Biology subjects

Godbole, A.

Publications and source records attributed to Godbole, A..

4 recordsLinked to original sources

bioRxiv2025

Functional Specialization of S-Adenosylmethionine Synthases Links Phosphatidylcholine to Mitochondrial Function and Stress Survival

S-adenosylmethionine (SAM), produced by SAM synthases, is critical for various cellular regulatory pathways and the synthesis of diverse metabolites. Studies have often equated the effects of knocking down one synthase with broader SAM-dependent outcomes such as histone methylation or phosphatidylcholine (PC) production. Humans and many other organisms express multiple SAM synthases. Evidence in Caenorhabditis elegans, which possesses four SAM synthase genes, suggest that the enzymatic source of SAM impacts its function. For instance, loss of sams-1 leads to enhanced heat shock survival and increased lifespan, whereas reducing sams-4 adversely affects heat stress survival. Here, we show that SAMS-1 contributes to a variety of intermediary metabolic pathways, whereas SAMS-4 is more important to generate SAM for methylation reactions. We demonstrate that loss of sams-1 exerts age-dependent effects on nuclear-encoded mitochondrial gene expression, mitochondrial metabolites, and may induce mitophagy. We propose a mechanistic model where reduced SAM from SAMS-1 acts through PC to impact mitochondria, thereby enhancing survival during heat stress.

cell biology↗

bioRxiv2023

Sida cordifolia, a medicinal plant is efficacious in models of Huntingtons disease, by reducing ER stress

Background and aimHuntingtons Disease is a severe neurodegenerative disorder caused by misfolded mutant huntingtin proteins with expanded stretches of polyglutamines aggregating and destroying cells in the nervous system. Sida cordifolia and Acorus calamus are medicinal plants used in traditional Ayurvedic medicine to treat neurological disorders. Here, we tested the effectiveness of extracts of both medicinal plants in decreasing aggregation of mutant huntingtin protein in models of Huntingtons Disease and explored the mode of action. Experimental procedureWe used two models, the nematode Caenorhabditis elegans and a transgenic mouse neuroblastoma cell line, both expressing mutant huntingtin proteins with elongated polyglutamines. We assessed the effect of Sida cordifolia and Acorus calamus on mutant huntingtin protein aggregation in both models, and additionally used the cell line for mechanistic studies to identify cellular pathways underlying the effects of treatment. Results and conclusionHere, we show that an extract of Sida cordifolia inhibits aggregation of mutant huntingtin proteins. In the C. elegans model, the extract prolonged life span and improved motility of the nematode by reducing aggregation of the mutant huntingtin protein. Acorus calamus did not exhibit these effects. In the transgenic mouse neuroblastoma cell line, the extract decreased aggregation of the mutant huntingtin protein by suppressing key pathways in the ER stress response caused by the mutant protein. Our results highlight the potential therapeutic value of Sida cordifolia and its promise as a source for novel medications. HighlightsO_LISida cordifolia extract reduces aggregates in HD model of transgenic worms C_LIO_LIReduction in aggregates leads to improved motility and longevity C_LIO_LISida cordifolia extract reduces ER stress in cells expressing mHTT protein C_LIO_LIFirst report on the pharmacology of Sida cordifolia in neurodegeneration C_LI

pharmacology and toxicology↗

bioRxiv2023

GRK specificity and beta gamma dependency determines a GPCR`s potential in biased agonism

G protein-coupled receptors (GPCRs) are mainly regulated by GPCR kinase (GRK) phosphorylation and subsequent {beta}-arrestin recruitment. Recently, it was shown that GPCRs differentially depend on GRK2/3, GRK2/3/5/6 or GRK5/6 for their regulation. The four ubiquitously expressed GRKs are classified into the cytosolic GRK2/3 and the membrane-tethered GRK5/6 subfamily. In vitro studies revealed that GRK2/3 interact with the membrane-localized G protein {beta}{gamma}-subunits. Yet, the role of this interaction as crosslink between G protein activation and {beta}-arrestin binding to GPCRs remained strongly underappreciated. Here we systematically show that the G{beta}{gamma}-GRK2/3 interaction is key for these GRKs to mediate {beta}-arrestin2 binding to Gs-, Gi- and Gq-coupled GPCRs. In our GRK2/3/5/6 knockout cells, without endogenous GRK background, the utilized GRK2/3 mutants devoid of the G{beta}{gamma} interaction site significantly diminished {beta}-arrestin2 recruitment to the beta-2 adrenergic receptor (b2AR), muscarinic M2 and M5 acetylcholine receptors (M2R, M5R). This effect was overwritten by artificially tethering GRK2/3 via a CAAX motif to the plasma membrane independently of free G{beta}{gamma}. Hence, the membrane recruitment is crucial for GRK2/3-mediated {beta}-arrestin2 binding to GPCRs, which is naturally induced via the G{beta}{gamma} interaction. This connects the {beta}-arrestin interaction for GRK2/3-regulated receptors inseparably with the associated G protein activation. We outline a theoretical framework of how GRK dependence on free G{beta}{gamma} can determine a GPCRs potential in biased agonism. Due to this inherent cellular mechanism for GRK2/3 recruitment and receptor phosphorylation, we propose that it will likely be mechanistically unattainable to create {beta}-arrestin-biased ligands for the subgroup of GRK2/3-regulated GPCRs, while GRK5/6-mediated receptor regulation is independent from G{beta}{gamma} availability. Accordingly, one should first determine the GRK specificity of a GPCR to ultimately assess the receptors potential for the development of biased ligands.

pharmacology and toxicology↗

bioRxiv2019

The Structural Basis of Indisulam-Mediated Recruitment of RBM39 to the DCAF15-DDB1-DDA1 E3 Ligase Complex

The anti-cancer agent Indisulam inhibits cell proliferation by causing degradation of RBM39, an essential mRNA splicing factor. Indisulam promotes an interaction between RBM39 and the DCAF15 E3 ligase substrate receptor leading to RBM39 ubiquitination and proteasome-mediated degradation. To delineate the precise mechanism by which Indisulam mediates DCAF15-RBM39 interaction, we solved the DCAF15-DDB1-DDA1-Indisulam-RBM39(RRM2) complex structure to 2.3 [A]. DCAF15 has a novel topology which embraces the RBM39(RRM2) domain largely via nonpolar interactions, and Indisulam binds between DCAF15 and RBM39(RRM2) and coordinates additional interactions between the two proteins. Studies with RBM39 point mutants and Indisulam analogs validated the structural model and defined the RBM39 alpha-helical degron motif. The degron is found only in RBM23 and RBM39 and only these proteins were detectably downregulated in Indisulam-treated HCT116 cells. This work further explains how Indisulam induces RBM39 degradation and defines the challenge of harnessing DCAF15 to degrade novel targets.

biophysics↗