Protocol for determination of phosphatidylinositol 3-phosphate levels and localization in Candida glabrata by confocal microscopy

Phosphatidylinositol 3-phosphate (PI3P) levels govern membrane trafficking in Candida glabrata. Here, we present a confocal imaging-based protocol for PI3P localization analysis using the GFP-FYVE (found in Fab1, YOTB, Vac1, and EEA1) fusion protein. We describe steps for cloning the FYVE domain into the GFP-containing vector backbone, transforming FYVE-GFP into C. glabrata, and preparing slides with FYVE-GFP-expressing C. glabrata cells. We then detail procedures for acquiring and analyzing images and quantifying signal data. This protocol is adaptable to subcellular localization analysis of other low-abundant lipid and protein molecules. For complete details on the use and execution of this protocol, please refer to Askari et al. (2023).1.

Phosphatidylinositol 3-phosphate regulates iron transport via PI3P-binding CgPil1 protein

Iron homeostasis, which is pivotal to virulence, is regulated by the phosphatidylinositol 3-kinase CgVps34 in the human fungal pathogen Candida glabrata. Here, we identify CgPil1 as a phosphatidylinositol 3-phosphate (PI3P)-binding protein and unveil its role in retaining the high-affinity iron transporter CgFtr1 at the plasma membrane (PM), with PI3P negatively regulating CgFtr1-CgPil1 interaction. PI3P production and its PM localization are elevated in the high-iron environment. Surplus iron also leads to intracellular distribution and vacuolar delivery of CgPil1 and CgFtr1, respectively, from the PM. Loss of CgPil1 or CgFtr1 ubiquitination at lysines 391 and 401 results in CgFtr1 trafficking to the endoplasmic reticulum and a decrease in vacuole-localized CgFtr1. The E3-ubiquitin ligase CgRsp5 interacts with CgFtr1 and forms distinct CgRsp5-CgFtr1 puncta at the PM, with high iron resulting in their internalization. Finally, PI3P controls retrograde transport of many PM proteins. Altogether, we establish PI3P as a key regulator of membrane transport in C. glabrata.

The yapsin family of aspartyl proteases regulate glucose homeostasis in Candida glabrata

Invasive candidiasis poses a major healthcare threat. The human opportunistic fungal pathogen Candida glabrata, which causes mucosal and deep-seated infections, is armed with distinct virulence attributes, including a family of 11 glycosylphosphatidylinositol-linked aspartyl proteases, CgYapsins. Here, we have profiled total membrane proteomes of the C. glabrata wildtype and 11 proteases-deficient strain, Cgyps1-11Δ, by mass spectrometry analysis and uncovered a novel role for fungal yapsins in glucose sensing and homeostasis. Furthermore, through label-free quantitative membrane proteome analysis, we showed differential abundance of 42% of identified membrane proteins, with electron transport chain and glycolysis proteins displaying lower and higher abundance in Cgyps1-11Δ cells, compared with wildtype cells, respectively. We also demonstrated elevated glucose uptake and upregulation of genes that code for the low-glucose sensor CgSnf3, transcriptional regulators CgMig1 and CgRgt1, and hexose transporter CgHxt2/10 in the Cgyps1-11Δ mutant. We further elucidated a potential underlying mechanism through genetic and transcript measurement analysis under low- and high-glucose conditions and found CgSNF3 deletion to rescue high glucose uptake and attenuated growth of the Cgyps1-11Δ mutant in YPD medium, thereby linking CgYapsins with regulation of the CgSnf3-dependent low-glucose sensing pathway. Last, high ethanol production, diminished mitochondrial membrane potential, and elevated susceptibility to oxidative phosphorylation inhibitors point toward increased fermentative and decreased respiratory metabolism in the Cgyps1-11Δ mutant. Altogether, our findings revealed new possible glucose metabolism-regulatory roles for putative cell surface-associated CgYapsins and advanced our understanding of fungal carbohydrate homeostasis mechanisms.

Thymoquinone binds and activates human salivary aldehyde dehydrogenase: Potential therapy for the mitigation of aldehyde toxicity and maintenance of oral health

Human salivary aldehyde dehydrogenase (hsALDH) is a very important anti-oxidant enzyme present in the saliva. It is involved in the detoxification of toxic aldehydes and maintenance of oral health. Reduced level of hsALDH activity is a risk factor for oral cancer development. Thymoquinone (TQ) has many pharmacological activities and health benefits. This study aimed to examine the activation of hsALDH by TQ. The effect of TQ on the activity and kinetics of hsALDH was studied. The binding of TQ with the enzyme was examined by different biophysical methods and molecular docking analysis. TQ enhanced the dehydrogenase activity of crude and purified hsALDH by 3.2 and 2.9 fold, respectively. The K_m of the purified enzyme decreased and the V_max increased. The esterase activity also increased by 1.2 fold. No significant change in the nucleophilicity of the catalytic cysteine residue was observed. TQ forms a strong complex with hsALDH without altering the secondary structures of the enzyme. It fits in the active site of ALDH3A1 close to Cys 243 and the other highly conserved amino acid residues which lead to enhancement of substrate binding affinity and catalytic efficiency of the enzyme. TQ is expected to give better protection from toxic aldehydes in the oral cavity and to reduce the risk of oral cancer development through the activation of hsALDH. Therefore, the addition of TQ in the diet and other oral formulations is expected to be beneficial for health.

IMPROVEMENT IN PHYSICAL AND MECHANICAL PROPERTIES OF IIR/CR RUBBER BLEND ORGANOCLAY NANOCOMPOSITES

The effects of organoclay loading and chloroprene rubber (CR) concentration on the cure characteristics, microstructure, and mechanical and rheological properties of isobutylene–isoprene rubber (IIR)/CR blend were investigated. Different compositions of CR (10, 20, and 40 wt%) with Cloisite15A as organo modified nanoclay (1, 3, 5, and 7 wt%) were used for blends by a two-roll mill. Samples were vulcanized at 175 °C using a hot press. The cure and scorch times and also the maximum torque of the composites increased with the incorporation of organoclay. Mechanical properties such as tensile strength, elongation at break, modulus (100%, 200%, and 300%), and resilience improved with increasing nanoclay loading. The structure of the nanocomposites was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD results of nanocomposites indicated that the intercalation of polymer chains into the clay gallery was deduced from increasing the interlayer distance of silicate layers. TEM and SEM also directly confirmed XRD results.

A Comparison of the Effect of Different Flame Retardants on the Compressive Strength and Fire Behaviour of Rigid Polyurethane Foams

The influence of fire retardants on compressive strength and fire behaviour of rigid polyurethane foams was studied. The flame retardants studied included ammonium polyphosphate, melamine cyanurate, aluminum trihydrate, borax, and expanded graphite. The Limited Oxygen Index (LOI) showed that ammonium polyphosphate was consistently the most effective fire retardant at all filler levels tested. The one notable exception was expanded graphite, which produced an LOI of 22.7% at a relatively low 3.2% filler content. In general, the cell size decreased, and compressive strength increased, as filler % was increased. One exception to this trend was borax, which led to a significant loss in compression strength of PU when it was added at the 15% level.

Liquorice consumption and salivary testosterone concentrations

Liquorice consumption has been shown to substantially reduce serum testosterone concentration. An explanation for this result was that the active component in liquorice (glycyrrhizic acid) interfered with 17 beta-hydroxysteroid deyhydrogenase, which has been shown in vitro to catalyse the conversion of androstenedione to testosterone. We twice attempted to replicate this effect of liquorice but could not. We identified differences between our methods and those of the previous study and possible statistical anomalies (including inappropriate use of statistical tests) in the earlier report.

Retrovirus-mediated expression of HUG Br1 in Crigler-Najjar syndrome type I human fibroblasts and correction of the genetic defect in Gunn rat hepatocytes

Crigler-Najjar syndrome type I (CN-I) is a congenital hepatic metabolic deficiency in bilirubin UDP-glucuronosyltransferase activity which leads to profound jaundice and death from kernicterus. UGT1, the gene locus coding for multiple glucuronosyltransferase isoforms, has been well characterized and the cDNA for the most active form, HUG Br1, has been cloned. Recent advances in liver directed gene transfer suggest that this disease could be treated through gene therapy. As an initial step to correct the genetic defect in Crigler-Najjar type I, recombinant retroviruses were used to transduce an HUG Br1 gene into hepatocytes of a rat model of CN-I and CN-I fibroblasts. The retroviral vector gagCMVBA HUG Br1 was constructed and helper-free amphotrophic virus was isolated and used to transfer bilirubin UDP-glucuronosyltransferase activity to genetically deficient cells. The efficiency of transduction as measured by Southern blot analysis of integrated proviral sequences in DNA of recipient cells ranged from 5 to 100%. HUG Br1 gene expression was documented by blot hybridization analysis of total cellular RNA, immunotransblot analysis using a rabbit polyclonal antipeptide HUG Br1 antibody, and lysate enzymatic assay of bilirubin UDP-glucuronosyltransferase activity. HUG Br1 gene transfer was definitively demonstrated by four independent modalities following HUG Br1 retroviral transduction.