained challenging. To address this, we adapted LIVE-PAINT, an approach we established in yeast, for application in live mammalian cells. Using the 101A/101B coiled-coil peptide pair as a peptide-based targeting system, we successfully demonstrate the super-resolution imaging of two distinct proteins in mammalian cells, one localized in the nucleus, and the second in the cytoplasm. This study highlights the versatility of LIVE-PAINT, suggesting its potential for live-cell super-resolution imaging across a range of protein targets in mammalian cells. We name the mammalian cell version of our original method mLIVE-PAINT.

synthetic biology↗

bioRxiv2024

The diversity of SNCA transcripts in neurons, and its impact on antisense oligonucleotide therapeutics

The role of the SNCA gene locus in driving Parkinsons disease (PD) through rare and common genetic variation is well-recognized, but the transcriptional diversity of SNCA in vulnerable cell types remains unclear. We performed SNCA long-read RNA sequencing in human dopaminergic neurons and show that annotated SNCA transcripts account for only 5% of expression. Rather, the majority of expression (75%) at the SNCA locus originates from transcripts with alternative 5 and 3 untranslated regions. Importantly, 10% originates from transcripts encoding open reading frames not previously annotated, which are translated and detectable in human postmortem brain. Defining the 3 untranslated regions enabled the rational design of antisense oligonucleotides targeting the majority of SNCA transcripts, leading to the effective reversal of PD pathology, including protein aggregation, mitochondrial dysfunction, and toxicity. Resolving the complexity of the SNCA transcriptional landscape impacts RNA therapies and highlights differences in protein isoforms and their contribution to disease.

neuroscience↗

bioRxiv2024

GLP-1 receptor agonism ameliorates Parkinsons disease through modulation of neuronal insulin signalling and glial suppression

Neuronal insulin resistance is linked to the pathogenesis of Parkinsons disease through unclear, but potentially targetable, mechanisms. We delineated neuronal and glial mechanisms of insulin resistance and glucagon-like 1 peptide (GLP-1) receptor agonism in human iPSC models of synucleinopathy, and corroborated our findings in patient samples from a Phase 2 trial of a GLP-1R agonist in Parkinsons (NCT01971242). Human iPSC models of synucleinopathy exhibit neuronal insulin resistance and dysfunctional insulin signalling, which is associated with inhibition of the neuroprotective Akt pathways, and increased expression of the MAPK-associated p38 and JNK stress pathways. Ultimately, this imbalance is associated with cellular stress, impaired proteostasis, accumulation of -synuclein, and neuronal loss. The GLP-1R agonist exenatide led to restoration of insulin signalling, associated with restoration of Akt signalling and suppression of the MAPK pathways in neurons. GLP-1R agonism reverses the neuronal toxicity associated with the synucleinopathy, through reduction of oxidative stress, improved mitochondrial and lysosomal function, reduced aggregation of -synuclein, and enhanced neuronal viability. GLP-1R agonism further suppresses synuclein induced inflammatory states in glia, leading to neuroprotection through non cell autonomous effects. In the exenatide-PD2 clinical trial, exenatide treatment was associated with clinical improvement in individuals with higher baseline MAPK expression (and thus insulin resistance). Exenatide treatment led to a reduction of -synuclein aggregates, and a reduction in inflammatory cytokine IL-6. Taken together, our patient platform defines the mechanisms of GLP-1R action in neurons and astrocytes, identifies the population likely to benefit from GLP-1R agonism, and highlights the utility of GLP-1R agonism as a disease modifying strategy in synucleinopathies.

neuroscience↗

bioRxiv2019

Chemerin increases T-cell mediated cytotoxicity of human tumors via modulation of a novel CMKLR1/PTEN/PD-L1 axis

Chemerin (RARRES2) is an endogenous leukocyte chemoattractant known to recruit innate immune cells through its chemotactic receptor, CMKLR1. RARRES2 is often downregulated in prostate cancer and across multiple tumor types compared to normal tissue. Additionally, a methylome-wide analysis identified RARRES2 as one of the most hypermethylated genes in sarcoma. Recent studies have shown that augmenting chemerin in the tumor microenvironment significantly suppresses tumor growth, at least in part by recruitment of immune effector cells. However, as tumor cells have been shown to express functional chemokine receptors that can impact their phenotype, we hypothesized that chemerin might have additional, tumor-intrinsic effects. Here, we show for the first time that human cancer cells exposed to exogenous chemerin significantly upregulate PTEN expression and activity. Additionally, chemerin-induced PTEN expression correlated with a concomitant reduction in PD-L1 mRNA and protein expression. Chemerin treatment of tumor cells led to significantly reduced tumor cell migration/invasion, as well as significantly increased cytotoxicity by T cells. siRNA knockdown of tumor expressed CMKLR1 abrogated chemerin-induced modulation of PTEN and PD-L1 expression and activity, supporting the presence of a CMKLR1/PTEN/PD-L1 signaling cascade. We then compared chemerin treatment to PD-L1 inhibition by siRNA knockdown or the antagonistic antibody atezolizumab in T cell cytotoxicity assays and surprisingly found chemerin treatment was as effective as both PD-L1 knockdown and atezolizumab treatment in mediating tumor lysis. Collectively, our data show a novel link between chemerin, PTEN and PD-L1 in human tumor lines, with functional consequences that may have a role in improving T cell-mediated immunotherapies.

cancer biology↗