Biology subjects

Singh, S. R.

Publications and source records attributed to Singh, S. R..

3 recordsLinked to original sources

bioRxiv2024

Ruxolitinib clears CRYAB p.Arg120Gly aggregates through the ubiquitin-proteasome system

RationaleProtein accumulation is a hallmark of many neurodegenerative and muscular diseases. Desmin-related (cardio-) myopathy (DRM), a well-studied model for cardiac muscle protein accumulation, is an autosomal dominant-inherited disease presenting with progressive muscle weakness, reduced quality of life, and shortened life span. To date, DRM patients are treated symptomatically and there is no causal treatment available. Independent of the genetic cause, most DRM patients display intracellular accumulation of desmin and its chaperone B-crystallin (CRYAB). We previously conducted an unbiased high-throughput screen to identify novel effectors that reduce cardiomyocyte aggregate levels and found that downregulation of Janus kinase 1 (JAK1) resulted in lower aggregate load in neonatal mouse cardiomyocytes. ObjectiveIn this study, we tested if the approved JAK inhibitor ruxolitinib ameliorates the disease phenotype in rodent and human CRYAB p.Arg120Gly DRM models. Methods and ResultsWe found that the mRNA levels of Jak1 and Stat3 were higher than any other JAK-signal transducer and activator of transcription (STAT) family members in neonatal rat ventricular myocytes (NRVMs) and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The approved JAK1/2 inhibitor ruxolitinib and the JAK1 inhibitors solcitinib, upadacitinib, and filgotinib prevented accumulation of and cleared pre-existing CRYAB p.Arg120Gly protein aggregates in NRVMs and hiPSC-CMs. Importantly, the knockdown of Jak1 and Stat3, but not Jak2 resulted in fewer aggregates. Moreover, ruxolitinib, Jak1 or Stat3 siRNA treatment enhanced the ubiquitin-proteasome system (UPS)-mediated degradation. Blocking UPS function blunted the effect of ruxolitinib or Jak1 siRNA on CRYAB p.Arg120Gly accumulation. RNAseq of NRVMs treated with Jak1 siRNA extracts revealed higher gene expression of important muscle E3 ubiquitinating enzymes. Knockdown of the E3 ligase Asb2 (Ankyrin Repeat And SOCS Box Protein 2) abolished the effect of ruxolitinib on CRYAB p.Arg120Gly aggregates. In DRM mice, phospho-STAT3 levels were markedly higher than in non-transgenic (NTG) mice with age. Ruxolitinib treatment or Jak1 knockout prevented cardiac dysfunction and reduced CRYAB p.Arg120Gly aggregate load in DRM mice. ConclusionIn this study, we uncovered the previously unknown effect of the approved drug ruxolitinib to enhance UPS-mediated degradation and prevent protein aggregates in cardiomyocytes.

pharmacology and toxicology↗

bioRxiv2022

Brief Report: Prognostic relevance of 3q amplification in squamous cell carcinoma of the lung

IntroductionAmplification of 3q is the most common genetic alteration identified in squamous cell carcinoma of the lung (LUSC) with the most frequent amplified region being 3q26-3q28. MethodsIn this analysis, we aim to describe the prognostic relevance of 3q by focusing on a minimal common region (MCR) of amplification within 3q constituted by 25 genes. We analyzed 511 cases of LUSC from The Cancer Genome Atlas (TCGA) and included 476 in the final analysis. ResultsWe identified a 25-gene MCR that was amplified in 221 (44.3%) cases and was associated with better disease specific-survival (DSS) (NR versus 9.25 years; 95% CI [5.24-NR]; log-rank p=0.011) and a progression-free interval (PFI) of 8 years (95% CI [5.1-NR]) versus 4.9 years (95% [3.5-NR]) (Log-rank p=0.020). Multivariable analysis revealed MCR amplification was associated with improved DSS and PFI. ConclusionAmplification of the 25-gene MCR within 3q was present in 44% of this cohort mainly composed of Caucasian patients with early-stage LUSC. This analysis is a strong indicator of the prognostic relevance of the 25-gene MCR within 3q. We are further evaluating its prognostic relevance in a racially diverse patient population with advanced LUSC.

genomics↗

bioRxiv2021

ACTN2 missense variant causes proteopathy in human iPSC-derived cardiomyocytes

Genetic variants in -actinin-2 (ACTN2) are associated with several forms of (cardio)myopathy. We previously reported a heterozygous missense (c.740C>T) ACTN2 gene variant, associated with hypertrophic cardiomyopathy, and characterized by an electro-mechanical phenotype in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Here, we created with CRISPR/Cas9 genetic tools two heterozygous functional knock-out hiPSC lines with a second wild-type (ACTN2wt) and missense ACTN2 (ACTN2mut) allele, respectively. We evaluated their impact on cardiomyocyte structure and function, using a combination of different technologies, including immunofluorescence and live cell imaging, RNA-seq, and mass spectrometry. This study showed that ACTN2mut present a higher percentage of multinucleation, protein aggregation, hypertrophy, myofibrillar disarray and activation of both the ubiquitin-proteasome system and the autophagy-lysosomal pathway as compared to ACTN2wt in 2D-cultured hiPSC-CMs. Furthermore, the expression of ACTN2mut was associated with a marked reduction of sarcomere-associated protein levels in 2D-cultured hiPSC-CMs and force impairment in engineered heart tissues. In conclusion, our study highlights the activation of proteolytic systems in ACTN2mut hiPSC-CMs likely to cope with ACTN2 aggregation and therefore directs towards proteopathy as an additional cellular pathology caused by this ACTN2 variant, which may contribute to human ACTN2-associated cardiomyopathies.

cell biology↗