Acute Liver Injury Caused by Cyclophosphamide in a Patient With Factor VIII Deficiency: A Rare Presentation

Because of the variety of drugs, herbal, and dietary supplements used in clinical practice. Drug-induced liver injury (DILI) has become an important and common cause of acute liver injury and failure. Many drugs associated with DILI have been identified, but there remains some uncertainty about others. Cyclophosphamide is a commonly used antineoplastic medication, and its association with DILI has been reported in animals and has been established in humans with the use of high-dose IV. Oral cyclophosphamide has not been clearly shown to cause acute liver injury, thus highlighting many of the unique aspects of this manuscript. Here, we report a case of cyclophosphamide-induced DILI with the aim to alert clinicians regarding this potential association.

A Structural Overview of TRPML1 and the TRPML Family

This chapter explores the existing structural and functional studies on the endo-lysosomal channel TRPML1 and its analogs TRPML2, TRPML3. These channels represent the mucolipin subfamily of the TRP channel superfamily comprising important roles in sensory physiology, ion homeostasis, and signal transduction. Since 2016, numerous structures have been determined for all three members using either cryo-EM or X-ray crystallography. These studies along with recent functional analysis have considerably strengthened our knowledge on TRPML channels and its related endo-lysosomal function. This chapter, together with relevant reports in other chapters from this handbook, provides an informative and detailed tool to study the endo-lysosomal cation channels.

Structure and mechanism of human cystine exporter cystinosin

Lysosomal amino acid efflux by proton-driven transporters is essential for lysosomal homeostasis, amino acid recycling, mTOR signaling, and maintaining lysosomal pH. To unravel the mechanisms of these transporters, we focus on cystinosin, a prototypical lysosomal amino acid transporter that exports cystine to the cytosol, where its reduction to cysteine supplies this limiting amino acid for diverse fundamental processes and controlling nutrient adaptation. Cystinosin mutations cause cystinosis, a devastating lysosomal storage disease. Here, we present structures of human cystinosin in lumen-open, cytosol-open, and cystine-bound states, which uncover the cystine recognition mechanism and capture the key conformational states of the transport cycle. Our structures, along with functional studies and double electron-electron resonance spectroscopic investigations, reveal the molecular basis for the transporter's conformational transitions and protonation switch, show conformation-dependent Ragulator-Rag complex engagement, and demonstrate an unexpected activation mechanism. These findings provide molecular insights into lysosomal amino acid efflux and a potential therapeutic strategy.

Fungal Planet description sheets: 1383-1435

Novel species of fungi described in this study include those from various countries as follows: Australia, Agaricus albofoetidus, Agaricus aureoelephanti and Agaricus parviumbrus on soil, Fusarium ramsdenii from stem cankers of Araucaria cunninghamii, Keissleriella sporoboli from stem of Sporobolus natalensis, Leptosphaerulina queenslandica and Pestalotiopsis chiaroscuro from leaves of Sporobolus natalensis, Serendipita petricolae as endophyte from roots of Eriochilus petricola, Stagonospora tauntonensis from stem of Sporobolus natalensis, Teratosphaeria carnegiei from leaves of Eucalyptus grandis × E. camaldulensis and Wongia ficherai from roots of Eragrostis curvula. Canada, Lulworthia fundyensis from intertidal wood and Newbrunswickomyces abietophilus (incl. Newbrunswickomyces gen. nov.) on buds of Abies balsamea. Czech Republic, Geosmithia funiculosa from a bark beetle gallery on Ulmus minor and Neoherpotrichiella juglandicola (incl. Neoherpotrichiella gen. nov.) from wood of Juglans regia. France, Aspergillus rouenensis and Neoacrodontium gallica (incl. Neoacrodontium gen. nov.) from bore dust of Xestobium rufovillosum feeding on Quercus wood, Endoradiciella communis (incl. Endoradiciella gen. nov.) endophytic in roots of Microthlaspi perfoliatum and Entoloma simulans on soil. India, Amanita konajensis on soil and Keithomyces indicus from soil. Israel, Microascus rothbergiorum from Stylophora pistillata. Italy, Calonarius ligusticus on soil. Netherlands, Appendopyricularia juncicola (incl. Appendopyricularia gen. nov.), Eriospora juncicola and Tetraploa juncicola on dead culms of Juncus effusus, Gonatophragmium physciae on Physcia caesia and Paracosmospora physciae (incl. Paracosmospora gen. nov.) on Physcia tenella, Myrmecridium phragmitigenum on dead culm of Phragmites australis, Neochalara lolae on stems of Pteridium aquilinum, Niesslia nieuwwulvenica on dead culm of undetermined Poaceae, Nothodevriesia narthecii (incl. Nothodevriesia gen. nov.) on dead leaves of Narthecium ossifragum and Parastenospora pini (incl. Parastenospora gen. nov.) on dead twigs of Pinus sylvestris. Norway, Verticillium bjoernoeyanum from sand grains attached to a piece of driftwood on a sandy beach. Portugal, Collybiopsis cimrmanii on the base of living Quercus ilex and amongst dead leaves of Laurus and herbs. South Africa, Paraproliferophorum hyphaenes (incl. Paraproliferophorum gen. nov.) on living leaves of Hyphaene sp. and Saccothecium widdringtoniae on twigs of Widdringtonia wallichii. Spain, Cortinarius dryosalor on soil, Cyphellophora endoradicis endophytic in roots of Microthlaspi perfoliatum, Geoglossum lauri-silvae on soil, Leptographium gemmatum from fluvial sediments, Physalacria auricularioides from a dead twig of Castanea sativa, Terfezia bertae and Tuber davidlopezii in soil. Sweden, Alpova larskersii, Inocybe alpestris and Inocybe boreogodeyi on soil. Thailand, Russula banwatchanensis, Russula purpureoviridis and Russula lilacina on soil. Ukraine, Nectriella adonidis on overwintered stems of Adonis vernalis. USA, Microcyclus jacquiniae from living leaves of Jacquinia keyensis and Penicillium neoherquei from a minute mushroom sporocarp. Morphological and culture characteristics are supported by DNA barcodes. Citation: Crous PW, Boers J, Holdom D, et al. 2022. Fungal Planet description sheets: 1383-1435. Persoonia 48: 261-371. https://doi.org/10.3767/persoonia.2022.48.08.

TMEM16F and dynamins control expansive plasma membrane reservoirs

Cells can expand their plasma membrane laterally by unfolding membrane undulations and by exocytosis. Here, we describe a third mechanism involving invaginations held shut by the membrane adapter, dynamin. Compartments open when Ca activates the lipid scramblase, TMEM16F, anionic phospholipids escape from the cytoplasmic monolayer in exchange for neutral lipids, and dynamins relax. Deletion of TMEM16F or dynamins blocks expansion, with loss of dynamin expression generating a maximally expanded basal plasma membrane state. Re-expression of dynamin2 or its GTPase-inactivated mutant, but not a lipid binding mutant, regenerates reserve compartments and rescues expansion. Dynamin2-GFP fusion proteins form punctae that rapidly dissipate from these compartments during TMEM16F activation. Newly exposed compartments extend deeply into the cytoplasm, lack numerous organellar markers, and remain closure-competent for many seconds. Without Ca, compartments open slowly when dynamins are sequestered by cytoplasmic dynamin antibodies or when scrambling is mimicked by neutralizing anionic phospholipids and supplementing neutral lipids. Activation of Ca-permeable mechanosensitive channels via cell swelling or channel agonists opens the compartments in parallel with phospholipid scrambling. Thus, dynamins and TMEM16F control large plasma membrane reserves that open in response to lateral membrane stress and Ca influx.

Atomic insights into ML-SI3 mediated human TRPML1 inhibition

Transient receptor potential mucolipin 1 (TRPML1) regulates lysosomal calcium signaling, lipid trafficking, and autophagy-related processes. This channel is regulated by phosphoinositides and the low pH environment of the lysosome, maintaining calcium levels essential for proper lysosomal function. Recently, several small molecules specifically targeting the TRPML family have been demonstrated to modulate channel activity. One of these, a synthetic antagonist ML-SI3, can prevent lysosomal calcium efflux and has been reported to block downstream TRPML1-mediated induction of autophagy. Here, we report a cryo-electron microscopy structure of human TRPML1 with ML-SI3 at 2.9-Å resolution. ML-SI3 binds to the hydrophobic cavity created by S5, S6, and PH1, the same cavity where the synthetic agonist ML-SA1 binds. Electrophysiological characterizations show that ML-SI3 can compete with ML-SA1, blocking channel activation yet does not inhibit PI(3,5)P₂-dependent activation of the channel. Consequently, this work provides molecular insight into how ML-SI3 and native lipids regulate TRPML1 activity.

Assessing the Quality and Performance of Institutional Review Boards: Levels of Initial Reviews

How well institutional review boards (IRBs) follow Common Rule criteria for levels of initial protocol review has not been systematically evaluated. We compared levels of review as determined using the Office for Human Research Protections (OHRP) human subject regulations decision charts of 313 protocols that had been approved by IRBs. There was a 97.8% agreement between 140 protocols that were reviewed by full board and the levels of review according to OHRP criteria. Likewise, there was a 93.8% agreement between 113 protocols that were reviewed using an expedited review procedure and OHRP criteria. However, there was only 75% agreement for exempt protocols. Specifically, 10 (16.7%) of the 60 exempt protocols were found to require IRB review, that is, six protocols requiring expedited review and four protocols requiring full board review. Conducting non-exempt research without prior IRB approval constitutes serious noncompliance. Our data suggest that exempt protocols need more scrutiny.

Validation for using electronic health records to identify community acquired pneumonia hospitalization among people with and without HIV

Background

Cohort studies identifying the incidence, complications and co-morbidities associated with community acquired pneumonia (CAP) are largely based on administrative datasets and rely on International Classification of Diseases (ICD) codes; however, the reliability of ICD codes for hospital admissions for CAP in people with HIV (PWH) has not been systematically assessed.

Methods

We used data from the Veterans Aging Cohort Study survey sample (N = 6824; 3410 PWH and 3414 uninfected) to validate the use of electronic health records (EHR) data to identify CAP hospitalizations when compared to chart review and to compare the performance in PWH vs. uninfected patients. We used different EHR algorithms that included a broad set of CAP ICD-9 codes, a set restricted to bacterial and viral CAP codes, and algorithms that included pharmacy data and/or other ICD-9 diagnoses frequently associated with CAP. We also compared microbiologic workup and etiologic diagnosis by HIV status among those with CAP.

Results

Five hundred forty-nine patients were identified as having an ICD-9 code compatible with a CAP diagnosis (13% of PWH and 4% of the uninfected, p < 0.01). The EHR algorithm with the best overall positive predictive value (82%) was obtained by using the restricted set of ICD-9 codes (480-487) in primary position or secondary only to selected codes as primary (HIV disease, respiratory failure, sepsis or bacteremia) with the addition of EHR pharmacy data; this algorithm yielded PPVs of 83% in PWH and 73% in uninfected (P = 0.1) groups. Adding aspiration pneumonia (ICD-9 code 507) to any of the ICD-9 code/pharmacy combinations increased the number of cases but decreased the overall PPV. Allowing COPD exacerbation in the primary position improved the PPV among the uninfected group only (to 76%). More PWH than uninfected patients underwent microbiologic evaluation or had respiratory samples submitted.

Conclusions

ICD-9 code-based algorithms perform similarly to identify CAP in PLWH and uninfected individuals. Adding antimicrobial use data and allowing as primary diagnoses ICD-9 codes frequently used in patients with CAP improved the performance of the algorithms in both groups of patients. The algorithms consistently performed better among PWH.

Testing the suitability of the ACCOM tool to measure outcomes of care for Culturally and Linguistically Diverse older people

The Australian Community Outcomes Measurement (ACCOM) uses a standardized set of instruments to measures functional, health, and social care-related quality of life (SCRQoL) among older people receiving services at home. One of its key components is the use of modified ASCOT SCT4 survey developed by The University of Kent PSSRU. This paper presents the preliminary findings of a pilot testing of ACCOM with CALD clients in South West Sydney using face to face interviews conducted by bilingual workers as a novel approach to administering the tool. The paper will argue that some of the domains in ASCOT SCT4 survey pose unique challenges for culturally diverse groups that highlight the ethnocentric nature of some of the questions. It also discusses some of the strategies the service provider used to address these concerns and be able to utilize the tool in a culturally effective manner.

Meeting the challenges of measuring outcomes of home care programs: The Australian Community Outcomes Measurement (ACCOM) tool

Measuring the impact of care delivered at home for frail older people is a complex task given many confounding variables that may impact on the ability of service providers to identify the direct impact of their programs on their clients' well-being and quality of life. The recent publication of the 2018 Wellness and Reablement Report Outcomes indicated that organizations lack formal processes to measure the impact of their programs on service users. There are therefore limited data exits on measuring outcomes and the performance of the ACCOM tool in the real world. Knowledge of a strong causal relationship between services provided and outcomes enables confidence in assuming the care provided was largely responsible for the outcome achieved. This paper will reflect on the experiences of one service provider in Brisbane, in implementing the Australian Community Care Outcomes Measurement (ACCOM) tool to measure and demonstrate the impact of their programs.

Abstract 231: Racial and Ethnic Disparities in Anticoagulant Choice for Atrial Fibrillation in the Veterans Health Administration: Results From the REACH AF Study

Background: Atrial fibrillation (AF) affects nearly 1 million patients in VA, with morbidity and mortality disproportionately affecting racial/ethnic minorities. Anticoagulation reduces stroke risk in AF, yet warfarin and direct oral anticoagulants (DOACs) are underused in minorities. We compared anticoagulant initiation by race/ethnicity for patients with AF in VA—which facilitates access to medications through a uniform drug formulary.

Methods: Using the VA Corporate Data Warehouse, we identified patients from 1/1/2014 - 12/31/2018 with an AF diagnosis and a confirmatory diagnosis ≦180 days of their index AF diagnosis. We excluded patients with an AF diagnosis or anticoagulant therapy in the 2 years prior to their index AF diagnosis, as well as those with valvular heart disease, who died within 180 days of AF diagnosis, or had missing or “other” race/ethnicity. We categorized our independent variable as non-Hispanic white (NHW), non-Hispanic black (NHB), and Hispanic. Our primary outcome was receipt of any anticoagulant ≦180 days of AF diagnosis as well as the type of anticoagulant (warfarin, DOAC) initiated. We used logistic regression to compare outcomes by race/ethnicity, adjusting for year of diagnosis, stroke risk with CHADS2VA2Sc score, renal disease, region and rurality.

Results: We identified 148,062 patients with incident AF: 8.6% were NHB, 3.4% Hispanic. Overall, NHBs (57.7%) and Hispanics (58.4%) were less likely than NHWs (61.4%) to initiate any anticoagulant therapy (p <0.01), driven by lower DOAC initiation for minorities (36.8% NHBs, 36.5% Hispanics, 43.0% NHWs; p <0.01). Compared to NHWs, the adjusted odds ratios (AORs) for receiving any anticoagulant or DOACs were significantly lower for NHBs and Hispanics (Table); in contrast, AORs for receiving warfarin were significantly higher among minorities. As DOAC initiation increased from 16.8% (2014) to 60.3% (2018), racial disparities in initiation increased from 1.7 to 9.1% for NHBs vs. NHWs and from 0.9 to 9.4% for Hispanics vs. NHWs.

Conclusions: In a national cohort of AF in VA, we identified significant racial/ethnic disparities in anticoagulant initiation, driven by growing disparities in DOAC initiation. Understanding these differences is essential to ensuring equitable AF care in the largest U.S. integrated health care system.

Hypertrophy of human embryonic stem cell-derived cardiomyocytes supported by positive feedback between Ca2+ and diacylglycerol signals

Human embryonic stem cell-derived cardiomyocytes develop pronounced hypertrophy in response to angiotensin-2, endothelin-1, and a selected mix of three fatty acids. All three of these responses are accompanied by increases in both basal cytoplasmic Ca2+ and diacylglycerol, quantified with the Ca2+ sensor Fluo-4 and a FRET-based diacylglycerol sensor expressed in these cardiomyocytes. The heart glycoside, ouabain (30 nM), and a recently developed inhibitor of diacylglycerol lipases, DO34 (1 μM), cause similar hypertrophy responses, and both responses are accompanied by equivalent increases of basal Ca2+ and diacylglycerol. These results together suggest that basal Ca2+ and diacylglycerol form a positive feedback signaling loop that promotes execution of cardiac growth programs in these human myocytes. Given that basal Ca2+ in myocytes depends strongly on the Na+ gradient, we also tested whether nanomolar ouabain concentrations might stimulate Na+/K+ pumps, as described by others, and thereby prevent hypertrophy. However, stimulatory effects of nanomolar ouabain (1.5 nM) were not verified on Na+/K+ pump currents in stem cell-derived myocytes, nor did nanomolar ouabain block hypertrophy induced by endothelin-1. Thus, low-dose ouabain is not a "protective" intervention under the conditions of these experiments in this human myocyte model. To summarize, the major aim of this study has been to characterize the progression of hypertrophy in human embryonic stem cell-derived cardiac myocytes in dependence on diacylglycerol and Na+ gradient changes, developing a case that positive feedback coupling between these mechanisms plays an important role in the initiation of hypertrophy programs.

On the existence of endocytosis driven by membrane phase separations

Large endocytic responses can occur rapidly in diverse cell types without dynamins, clathrin, or actin remodeling. Our experiments suggest that membrane phase separations are crucial with more ordered plasma membrane domains being internalized. Not only do these endocytic processes rely on coalescence of membrane domains, they are promoted by participation of membrane proteins in such domains, one important regulatory influence being palmitoylation. Membrane actin cytoskeleton in general resists membrane phase transitions, and its remodeling may play many roles. Besides membrane 'caging' and 'pinching' roles, typically ascribed to clathrin and dynamins, cytoskeleton remodeling may modify local membrane tension and buckling, as well as the presence and location of actin- and tension-free membrane patches. Endocytosis that depends on membrane phase separations becomes activated in metabolic stress and in response to Ca and PI3 kinase signaling. Internalized membrane traffics normally, and the secretory pathway eventually resupplies membrane to the plasmalemma or directs internalized membrane to other locations, including the extracellular space as exosomes. We describe here that endocytosis driven by membrane phase transitions is regulated by the same signaling mechanisms that regulate macropinocytosis, and it may play diverse roles in cells from nutrient assimilation to membrane recycling, cell migration, and the initiation of quiescent or hibernating cell states. Membrane ordering and phase separations have been shown to promote endocytosis in diverse cell types, including fibroblasts, myocytes, glial cells, and immune cells. We propose that clathrin/dynamin-independent endocytosis represents a continuum of related mechanisms with variable but universal dependence on membrane ordering and actin remodeling. This article is part of a Special Issue entitled: Molecular biophysics of membranes and membrane proteins.

Behavioural responses of fish groups exposed to a predatory threat under elevated CO2

Most of the studies dealing with the effects of ocean acidification (OA) on fish behaviour tested individuals in isolation, even when the examined species live in shoals in the wild. Here we evaluated the effects of elevated CO₂ concentrations (i.e. ∼900 μatm) on the shelter use and group cohesion of the gregarious damselfish Chromis viridis using groups of sub-adults exposed to a predatory threat. Results showed that, under predatory threat, fish reared at elevated CO₂ concentrations displayed a risky behaviour (i.e. decreased shelter use), whereas their group cohesion was unaffected. Our findings add on increasing evidence to account for social dynamics in OA experiments, as living in groups may compensate for CO₂-induced risky behaviour.

Resident Survey on Gastroenterology Training in Canada

BACKGROUND

Gastroenterology training in Canada is guided by the Royal College of Physicians and Surgeons of Canada. Resident perspectives on training and the degree of heterogeneity across training programs have not been previously surveyed.

AIM

This study aims to evaluate the current Canadian adult gastroenterology training experience from a resident perspective and provide insight into the heterogeneity among training programs.

METHOD

A survey designed by three current gastroenterology residents was distributed to trainees attending the Gastroenterology Residents-in-Training course at Canadian Digestive Diseases Week 2018. Categorical data from the survey was analyzed in table format. Other continuous data was converted to dichotomous data and analyzed in groups of small and large programs, the large program defined as greater than six trainees.

RESULTS

The overall response rate was 45 of 56 (80%), representing 13 of 14 accredited training sites. Mandatory rotations and core procedures varied widely across respondents, with only inpatient training consistent across all sites. Small programs had a higher call burden (P=0.039), but staff were more likely to be available to cover call if the resident coverage was unavailable (P=0.002). There were nonsignificant trends in small programs in the inability to take a post-call day (P=0.07) and a resident perception of being well trained (P=0.07).

CONCLUSIONS

There is heterogeneity across programs in mandatory rotations and core procedures. With the upcoming shift to competency-based medical education, it is an opportune time to re-evaluate and perhaps standardize how gastroenterology training is delivered in Canada.

TMEM16F activation by Ca2+ triggers plasma membrane expansion and directs PD-1 trafficking

TMEM16F is a Ca2+ -gated ion channel that is required for Ca2+ -activated phosphatidylserine exposure on the surface of many eukaryotic cells. TMEM16F is widely expressed and has roles in platelet activation during blood clotting, bone formation and T cell activation. By combining microscopy and patch clamp recording we demonstrate that activation of TMEM16F by Ca2+ ionophores in Jurkat T cells triggers large-scale surface membrane expansion in parallel with phospholipid scrambling. With continued ionophore application,TMEM16F-expressing cells then undergo extensive shedding of ectosomes. The T cell co-receptor PD-1 is selectively incorporated into ectosomes. This selectivity depends on its transmembrane sequence. Surprisingly, cells lacking TMEM16F not only fail to expand surface membrane in response to elevated cytoplasmic Ca2+, but instead undergo rapid massive endocytosis with PD-1 internalisation. These results establish a new role for TMEM16F as a regulator of Ca2+ activated membrane trafficking.

Imaging the dome of Santa Maria del Fiore using cosmic rays

The dome of Santa Maria del Fiore, Florence Cathedral, was built between 1420 and 1436 by architect Filippo Brunelleschi and it is now cracking under its own weight. Engineering efforts are under way to model the dome's structure and reinforce it against further deterioration. According to some scholars, Brunelleschi might have built reinforcement structures into the dome itself; however, the only known reinforcement is a wood chain 7.75 m above the springing of the Cupola. Multiple scattering muon radiography is a non-destructive imaging method that can be used to image the interior of the dome's wall and therefore ascertain the layout and status of any iron substructure in it. A demonstration measurement was performed at the Los Alamos National Laboratory on a mock-up wall to show the feasibility of the work proposed, and a lightweight and modular imaging system is currently under construction. We will discuss here the results of the demonstration measurement and the potential of the proposed technique, describe the imaging system under construction and outline the plans for the measurement.This article is part of the Theo Murphy meeting issue 'Cosmic-ray muography'.

Structural basis for PtdInsP2-mediated human TRPML1 regulation

Transient receptor potential mucolipin 1 (TRPML1), a lysosomal channel, maintains the low pH and calcium levels for lysosomal function. Several small molecules modulate TRPML1 activity. ML-SA1, a synthetic agonist, binds to the pore region and phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), a natural lipid, stimulates channel activity to a lesser extent than ML-SA1; moreover, PtdIns(4,5)P2, another natural lipid, prevents TRPML1-mediated calcium release. Notably, PtdIns(3,5)P2 and ML-SA1 cooperate further increasing calcium efflux. Here we report the structures of human TRPML1 at pH 5.0 with PtdIns(3,5)P2, PtdIns(4,5)P2, or ML-SA1 and PtdIns(3,5)P2, revealing a unique lipid-binding site. PtdIns(3,5)P2 and PtdIns(4,5)P2 bind to the extended helices of S1, S2, and S3. The phosphate group of PtdIns(3,5)P2 induces Y355 to form a π-cation interaction with R403, moving the S4-S5 linker, thus allosterically activating the channel. Our structures and electrophysiological characterizations reveal an allosteric site and provide molecular insight into how lipids regulate TRP channels.

Comparison of toxicant load from waterpipe and cigarette tobacco smoking among young adults in the USA

OBJECTIVES

To form population-level comparisons of total smoke volume, tar, carbon monoxide and nicotine consumed from waterpipe tobacco smoking (WTS) and cigarette smoking using data from a nationally representative sample of smokers and non-smokers aged 18-30 years.

METHODS

In March and April 2013, we surveyed a nationally representative sample of 3254 US young adults to assess the frequency and volume of WTS and cigarette smoking. We used Monte Carlo analyses with 5000 repetitions to estimate the proportions of toxicants originating from WTS and cigarette smoking. Analyses incorporated survey weights and used recent meta-analytic data to estimate toxicant exposures associated with WTS and cigarette smoking.

RESULTS

Compared with the additive estimates of WTS and cigarette smoking combined, 54.9% (95% CI 37.5% to 72.2%) of smoke volume was attributed to WTS. The proportions of tar attributable to WTS was 20.8% (95% CI 6.5% to 35.2%), carbon monoxide 10.3% (95% CI 3.3% to 17.3%) and nicotine 2.4% (95% CI 0.9% to 3.8%).

CONCLUSIONS

WTS accounted for over half of the tobacco smoke volume consumed among young US adult waterpipe and cigarette smokers. Toxicant exposures to tar, carbon monoxide and nicotine were lower, but still substantial, for WTS alone compared with WTS and cigarette smoking. Public health and policy interventions to reduce harm from tobacco smoking in young US adults should explicitly address WTS toxicant exposures.

The regulatory mechanism of mammalian TRPMLs revealed by cryo-EM

Transient receptor potential mucolipin (TRPML) channels are the most recently identified subfamily of TRP channels and have seen a surge of new reports revealing both structural and functional insight. In 2017, several groups published multiple conformations of TRPML channels using cryo-EM. Similar to other TRP channels, the ML subfamily consists of six transmembrane helices (S1-S6), and a pore region including S5, S6, and two pore helices (PH1 and PH2). However, these reports also reveal distinct structural characteristics of the ML subfamily. Asp residues within the luminal pore may function to control calcium/pH regulation. A synthetic agonist, ML-SA1, can bind to the pore region of TRPMLs to force a direct dilation of the lower gate. Finally, biophysical and electrophysiological characterizations reveal another natural agonist binding site in the unique domain of TRPMLs, presumably regulating the conformation of the S4-S5 linker to open the channel. This work elucidates the molecular architecture and provides insights into how multiple ligands regulate TRPMLs.

Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis

Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence.

Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.

Human TRPML1 channel structures in open and closed conformations

Transient receptor potential mucolipin 1 (TRPML1) is a Ca²⁺-releasing cation channel that mediates the calcium signalling and homeostasis of lysosomes. Mutations in TRPML1 lead to mucolipidosis type IV, a severe lysosomal storage disorder. Here we report two electron cryo-microscopy structures of full-length human TRPML1: a 3.72-Å apo structure at pH 7.0 in the closed state, and a 3.49-Å agonist-bound structure at pH 6.0 in an open state. Several aromatic and hydrophobic residues in pore helix 1, helices S5 and S6, and helix S6 of a neighbouring subunit, form a hydrophobic cavity to house the agonist, suggesting a distinct agonist-binding site from that found in TRPV1, a TRP channel from a different subfamily. The opening of TRPML1 is associated with distinct dilations of its lower gate together with a slight structural movement of pore helix 1. Our work reveals the regulatory mechanism of TRPML channels, facilitates better understanding of TRP channel activation, and provides insights into the molecular basis of mucolipidosis type IV pathogenesis.

Conservation of the oligomeric state of native VDAC1 in detergent micelles

The voltage-dependent anion-selective channel (VDAC) is an intrinsic β-barrel membrane protein located within the mitochondrial outer membrane where it serves as a pore, connecting the mitochondria to the cytosol. The high-resolution structures of both the human and murine VDACs have been resolved by X-ray diffraction and nuclear magnetic resonance spectroscopy (NMR) in 2008. However, the structural data are not completely in line with the findings that were obtained after decades of research on biochemical and functional analysis of VDAC. This discrepancy may be related to the fact that structural biology studies of membrane proteins reveal specific static conformations that may not necessarily represent the physiological state. For example, overexpression of membrane proteins in bacterial inclusion bodies or simply the extraction from the native lipid environment using harsh purification methods (i.e. chaotropic agents) can disturb the physiological conformations and the supramolecular assemblies. To address these potential issues, we have developed a method, allowing rapid one step purification of endogenous VDAC expressed in the native mitochondrial membrane without overexpression of recombinant protein or usage of harsh chaotropic extraction procedures. Using the Saccharomyces cerevisiae isoform 1 of VDAC as a model, this method yields efficient purification, preserving VDAC in a more physiological, native state following extraction from mitochondria. Single particle analysis using transmission electron microscopy (TEM) demonstrated conservation of oligomeric assembly after purification. Maintenance of the native state was evaluated using functional assessment that involves an ATP-binding assay by micro-scale thermophoresis (MST). Using this approach, we were able to determine for the first time the apparent KD for ATP of 1.2 mM.

A Logic Model for Understanding and Reducing Preventable Hospitalizations

Identifying and understanding the root causes of preventable hospitalization (PH) is important for improving health outcomes and reducing unnecessary healthcare costs. Thus far, however, the desire to address this issue has been impeded by a general lack of research on factors associated with PH. To begin to address this gap, we propose an evidence-based logic model of individual, environmental, and systemic factors related to PH. We aim to use this logic model to design public health interventions to reduce PH in the State of Rhode Island and to stimulate an industry-wide discussion of the problem and its possible solutions.

Optimization of TRPV6 Calcium Channel Inhibitors Using a 3D Ligand-Based Virtual Screening Method

Herein, we report the discovery of the first potent and selective inhibitor of TRPV6, a calcium channel overexpressed in breast and prostate cancer, and its use to test the effect of blocking TRPV6-mediated Ca(2+)-influx on cell growth. The inhibitor was discovered through a computational method, xLOS, a 3D-shape and pharmacophore similarity algorithm, a type of ligand-based virtual screening (LBVS) method described briefly here. Starting with a single weakly active seed molecule, two successive rounds of LBVS followed by optimization by chemical synthesis led to a selective molecule with 0.3 μM inhibition of TRPV6. The ability of xLOS to identify different scaffolds early in LBVS was essential to success. The xLOS method may be generally useful to develop tool compounds for poorly characterized targets.

Expression, purification, and structural insights for the human uric acid transporter, GLUT9, using the Xenopus laevis oocytes system

The urate transporter, GLUT9, is responsible for the basolateral transport of urate in the proximal tubule of human kidneys and in the placenta, playing a central role in uric acid homeostasis. GLUT9 shares the least homology with other members of the glucose transporter family, especially with the glucose transporting members GLUT1-4 and is the only member of the GLUT family to transport urate. The recently published high-resolution structure of XylE, a bacterial D-xylose transporting homologue, yields new insights into the structural foundation of this GLUT family of proteins. While this represents a huge milestone, it is unclear if human GLUT9 can benefit from this advancement through subsequent structural based targeting and mutagenesis. Little progress has been made toward understanding the mechanism of GLUT9 since its discovery in 2000. Before work can begin on resolving the mechanisms of urate transport we must determine methods to express, purify and analyze hGLUT9 using a model system adept in expressing human membrane proteins. Here, we describe the surface expression, purification and isolation of monomeric protein, and functional analysis of recombinant hGLUT9 using the Xenopus laevis oocyte system. In addition, we generated a new homology-based high-resolution model of hGLUT9 from the XylE crystal structure and utilized our purified protein to generate a low-resolution single particle reconstruction. Interestingly, we demonstrate that the functional protein extracted from the Xenopus system fits well with the homology-based model allowing us to generate the predicted urate-binding pocket and pave a path for subsequent mutagenesis and structure-function studies.

Massive palmitoylation-dependent endocytosis during reoxygenation of anoxic cardiac muscle

In fibroblasts, large Ca transients activate massive endocytosis (MEND) that involves membrane protein palmitoylation subsequent to mitochondrial permeability transition pore (PTP) openings. Here, we characterize this pathway in cardiac muscle. Myocytes with increased expression of the acyl transferase, DHHC5, have decreased Na/K pump activity. In DHHC5-deficient myocytes, Na/K pump activity and surface area/volume ratios are increased, the palmitoylated regulatory protein, phospholemman (PLM), and the cardiac Na/Ca exchanger (NCX1) show greater surface membrane localization, and MEND is inhibited in four protocols. Both electrical and optical methods demonstrate that PTP-dependent MEND occurs during reoxygenation of anoxic hearts. Post-anoxia MEND is ablated in DHHC5-deficient hearts, inhibited by cyclosporine A (CsA) and adenosine, promoted by staurosporine (STS), reduced in hearts lacking PLM, and correlates with impaired post-anoxia contractile function. Thus, the MEND pathway appears to be deleterious in severe oxidative stress but may constitutively contribute to cardiac sarcolemma turnover in dependence on metabolic stress.

DOI:http://dx.doi.org/10.7554/eLife.01295.001

Many people who survive a stroke or heart attack experience substantial tissue damage when the blood supply is restored. Much of this damage can be caused by the mitochondria inside the cells releasing a protein called cytochrome c that can cause cells to die in a process called apoptosis. The cytochrome c is released as the outer membrane of the mitochondria becomes permeable and pores called permeability transition pores open up in the inner membrane. Now Lin et al. explore if additional molecules released from the mitochondria might also initiate important cellular responses during the reoxygenation of oxygen-deprived tissue.

Lin and co-workers recently showed that the mitochondria of some cells can release a small enzyme cofactor, coenzyme A, which then promotes a cellular response called massive endocytosis. This process can cause up to 70% of the cell surface membrane to be absorbed into the interior of the cell in the form of membrane vesicles. Most forms of endocytosis involve a much smaller fraction of the cell membrane and employ a set of well-known endocytic proteins that are not involved in massive endocytosis. Now, Lin et al. investigate the role of massive endocytosis in cardiac muscle.

Electrical and optical measurements reveal that massive endocytosis occurs as cardiac cells that have been deprived of oxygen are reoxygenated. Lin et al. also find that an enzyme called DHHC5 must be present to allow endocytosis to take place during reoxygenation. DHHC5 is an enzyme that catalyzes a process called acylation – the transfer of acyl groups to proteins at the cell surface. Moreover, the deletion of DHHC5 has a beneficial impact on the performance of cardiac muscle after oxygen deprivation, which implies that molecules that inhibit protein acylation might protect the heart from damage during reoxygenation. Together, these results establish new pathological and physiological roles for the acylation, which is one of the most common biochemical modifications made to membrane proteins after they are synthesized.

DOI:http://dx.doi.org/10.7554/eLife.01295.002

Massive endocytosis triggered by surface membrane palmitoylation under mitochondrial control in BHK fibroblasts

Large Ca transients cause massive endocytosis (MEND) in BHK fibroblasts by nonclassical mechanisms. We present evidence that MEND depends on mitochondrial permeability transition pore (PTP) openings, followed by coenzyme A (CoA) release, acyl CoA synthesis, and membrane protein palmitoylation. MEND is blocked by inhibiting mitochondrial Ca uptake or PTP openings, depleting fatty acids, blocking acyl CoA synthesis, metabolizing CoA, or inhibiting palmitoylation. It is triggered by depolarizing mitochondria or promoting PTP openings. After mitochondrial MEND blockade, MEND is restored by cytoplasmic acyl CoA or CoA. MEND is blocked by siRNA knockdown of the plasmalemmal acyl transferase, DHHC5. When acyl CoA is abundant, transient H2O2 oxidative stress or PKC activation initiates MEND, but the immediate presence of H2O2 prevents MEND. The PTP inhibitor, NIM811, significantly increases plasmalemma in normally growing cells. Thus, the MEND pathway may contribute to constitutive as well as pathological plasmalemma turnover in dependence on mitochondrial stress signaling. DOI: http://dx.doi.org/10.7554/eLife.01293.001.

Quantifying the impact of NSAID-associated adverse events

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used among patients experiencing many different types of pain, including inflammatory, acute pain (eg, injury, low back pain, headache, postoperative pain), and chronic pain (eg, rheumatoid arthritis, osteoarthritis). However, both traditional NSAIDs and second-generation NSAIDs (cyclooxygenase-2 inhibitors) can lead to very expensive and serious adverse events. Gastrointestinal, cardiovascular, and renal complications associated with NSAIDs have been shown to be dose-dependent. In 2005, to help minimize these risks, the US Food and Drug Administration issued a public health advisory stating that "NSAIDs should be administered at the lowest effective dose for the shortest duration consistent with individual patient treatment goals." This article reviews the undue clinical and economic burden associated with NSAID-related serious adverse events.