Spatial localization of CD16a at the human NK cell ADCC lytic synapse.

Natural Killer (NK) cells utilize effector functions, including antibody-dependent cellular cytotoxicity (ADCC), for the clearance of viral infection and cellular malignancies. NK cell ADCC is mediated by FcγRIIIa (CD16a) binding to the fragment crystallizable (Fc) region of immunoglobulin G (IgG) within immune complexes on a target cell surface. While antibody-induced clustering of CD16a is thought to drive ADCC, the molecular basis for this activity has not been fully described. Here we use MINFLUX nanoscopy to map the spatial distribution of stoichiometrically labeled CD16a across the NK cell membrane, revealing the presence of pairs of CD16a molecules with intra-doublet distance of approximately 17 nm. NK cells activated on supported lipid bilayers by Trastuzumab results in an increase of synaptic regions with greater CD16a density. Our results provide the highest spatial resolution yet described for CD16a imaging, offering new insight into how CD16a organization within the immune synapse could influence ADCC activity. MINFLUX holds great promise to further unravel the molecular details driving CD16a-based activation of NK cells.

Dapagliflozin Use in Children with Advanced Heart Failure Undergoing Heart Transplantation: A Matched Case-Control Study.

Dapagliflozin has been associated with euglycemic ketoacidosis in adults with diabetes contributing to poor outcomes when continued prior to surgery. It is unknown if preoperative use of dapagliflozin may lead to adverse events (AE) in nondiabetic children with advanced heart failure (HF) undergoing heart transplantation (HTx). We performed a single-center, matched case-control analysis of nondiabetic primary pediatric HTx recipients < 21 years-old who underwent HTx and followed through postoperative day (POD) 3. Cases who received dapagliflozin leading up to HTx (n = 22) were matched by age and cardiac diagnosis to two historical controls who did not receive dapagliflozin (n = 44). Median age at HTx was 13.8 years (range 0.36-20.7) and 48% were female. Cardiac diagnoses included cardiomyopathy (45%), Fontan failure (41%), and single ventricle status post stage I palliation (14%). Cases received median dapagliflozin dose of 0.17 mg/kg once daily; therapy was stopped one day prior to HTx. There were no significant differences in blood glucose nadirs, arterial blood gas indices including nadirs of pH, bicarbonate, or peaks of arterial blood lactic acid POD0-3. Vasopressor, inotrope, and insulin infusion usage were not different. No patients were treated for severe hypoglycemia, euglycemic ketoacidosis, or urinary tract infections. There were no deaths. Length of stay in ICU and time from HTx to hospital discharge did not differ between cohorts. Use of dapagliflozin in children with advanced HF until HTx is not associated with AE in the immediate postoperative period nor increased length of hospitalization post-HTx. Potential cardiovascular benefits of dapagliflozin in patients awaiting HTx should be prioritized.

Functional and morphological adaptation of medial prefrontal corticotropin releasing factor receptor 1-expressing neurons in male mice following chronic ethanol exposure.

Chronic ethanol dependence and withdrawal activate corticotropin releasing factor (CRF)-containing GABAergic neurons in the medial prefrontal cortex (mPFC), which tightly regulate glutamatergic pyramidal neurons. Using male CRF1:GFP reporter mice, we recently reported that CRF1-expressing (mPFCCRF1+) neurons predominantly comprise mPFC prelimbic layer 2/3 pyramidal neurons, undergo profound adaptations following chronic ethanol exposure, and regulate anxiety and conditioned rewarding effects of ethanol. To explore the effects of acute and chronic ethanol exposure on glutamate transmission, the impact of chronic alcohol on spine density and morphology, as well as persistent changes in dendritic-related gene expression, we employed whole-cell patch-clamp electrophysiology, diOlistic labeling for dendritic spine analysis, and dendritic gene expression analysis to further characterize mPFCCRF1+ and mPFCCRF1- prelimbic layer 2/3 pyramidal neurons. We found increased glutamate release in mPFCCRF1+ neurons with ethanol dependence, which recovered following withdrawal. In contrast, we did not observe significant changes in glutamate transmission in neighboring mPFCCRF1- neurons. Acute application of 44 mM ethanol significantly reduced glutamate release onto mPFCCRF1+ neurons, which was observed across all treatment groups. However, this sensitivity to acute ethanol was only evident in mPFCCRF1- neurons during withdrawal. In line with alterations in glutamate transmission, we observed a decrease in total spine density in mPFCCRF1+ neurons during dependence, which recovered following withdrawal, while again no changes were observed in mPFCCRF- neurons. Given the observed decreases in mPFCCRF1+ stubby spines during withdrawal, we then identified persistent changes at the dendritic gene expression level in mPFCCRF1+ neurons following withdrawal that may underlie these structural adaptations. Together, these findings highlight the varying responses of mPFCCRF1+ and mPFCCRF1- cell-types to acute and chronic ethanol exposure, as well as withdrawal, revealing specific functional, morphological, and molecular adaptations that may underlie vulnerability to ethanol and the lasting effects of ethanol dependence.

Prevalence of iron deficiency and anemia in pediatric heart transplant recipients.

INTRODUCTION: The prevalence of iron deficiency and anemia in the setting of modern-day maintenance immunosuppression in pediatric heart transplant (HTx) recipients is unclear. The primary aim was to determine the prevalence of iron deficiency (serum ferritin < 30 ng/mL ± transferrin saturation < 20%) and anemia per World Health Organization diagnostic criteria and associated risk factors. METHODS: Single-center, cross-sectional analysis of 200 consecutive pediatric HTx recipients (<21 years old) from 2005 to 2021. Data were collected at 1-year post-HTx at the time of annual protocol biopsy. RESULTS: Median age at transplant was 3 years (IQR .5-12.2). The median ferritin level was 32 ng/mL with 46% having ferritin < 30 ng/mL. Median transferrin saturation (TSAT) was 22% with 47% having TSAT < 20%. Median hemoglobin was 11 g/dL with 54% having anemia. Multivariable analysis revealed lower absolute lymphocyte count, TSAT < 20%, and estimated glomerular filtration rate <75 mL/min/1.73 m2 were independently associated with anemia. Ferritin < 30 ng/mL in isolation was not associated with anemia. Ferritin < 30 ng/mL may aid in detecting absolute iron deficiency while TSAT < 20% may be useful in identifying patients with functional iron deficiency ± anemia in pediatric HTx recipients. CONCLUSION: Iron deficiency and anemia are highly prevalent in pediatric HTx recipients. Future studies are needed to assess the impact of iron deficiency, whether with or without anemia, on clinical outcomes in pediatric HTx recipients.

Analysis of Platelet Function Testing in Children Receiving Aspirin for Antiplatelet Effects.

Aspirin (ASA) remains the most common antiplatelet agent used in children. VerifyNow Aspirin Test® (VN) assesses platelet response to ASA, with therapeutic effect defined by the manufacturer as ≤ 549 aspirin reaction units (ARU). Single-center, observational, analysis of 195 children (< 18 years-old) who underwent first VN between 2015 and 2020. Primary outcome was proportion of patients with ASA biochemical resistance (> 549 ARU). Secondary outcomes included incidence of new clinical thrombotic and bleeding events during ≤ 6 months from VN in those who received ASA monotherapy (n = 113). Median age was 1.8 years. Common indications for ASA included cardiac anomalies or dysfunction (74.8%) and ischemic stroke (22.6%). Median ASA dose before VN was 4.6 mg/kg/day. Mean VN was 471 ARU. ASA biochemical resistance was detected in 14.4% (n = 28). Of 113 patients receiving ASA monotherapy, 14 (12.4%) had a thrombotic event and 2 (1.8%) had a bleeding event. Mean VN was significantly higher at initial testing in patients experiencing thrombotic event compared to those without thrombosis (516 vs 465 ARU, [95% CI: 9.8, 92.2], p = 0.02). Multivariable analysis identified initial VN ASA result ≥ 500 ARU at initial testing as the only significant independent risk factor for thrombosis (p < 0.01). VN testing identifies ASA biochemical resistance in 14.4% of children. VN ASA ≥ 500 ARU rather than ≥ 550 ARU at initial testing was independently associated with increased odds of thrombosis. Designated cut-off of 550 ARU for detecting platelet dysfunction by ASA may need reconsideration in children.

MicroRNA-218 instructs proper assembly of hippocampal networks.

The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation by microRNAs (miRNAs) is a key aspect of this program. Indeed, deletion of neuron-enriched miRNAs induces strong developmental phenotypes, and miRNA levels are altered in patients with neurodevelopmental disorders. However, the mechanisms used by miRNAs to instruct brain development remain largely unexplored. Here, we identified miR-218 as a critical regulator of hippocampal assembly. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons (PNs) and GABAergic inhibitory interneurons (INs). Early life inhibition of miR-218 results in an adult brain with a predisposition to seizures. Changes in gene expression in the absence of miR-218 suggest that network assembly is impaired. Indeed, we find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Conditional knockout of Mir218-2 in INs, but not PNs, is sufficient to recapitulate long-term instability. Finally, de-repressing Kif21b and Syt13, two miR-218 targets, phenocopies the effects on early synchronous network activity induced by miR-218 inhibition. Taken together, the data suggest that miR-218 orchestrates formative events in PNs and INs to produce stable networks.

Direct observation of the conformational states of PIEZO1.

PIEZOs are mechanosensitive ion channels that convert force into chemoelectric signals1,2 and have essential roles in diverse physiological settings3. In vitro studies have proposed that PIEZO channels transduce mechanical force through the deformation of extensive blades of transmembrane domains emanating from a central ion-conducting pore4-8. However, little is known about how these channels interact with their native environment and which molecular movements underlie activation. Here we directly observe the conformational dynamics of the blades of individual PIEZO1 molecules in a cell using nanoscopic fluorescence imaging. Compared with previous structural models of PIEZO1, we show that the blades are significantly expanded at rest by the bending stress exerted by the plasma membrane. The degree of expansion varies dramatically along the length of the blade, where decreased binding strength between subdomains can explain increased flexibility of the distal blade. Using chemical and mechanical modulators of PIEZO1, we show that blade expansion and channel activation are correlated. Our findings begin to uncover how PIEZO1 is activated in a native environment. More generally, as we reliably detect conformational shifts of single nanometres from populations of channels, we expect that this approach will serve as a framework for the structural analysis of membrane proteins through nanoscopic imaging.

Mycophenolic acid therapeutic drug monitoring using area under the curve in pediatric heart transplant recipients.

INTRODUCTION: Pharmacokinetics of mycophenolic acid (MPA) display substantial interpatient variability, with up to 10-fold difference of exposure in individual patients under a fixed-dose regimen. MPA trough level (C0) monitoring is common in clinical practice but has not proven sufficiently informative in predicting MPA exposure or patient outcomes, especially in children. No limited sampling strategies (LSSs) have been generated from pediatric heart transplant (HTx) recipients to estimate MPA AUC. METHODS: Single-center, observational analysis of 135 de novo pediatric HTx recipients ≤21 years old who underwent MPA AUC between 2011 and 2021. RESULTS: Median age was 4 years (IQR .6-12.1). Median time from transplant to MPA AUC sampling was 15 days (IQR 11-19). MMF doses (mg or mg/day) had low, negative Pearson correlation coefficients (r) while doses adjusted for weight or body surface area had low correlation with Trapezoidal MPA AUC0-24 h (r = .3 and .383, respectively). MPA C0 had weak association (r = .451) with Trapezoidal MPA AUC0-24 h . LSS with two pharmacokinetic sampling time points at 90 (C3 ) and 360 (C5 ) min after MMF administration (estimated AUC0-24 h  = 32.82 + 4.12 × C3  + 11.53 × C5 ) showed strong correlation with Trapezoidal MPA AUC0-24 h (r = .87). CONCLUSION: MMF at fixed or weight-adjusted doses, as well as MPA trough levels, correlate poorly with MPA AUC0-24 h . We developed novel LSSs to estimate Trapezoidal MPA AUC from a large cohort of pediatric HTx recipients. Validation of our LSSs should be completed in a separate cohort of pediatric HTx recipients.

Assessment of the adverse effects of sirolimus versus everolimus in pediatric heart transplant recipients.

BACKGROUND: Literature is limited comparing adverse effects (AEs) of the proliferation signal inhibitors (PSIs) sirolimus (SRL) and everolimus (EVL) in pediatric heart transplant (HTx) recipients. METHODS: Single-center, observational cohort analysis assessing first use of SRL or EVL in pediatric HTx recipients <21 years of age with up to 2 years follow-up between 2009 and 2020. RESULTS: Eighty-seven patients were included, with 52 (59.8%) receiving EVL and 35 (40.2%) receiving SRL. Tacrolimus with PSI was the most common regimen. Intergroup comparison revealed lower baseline estimated glomerular filtration rate (eGFR) and greater increase in eGFR from baseline to 6 months and latest follow-up in SRL cohort compared to EVL cohort. There was greater increase in HDL cholesterol in SRL cohort compared to EVL cohort. Intragroup analysis revealed eGFR and HDL cholesterol increased significantly within SRL cohort, triglycerides and glycosylated hemoglobin increased in EVL cohort, and LDL cholesterol and total cholesterol increased in both cohorts (all p < .05). There were no differences in hematological indices or rates of aphthous ulcers, effusions, or infections between cohorts. Incidence of proteinuria was not significantly different among those screened within cohorts. Of those included in our analysis, one patient in SRL cohort (2.9%) and two in EVL cohort (3.8%) had PSI withdrawn due to AE. CONCLUSION: Low-dose PSIs in calcineurin inhibitor minimization regimens appear well-tolerated with low withdrawal rate secondary to AE in pediatric HTx recipients. While incidence of most AE was similar between PSI, our results suggest EVL may be associated with less favorable metabolic impact than SRL in this population.

Association Between Cytomegalovirus Serostatus, Antiviral Therapy, and Allograft Survival in Pediatric Heart Transplantation.

Background: Cytomegalovirus (CMV) is an important complication of heart transplantation and has been associated with graft loss in adults. The data in pediatric transplantation, however, is limited and conflicting. We conducted a large-scale cohort study to better characterize the relationship between CMV serostatus, CMV antiviral use, and graft survival in pediatric heart transplantation. Methods: 4,968 pediatric recipients of solitary heart transplants from the Scientific Registry of Transplant Recipients were stratified into three groups based on donor or recipient seropositivity and antiviral use: CMV seronegative (CMV-) transplants, CMV seropositive (CMV+) transplants without antiviral therapy, and CMV+ transplants with antiviral therapy. The primary endpoint was retransplantation or death. Results: CMV+ transplants without antiviral therapy experienced worse graft survival than CMV+ transplants with antiviral therapy (10-year: 57 vs 65%). CMV+ transplants with antiviral therapy experienced similar survival as CMV- transplants. Compared to CMV seronegativity, CMV seropositivity without antiviral therapy had a hazard ratio of 1.21 (1.07-1.37 95% CI, p-value = .003). Amongst CMV+ transplants, antiviral therapy had a hazard ratio of .82 (0.74-.92 95% CI, p-value < .001). During the first year after transplantation, these hazard ratios were 1.32 (1.06-1.64 95% CI, p-value .014) and .59 (.48-.73 95% CI, p-value < .001), respectively. Conclusions: CMV seropositivity is associated with an increased risk of graft loss in pediatric heart transplant recipients, which occurs early after transplantation and may be mitigated by antiviral therapy.

Fluoride in the diet of 2-years-old children.

OBJECTIVES: This study aimed to calculate the fluoride concentrations of commonly consumed foods and beverages for 2-years-old children utilizing market basket information for the US Midwest region. METHODS: Total Diet Study food lists were cross-referenced with National Health and Nutrition Examination Survey-What We Eat in America data to determine the foods and beverages to be included. Fluoride concentrations were determined using a modification of the hexamethyldisiloxane microdiffusion technique. Fluoride concentrations were summarized for each of the food categories. Daily dietary fluoride intake was estimated using a simulation analysis. RESULTS: Food and beverage fluoride concentrations varied widely, ranging from nondetectable for some oils and dairy products to more than 3.0 µgF/g food for some processed meats, fish and fruits. The estimated mean (±SD) daily dietary fluoride intake, excluding dentifrice and supplements, was 412±114 µgF/d. The estimated average ingestion for a 2-years-old weighing 12.24 kg was 0.034±0.009 mg/kg/d. A diet based on foods and beverages in the fifth percentile of fluoride intake distribution for an average child would result in 247 µgF/d or 0.020 mg/kg/d, while a diet with foods and beverages in the 95th percentile would result in a total intake of 622 µgF/d or 0.051 mg/kg/d. CONCLUSIONS: The fluoride concentrations of foods and beverages vary widely, and, if items in the 95th percentile of fluoride intake distribution are ingested, children could consume more fluoride than the recommended 0.05 mg/kg/d. Fluoride intake calculated in this study was higher than historically reported dietary levels.

FMRP Mediates Chronic Ethanol-Induced Changes in NMDA, Kv4.2, and KChIP3 Expression in the Hippocampus.

BACKGROUND: Exposure to chronic ethanol (EtOH) results in changes in the expression of proteins that regulate neuronal excitability. This study examined whether chronic EtOH alters the hippocampal expression and function of fragile X mental retardation protein (FMRP) and the role of FMRP in the modulation of chronic EtOH-induced changes in the expression of NMDA receptors and Kv4.2 channels. METHODS: For in vivo studies, C57BL/6J mice underwent a chronic intermittent EtOH (CIE) vapor exposure procedure. After CIE, hippocampal tissue was collected and subjected to immunoblot blot analysis of NMDA receptor subunits (GluN1, GluN2B), Kv4.2, and its accessory protein KChIP3. For in vitro studies, hippocampal slice cultures were exposed to 75 mM EtOH for 8 days. Following EtOH exposure, mRNAs bound to FMRP was measured. In a separate set of studies, cultures were exposed to an inhibitor of S6K1 (PF-4708671 [PF], 6 µM) in order to assess whether EtOH-induced homeostatic changes in protein expression depend upon changes in FMRP activity. RESULTS: Immunoblot blot analysis revealed increases in GluN1 and GluN2B but reductions in Kv4.2 and KChIP3. Analysis of mRNAs bound to FMRP revealed a similar bidirectional change observed as reduction of GluN2B and increase in Kv4.2 and KChIP3 mRNA transcripts. Analysis of FMRP further revealed that while chronic EtOH did not alter the expression of FMRP, it significantly increased phosphorylation of FMRP at the S499 residue that is known to critically regulate its activity. Inhibition of S6K1 prevented the chronic EtOH-induced increase in phospho-FMRP and changes in NMDA subunits, Kv4.2, and KChIP3. In contrast, PF had no effect in the absence of alcohol, indicating it was specific for the chronic EtOH-induced changes. CONCLUSIONS: These findings demonstrate that chronic EtOH exposure enhances translational control of plasticity-related proteins by FMRP, and that S6K1 and FMRP activities are required for expression of chronic EtOH-induced homeostatic plasticity at glutamatergic synapses in the hippocampus.

Cyclic Regulation of Sensory Perception by a Female Hormone Alters Behavior.

Females may display dramatically different behavior depending on their state of ovulation. This is thought to occur through sex-specific hormones acting on behavioral centers in the brain. Whether incoming sensory activity also differs across the ovulation cycle to alter behavior has not been investigated. Here, we show that female mouse vomeronasal sensory neurons (VSNs) are temporarily and specifically rendered "blind" to a subset of male-emitted pheromone ligands during diestrus yet fully detect and respond to the same ligands during estrus. VSN silencing occurs through the action of the female sex-steroid progesterone. Not all VSNs are targeted for silencing; those detecting cat ligands remain continuously active irrespective of the estrous state. We identify the signaling components that account for the capacity of progesterone to target specific subsets of male-pheromone responsive neurons for inactivation. These findings indicate that internal physiology can selectively and directly modulate sensory input to produce state-specific behavior. PAPERCLIP.

Neuroplasticity of A-type potassium channel complexes induced by chronic alcohol exposure enhances dendritic calcium transients in hippocampus.

RATIONALE: Chronic alcohol-induced cognitive impairments and maladaptive plasticity of glutamatergic synapses are well-documented. However, it is unknown if prolonged alcohol exposure affects dendritic signaling that may underlie hippocampal dysfunction in alcoholics. Back-propagation of action potentials (bAPs) into apical dendrites of hippocampal neurons provides distance-dependent signals that modulate dendritic and synaptic plasticity. The amplitude of bAPs decreases with distance from the soma that is thought to reflect an increase in the density of Kv4.2 channels toward distal dendrites. OBJECTIVE: The aim of this study was to quantify changes in hippocampal Kv4.2 channel function and expression using electrophysiology, Ca(2+) imaging, and western blot analyses in a well-characterized in vitro model of chronic alcohol exposure. RESULTS: Chronic alcohol exposure significantly decreased expression of Kv4.2 channels and KChIP3 in hippocampus. This reduction was associated with an attenuation of macroscopic A-type K(+) currents in CA1 neurons. Chronic alcohol exposure increased bAP-evoked Ca(2+) transients in the distal apical dendrites of CA1 pyramidal neurons. The enhanced bAP-evoked Ca(2+) transients induced by chronic alcohol exposure were not related to synaptic targeting of N-methyl-D-aspartate (NMDA) receptors or morphological adaptations in apical dendritic arborization. CONCLUSIONS: These data suggest that chronic alcohol-induced decreases in Kv4.2 channel function possibly mediated by a downregulation of KChIP3 drive the elevated bAP-associated Ca(2+) transients in distal apical dendrites. Alcohol-induced enhancement of bAPs may affect metaplasticity and signal integration in apical dendrites of hippocampal neurons leading to alterations in hippocampal function.

Insulin biosynthetic interaction network component, TMEM24, facilitates insulin reserve pool release.

Insulin homeostasis in pancreatic ß cells is now recognized as a critical element in the progression of obesity and type II diabetes (T2D). Proteins that interact with insulin to direct its sequential synthesis, folding, trafficking, and packaging into reserve granules in order to manage release in response to elevated glucose remain largely unknown. Using a conformation-based approach combined with mass spectrometry, we have generated the insulin biosynthetic interaction network (insulin BIN), a proteomic roadmap in the ß cell that describes the sequential interacting partners of insulin along the secretory axis. The insulin BIN revealed an abundant C2 domain-containing transmembrane protein 24 (TMEM24) that manages glucose-stimulated insulin secretion from a reserve pool of granules, a critical event impaired in patients with T2D. The identification of TMEM24 in the context of a comprehensive set of sequential insulin-binding partners provides a molecular description of the insulin secretory pathway in ß cells.

Piezo proteins are pore-forming subunits of mechanically activated channels.

Mechanotransduction has an important role in physiology. Biological processes including sensing touch and sound waves require as-yet-unidentified cation channels that detect pressure. Mouse Piezo1 (MmPiezo1) and MmPiezo2 (also called Fam38a and Fam38b, respectively) induce mechanically activated cationic currents in cells; however, it is unknown whether Piezo proteins are pore-forming ion channels or modulate ion channels. Here we show that Drosophila melanogaster Piezo (DmPiezo, also called CG8486) also induces mechanically activated currents in cells, but through channels with remarkably distinct pore properties including sensitivity to the pore blocker ruthenium red and single channel conductances. MmPiezo1 assembles as a ∼1.2-million-dalton homo-oligomer, with no evidence of other proteins in this complex. Purified MmPiezo1 reconstituted into asymmetric lipid bilayers and liposomes forms ruthenium-red-sensitive ion channels. These data demonstrate that Piezo proteins are an evolutionarily conserved ion channel family involved in mechanotransduction.

Pendrin modulates ENaC function by changing luminal HCO3-.

The epithelial Na(+) channel, ENaC, and the Cl(-)/HCO(3)(-) exchanger, pendrin, mediate NaCl absorption within the cortical collecting duct and the connecting tubule. Although pendrin and ENaC localize to different cell types, ENaC subunit abundance and activity are lower in aldosterone-treated pendrin-null mice relative to wild-type mice. Because pendrin mediates HCO(3)(-) secretion, we asked if increasing distal delivery of HCO(3)(-) through a pendrin-independent mechanism "rescues" ENaC function in pendrin-null mice. We gave aldosterone and NaHCO(3) to increase pendrin-dependent HCO(3)(-) secretion within the connecting tubule and cortical collecting duct, or gave aldosterone and NaHCO(3) plus acetazolamide to increase luminal HCO(3)(-) concentration, [HCO(3)(-)], independent of pendrin. Following treatment with aldosterone and NaHCO(3), pendrin-null mice had lower urinary pH and [HCO(3)(-)] as well as lower renal ENaC abundance and function than wild-type mice. With the addition of acetazolamide, however, acid-base balance as well as ENaC subunit abundance and function was similar in pendrin-null and wild-type mice. We explored whether [HCO(3)(-)] directly alters ENaC abundance and function in cultured mouse principal cells (mpkCCD). Amiloride-sensitive current and ENaC abundance rose with increased [HCO(3)(-)] on the apical or the basolateral side, independent of the substituting anion. However, ENaC was more sensitive to changes in [HCO(3)(-)] on the basolateral side of the monolayer. Moreover, increasing [HCO(3)(-)] on the apical and basolateral side of Xenopus kidney cells increased both ENaC channel density and channel activity. We conclude that pendrin modulates ENaC abundance and function, at least in part by increasing luminal [HCO(3)(-)] and/or pH.

Spiroindolones, a potent compound class for the treatment of malaria.

Recent reports of increased tolerance to artemisinin derivatives--the most recently adopted class of antimalarials--have prompted a need for new treatments. The spirotetrahydro-beta-carbolines, or spiroindolones, are potent drugs that kill the blood stages of Plasmodium falciparum and Plasmodium vivax clinical isolates at low nanomolar concentration. Spiroindolones rapidly inhibit protein synthesis in P. falciparum, an effect that is ablated in parasites bearing nonsynonymous mutations in the gene encoding the P-type cation-transporter ATPase4 (PfATP4). The optimized spiroindolone NITD609 shows pharmacokinetic properties compatible with once-daily oral dosing and has single-dose efficacy in a rodent malaria model.

Beta1 integrins are required for normal CNS myelination and promote AKT-dependent myelin outgrowth.

Oligodendrocytes in the central nervous system (CNS) produce myelin sheaths that insulate axons to ensure fast propagation of action potentials. beta1 integrins regulate the myelination of peripheral nerves, but their function during the myelination of axonal tracts in the CNS is unclear. Here we show that genetically modified mice lacking beta1 integrins in the CNS present a deficit in myelination but no defects in the development of the oligodendroglial lineage. Instead, in vitro data show that beta1 integrins regulate the outgrowth of myelin sheaths. Oligodendrocytes derived from mutant mice are unable to efficiently extend myelin sheets and fail to activate AKT (also known as AKT1), a kinase that is crucial for axonal ensheathment. The inhibition of PTEN, a negative regulator of AKT, or the expression of a constitutively active form of AKT restores myelin outgrowth in cultured beta1-deficient oligodendrocytes. Our data suggest that beta1 integrins play an instructive role in CNS myelination by promoting myelin wrapping in a process that depends on AKT.

Reduced ENaC protein abundance contributes to the lower blood pressure observed in pendrin-null mice.

Pendrin (encoded by Pds, Slc26a4) is a Cl(-)/HCO(3)(-) exchanger expressed in the apical regions of type B and non-A, non-B intercalated cells of kidney and mediates renal Cl(-) absorption, particularly when upregulated. Aldosterone increases blood pressure by increasing absorption of both Na(+) and Cl(-) through increased protein abundance and function of Na(+) transporters, such as the epithelial Na(+) channel (ENaC) and the Na(+)-Cl(-) cotransporter (NCC), as well as Cl(-) transporters, such as pendrin. Because aldosterone analogs do not increase blood pressure in Slc26a4(-/-) mice, we asked whether Na(+) excretion and Na(+) transporter protein abundance are altered in kidneys from these mutant mice. Thus wild-type and Slc26a4-null mice were given a NaCl-replete, a NaCl-restricted, or NaCl-replete diet and aldosterone or aldosterone analogs. Abundance of the major renal Na(+) transporters was examined with immunoblots and immunohistochemistry. Slc26a4-null mice showed an impaired ability to conserve Na(+) during dietary NaCl restriction. Under treatment conditions in which circulating aldosterone is increased, alpha-, beta-, and 85-kDa gamma-ENaC subunit protein abundances were reduced 15-35%, whereas abundance of the 70-kDa fragment of gamma-ENaC was reduced approximately 70% in Slc26a4-null relative to wild-type mice. Moreover, ENaC-dependent changes in transepithelial voltage were much lower in cortical collecting ducts from Slc26a4-null than from wild-type mice. Thus, in kidney, ENaC protein abundance and function are modulated by pendrin or through a pendrin-dependent downstream event. The reduced ENaC protein abundance and function observed in Slc26a4-null mice contribute to their lower blood pressure and reduced ability to conserve Na(+) during NaCl restriction.