SopB promotes phosphatidylinositol 3-phosphate formation on Salmonella vacuoles by recruiting Rab5 and Vps34

Salmonella colonizes a vacuolar niche in host cells during infection. Maturation of the Salmonella-containing vacuole (SCV) involves the formation of phosphatidylinositol 3-phosphate (PI(3)P) on its outer leaflet. SopB, a bacterial virulence factor with phosphoinositide phosphatase activity, was proposed to generate PI(3)P by dephosphorylating PI(3,4)P2, PI(3,5)P2, and PI(3,4,5)P3. Here, we examine the mechanism of PI(3)P formation during Salmonella infection. SopB is required to form PI(3,4)P2/PI(3,4,5)P3 at invasion ruffles and PI(3)P on nascent SCVs. However, we uncouple these events experimentally and reveal that SopB does not dephosphorylate PI(3,4)P2/PI(3,4,5)P3 to produce PI(3)P. Instead, the phosphatase activity of SopB is required for Rab5 recruitment to the SCV. Vps34, a PI3-kinase that associates with active Rab5, is responsible for PI(3)P formation on SCVs. Therefore, SopB mediates PI(3)P production on the SCV indirectly through recruitment of Rab5 and its effector Vps34. These findings reveal a link between phosphoinositide phosphatase activity and the recruitment of Rab5 to phagosomes

Retroviral expression of a kinase-defective IGF-I receptor suppresses growth and causes apoptosis of CHO and U87 cells in-vivo

BACKGROUND: Phosphatidylinositol-3,4,5-triphosphate (PtdInsP3) signaling is elevated in many tumors due to loss of the tumor suppressor PTEN, and leads to constitutive activation of Akt, a kinase involved in cell survival. Reintroduction of PTEN in cells suppresses transformation and tumorigenicity. While this approach works in-vitro, it may prove difficult to achieve in-vivo. In this study, we investigated whether inhibition of growth factor signaling would have the same effect as re-expression of PTEN. METHODS: Dominant negative IGF-I receptors were expressed in CHO and U87 cells by retroviral infection. Cell proliferation, transformation and tumor formation in athymic nude mice were assessed. RESULTS: Inhibition of IGF-IR signaling in a CHO cell model system by expression of a kinase-defective IGF-IR impairs proliferation, transformation and tumor growth. Reduction in tumor growth is associated with an increase in apoptosis in-vivo. The dominant-negative IGF-IRs also prevented growth of U87 PTEN-negative glioblastoma cells when injected into nude mice. Injection of an IGF-IR blocking antibody αIR3 into mice harboring parental U87 tumors inhibits tumor growth and increases apoptosis. CONCLUSION: Inhibition of an upstream growth factor signal prevents tumor growth of the U87 PTEN-deficient glioma to the same extent as re-introduction of PTEN. This result suggests that growth factor receptor inhibition may be an effective alternative therapy for PTEN-deficient tumors

Early and extended erythropoietin monotherapy after hypoxic ischaemic encephalopathy:a multicentre double-blind pilot randomised controlled trial

Objective: To examine the feasibility of early and extended erythropoietin monotherapy after hypoxic ischaemic encephalopathy (HIE). Design: Double-blind pilot randomised controlled trial.Setting: Eight neonatal units in South Asia. Patients: Neonates (≥36 weeks) with moderate or severe HIE admitted between 31 December 2022 and 3 May 2023. Interventions: Erythropoietin (500 U/kg daily) or to the placebo (sham injections using a screen) within 6 hours of birth and continued for 9 days. MRI at 2 weeks of age. Main outcomes and measures: Feasibility of randomisation, drug administration and assessment of brain injury using MRI. Results: Of the 154 neonates screened, 56 were eligible; 6 declined consent and 50 were recruited; 43 (86%) were inborn. Mean (SD) age at first dose was 4.4 (1.2) hours in erythropoietin and 4.1 (1.0) hours in placebo. Overall mortality at hospital discharge occurred in 5 (19%) vs 11 (46%) (p=0.06), and 3 (13%) vs 9 (40.9%) (p=0.04) among those with moderate encephalopathy in the erythropoietin and placebo groups. Moderate or severe injury to basal ganglia, white matter and cortex occurred in 5 (25%) vs 5 (38.5%); 14 (70%) vs 11 (85%); and 6 (30%) vs 2 (15.4%) in the erythropoietin and placebo group, respectively. Sinus venous thrombosis was seen in two (10%) neonates in the erythropoietin group and none in the control group. Conclusions: Brain injury and mortality after moderate or severe HIE are high in South Asia. Evaluation of erythropoietin monotherapy using MRI to examine treatment effects is feasible in these settings. Trial registration number: NCT05395195

Prodrug Strategy for PSMA-targeted Delivery of TGX-221 to Prostate Cancer Cells

TGX-221 is a potent, selective, and cell membrane permeable inhibitor of the PI3K p110β catalytic subunit. Recent studies showed that TGX-221 has anti-proliferative activity against PTEN-deficient tumor cell lines including prostate cancers. The objective of this study was to develop an encapsulation system for parenterally delivering TGX-221 to the target tissue through a prostate-specific membrane aptamer (PSMAa10) with little or no side effects. In this study, PEG-PCL micelles were formulated to encapsulate the drug, and a prodrug strategy was pursued to improve the stability of the carrier system. Fluorescence imaging studies demonstrated that the cellular uptake of both drug and nanoparticles were significantly improved by targeted micelles in a PSMA positive cell line. The area under the plasma concentration time curve of the micelle formulation in nude mice was 2.27-fold greater than the naked drug, and the drug clearance rate was 17.5-fold slower. These findings suggest a novel formulation approach for improving site-specific drug delivery of a molecular-targeted prostate cancer treatment

A Comparison of Mathematical Models for Polarization of Single Eukaryotic Cells in Response to Guided Cues

Polarization, a primary step in the response of an individual eukaryotic cell to a spatial stimulus, has attracted numerous theoretical treatments complementing experimental studies in a variety of cell types. While the phenomenon itself is universal, details differ across cell types, and across classes of models that have been proposed. Most models address how symmetry breaking leads to polarization, some in abstract settings, others based on specific biochemistry. Here, we compare polarization in response to a stimulus (e.g., a chemoattractant) in cells typically used in experiments (yeast, amoebae, leukocytes, keratocytes, fibroblasts, and neurons), and, in parallel, responses of several prototypical models to typical stimulation protocols. We find that the diversity of cell behaviors is reflected by a diversity of models, and that some, but not all models, can account for amplification of stimulus, maintenance of polarity, adaptation, sensitivity to new signals, and robustness

Signal transduction underlying the control of urinary bladder smooth muscle tone by muscarinic receptors and β-adrenoceptors

The normal physiological contraction of the urinary bladder, which is required for voiding, is predominantly mediated by muscarinic receptors, primarily the M3 subtype, with the M2 subtype providing a secondary backup role. Bladder relaxation, which is required for urine storage, is mediated by β-adrenoceptors, in most species involving a strong β3-component. An excessive stimulation of contraction or a reduced relaxation of the detrusor smooth muscle during the storage phase of the micturition cycle may contribute to bladder dysfunction known as the overactive bladder. Therefore, interference with the signal transduction of these receptors may be a viable approach to develop drugs for the treatment of overactive bladder. The prototypical signaling pathway of M3 receptors is activation of phospholipase C (PLC), and this pathway is also activated in the bladder. Nevertheless, PLC apparently contributes only in a very minor way to bladder contraction. Rather, muscarinic-receptor-mediated bladder contraction involves voltage-operated Ca2+ channels and Rho kinase. The prototypical signaling pathway of β-adrenoceptors is an activation of adenylyl cyclase with the subsequent formation of cAMP. Nevertheless, cAMP apparently contributes in a minor way only to β-adrenoceptor-mediated bladder relaxation. BKCa channels may play a greater role in β-adrenoceptor-mediated bladder relaxation. We conclude that apart from muscarinic receptor antagonists and β-adrenoceptor agonists, inhibitors of Rho kinase and activators of BKCa channels may have potential to treat an overactive bladder

Randomized factorial trial of esomeprazole and aspirin in Barrett’s oesophagus: the Aspirin and Esomeprazole Chemoprevention in Barrett’s metaplasia Trial (AspECT)

Background: Oesophageal adenocarcinoma (OA) is the sixth commonest cause of cancer death worldwide and Barrett’s oesophagus (BO) is the most significant risk factor. We evaluated the efficacy of high-dose esomeprazole proton pump inhibitor acid suppression (PPI) and aspirin in improving outcome for BO patients in the largest such randomized controlled trial. Methods: Patients with ≥1cm BO in UK and Canadian hospitals were randomized 1:1:1:1 using a computer-generated schedule held in a central trials unit in a 2X2 factorial design to high-dose (40mg twice-daily) or low-dose (20mg once-daily) PPI, alone or with aspirin (UK: 300mg/day, Canada: 325mg/day), unblinded (reporting pathologists blinded). The primary composite endpoint was time to all-cause mortality, OA, or high-grade dysplasia, analysed using accelerated failure time modelling adjusted for minimization factors (age, BO length, intestinal metaplasia). Findings: Recruited patients (N=2557) were followed for 8·9 years (median; interquartile range 8·2–9·8), collecting 20,095 follow-up years and 99·9% of planned data. There were 313 primary events. High-dose PPI was superior to low-dose PPI (p=0·037, N=1265 (low dose), N=1270 (high dose), time ratio (TR)=1·27, 95%CI=1·01–1·58). Aspirin was not significantly better than no aspirin (p=0·068, N=1142 (no aspirin), N = 1138 (aspirin), TR=1·24, 95%CI=0·98–1·57). If patients using NSAIDs were censored at time of first use,aspirin was significantly better than no Aspirin (p=0·043, N=2,236, TR=1·29 95%CI=1·01– 1·66). Combining high-dose PPI with aspirin had the strongest effect compared with low dose PPI without aspirin (p=0·0068, TR=1·59, 95%CI=1·14–2·23). NNT for PPI and aspirin benefit is 34 and 43, respectively. Only 1·0% (28) of participants reported study-treatment related serious adverse events. Interpretation: High-dose PPI and aspirin chemoprevention therapy, especially in combination, significantly and safely improve outcome in BO patients

The phosphatidylinositol (PI)-5-phosphate 4-kinase type II enzyme controls insulin signaling by regulating PI-3,4,5-trisphosphate degradation

Phosphatidylinositol-5-phosphate (PI-5-P) is a newly identified phosphoinositide with characteristics of a signaling lipid but no known cellular function. PI-5-P levels are controlled by the type II PI-5-P 4-kinases (PIP4K IIs), a family of kinases that converts PI-5-P into phosphatidylinositol-4,5-bisphosphate (PI-4,5-P(2)). The PI-5-P pathway is an alternative route for PI-4,5-P(2) synthesis as the bulk of this lipid is generated by the canonical pathway in which phosphatidylinositol-4-phosphate (PI-4-P) is the intermediate. Here we examined the effect of activation of the PI-5-P pathway on phosphoinositide 3-kinase (PI3K) signaling by expressing PIP4K IIβ in cells that lack this enzyme. Although PIP4K II generates PI-4,5-P(2), a substrate for PI3K, expression of this enzyme reduced rather than increased phosphatidylinositol-3,4,5-trisphosphate (PI-3,4,5-P(3)) levels in cells stimulated with insulin or cells expressing activated PI3K. This reduction in PI-3,4,5-P(3) levels resulted in decreased activation of the downstream protein kinase, Akt/PKB. Consistent with these results, expression of IpgD, a bacterial phosphatase that converts PI-4,5-P(2) to PI-5-P, resulted in Akt activation, and this effect was partially reversed by PIP4K IIβ. PIP4K IIβ expression did not impair insulin-dependent association of PI3K with insulin receptor substrate 1 (IRS1) but abbreviated Akt activation, indicating that PIP4K II regulates PI-3,4,5-P(3) degradation rather than synthesis. These data support a model in which the PI-5-P pathway controls insulin signaling that leads to Akt activation by regulating a PI-3,4,5-P(3) phosphatase