Biology subjects

Sukumar, P.

Publications and source records attributed to Sukumar, P..

5 recordsLinked to original sources

bioRxiv2024

Structural insights into Pseudomonas aeruginosa lysine-specific uptake mechanism for extremely low pH regulation

Under conditions of extremely low pH, in addition to transporting lysine, bacterial lysine-specific permease (LysP) interacts with the transcriptional regulator CadC to upregulate cadBA operon expression. cadBA encodes CadA, which decarboxylates lysine to cadaverine, and CadB, which exports cadaverine to the environment to reduce acidity. This process is crucial for survival of pathogenic bacteria in their hosts. Here, we report the inward-occluded (3.2 - 5.3 [A]) cryo-EM structure of Pseudomonas aeruginosa LysP bound to L-lysine and in complex with a nanobody. L-lysine is coordinated by hydrophobic stacking, cation-{pi} interactions and hydrogen bonding mostly with polar uncharged LysP residues. LysP reconstituted into liposomes showed robust and specific transport of L-lysine with the transport being inhibited by L-4-thialysine (S-2-aminoethyl-L-cysteine). These findings inform our understanding of the specific recognition, inhibition, and transport mechanism of L-lysine by LysP, which will have important ramifications for the design of antibiotics to target bacterial LysP.

biochemistry↗

bioRxiv2023

PIEZO1 force sensing controls global lipid homeostasis

How cardiovascular activity beneficially regulates lipid homeostasis is unclear. Here we hypothesise a mechanism in which mechanical force sensed by PIEZO1 ion channels in endothelium links blood flow to lipid regulation. We engineered mice for conditional deletion of PIEZO1 in endothelium and determined consequences for lipid regulation. Prominent are upregulated expression of hepatic Cyp7a1 and intestinal Ldlr genes, which are pivotal in cholesterol catabolism and excretion. Consistent with such regulation is endothelial PIEZO1-dependence of hepatic, intestinal and whole body cholesterol and bile homeostasis. There is organ perfusion-dependent gene regulation via endothelial PIEZO1 and downstream nitric oxide synthase. Endothelial PIEZO1-deleted mice are protected against hyperlipidaemia and ectopic fat deposition. Human PIEZO1 gene variants and a recapitulated human PIEZO1 gain-of-function variant in mice associate with dyslipidaemia. The data suggest lipid-promoting effects of endothelial force sensing and new opportunity for understanding and addressing problems of hyperlipidaemia.

physiology↗

bioRxiv2021

Paracrine role for endothelial IGF-1 receptor in white adipocyte beiging

There are at least two distinct types of thermogenic adipocyte in mammals: a pre-existing form established during development, termed classical brown adipocytes and an inducible form, beige adipocytes1-3. Various environmental cues can stimulate a process frequently referred to as beiging of white adipose tissue (WAT), leading to enhanced thermogenesis and obesity resistance 4, 5. Whilst beiging of WAT as a therapeutic goal for obesity and obesity-related complications has attracted much attention6-9; therapeutics stimulating beiging without deleterious side-effects remain elusive10. The endothelium lines all blood vessels and is therefore in close proximity to all cells. Many studies support the possibility that the endothelium acts as a paracrine organ11-14. We explored the potential role of endothelial insulin-like growth factor-1 receptor (IGF-1R) as a paracrine modulator of WAT phenotype. Here we show that a reduction in endothelial IGF-1R expression in the presence of nutrient excess leads to white adipocyte beiging, increases whole-body energy expenditure and enhances insulin sensitivity via a non-cell autonomous paracrine mechanism. We demonstrate that this is mediated by endothelial release of malonic acid, which we show, using prodrug analogues, has potentially therapeutically-relevant properties in the treatment of metabolic disease.

cell biology↗

bioRxiv2020

Host auxin machinery is important in mediating root architecture changes induced by Pseudomonas fluorescens GM30 and Serendipita indica

Auxin is a key phytohormone that is integral to plant developmental processes including those underlying root initiation, elongation, and branching. Beneficial microbes have been shown to have an impact on root development, potentially mediated through auxin. In this study, we explore the role of host auxin signaling and transport components in mediating the root growth promoting effects of beneficial microbes. Towards this end, we undertook co-culture studies of Arabidopsis thaliana plants with microbes previously reported to promote lateral root proliferation and produce auxin. Two types of beneficial microbes were included in the present study; a plant growth promoting bacterial species of interest, Pseudomonas fluorescens GM30, and a well-studied plant growth promoting fungal species, Serendipita indica (Piriformospora indica). Following co-culture, lateral root production was found restored in auxin transport inhibitor-treated plants, suggesting involvement of microbe and/or microbially-produced auxin in altering plant auxin levels. In order to clarify the role of host auxin signaling and transport pathways in mediating interactions with bacterial and fungal species, we employed a suite of auxin genetic mutants as hosts in co-culture screens. Our result show that the transport proteins PIN2, PIN3, and PIN7 and the signaling protein ARF19, are required for mediating root architecture effects by the bacterial and/or fungal species. Mutants corresponding to these proteins did not significantly respond to co-culture treatment and did not show increases in lateral root production and lateral root density. These results implicate the importance of host auxin signaling in both bacterial and fungal induced changes in root architecture and serve as a driver for future research on understanding the role of auxin-dependent and auxin-independent pathways in mediating plant-microbe interactions in economically important crop species.

plant biology↗

bioRxiv2018

Piezo1 channel agonist mimics high glucose as a stimulator of insulin release

ObjectiveGlucose and hypotonicity induced cell swelling stimulate insulin release from pancreatic {beta}-cells but the mechanisms are poorly understood. Recently, Piezo1 was identified as a mechanically-activated nonselective Ca2+ permeable cationic channel in a range of mammalian cells. As cell swelling induced insulin release could be through stimulation of Ca2+ permeable stretch activated channels, we hypothesised a role for Piezo1 in cell swelling induced insulin release.\n\nMethodsTwo rat {beta}-cell lines (INS-1 and BRIN-BD11) and freshly-isolated mouse pancreatic islets were studied. Intracellular Ca2+ measurements were performed using the fura-2 Ca2+ indicator dye. Piezo1 agonist Yoda1, a competitive antagonist of Yoda1 (Dooku1) and an inactive analogue of Yoda1 (2e) were used as chemical probes. Piezo1 mRNA and insulin secretion were measured by RT-PCR and ELISA respectively.\n\nResultsPiezo1 mRNA was detected in both {beta}-cell lines and mouse islets. Yoda1 evoked Ca2+ entry which was inhibited by Yoda1 antagonist Dooku1 as well as other Piezo1 inhibitors gadolinium and ruthenium red, and not mimicked by 2e. Yoda1, but not 2e, stimulated Dooku1-sensitive insulin release from {beta}-cells and pancreatic islets. Hypotonicity and high glucose increased intracellular Ca2+ and enhanced Yoda1 Ca2+ influx responses. Pre-treatment with ruthenium red significantly reduced hypotonicity induced insulin release from {beta}-cells and pancreatic islets.\n\nConclusionThe data show that Piezo1 channel agonist induces insulin release from {beta}-cell lines and mouse pancreatic islets suggesting a role for Piezo1 in cell swelling induced insulin release. Hence Piezo1 agonists have a potential to be used as enhancers of insulin release.

cell biology↗