1
|
Stewart AJ, Tuncay E, Pitt SJ, Rainbow RD. Editorial: Insulin resistance and cardiovascular disease. Front Endocrinol (Lausanne) 2023; 14:1266173. [PMID: 37600708 PMCID: PMC10436739 DOI: 10.3389/fendo.2023.1266173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 07/26/2023] [Indexed: 08/22/2023] Open
Affiliation(s)
- Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Erkan Tuncay
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Richard D. Rainbow
- Department of Cardiovascular and Metabolic Medicine & Liverpool Centre for Cardiovascular Sciences, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| |
Collapse
|
2
|
Dorward AM, Stewart AJ, Pitt SJ. The role of Zn2+ in shaping intracellular Ca2+ dynamics in the heart. J Gen Physiol 2023; 155:e202213206. [PMID: 37326614 PMCID: PMC10276528 DOI: 10.1085/jgp.202213206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/18/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
Increasing evidence suggests that Zn2+ acts as a second messenger capable of transducing extracellular stimuli into intracellular signaling events. The importance of Zn2+ as a signaling molecule in cardiovascular functioning is gaining traction. In the heart, Zn2+ plays important roles in excitation-contraction (EC) coupling, excitation-transcription coupling, and cardiac ventricular morphogenesis. Zn2+ homeostasis in cardiac tissue is tightly regulated through the action of a combination of transporters, buffers, and sensors. Zn2+ mishandling is a common feature of various cardiovascular diseases. However, the precise mechanisms controlling the intracellular distribution of Zn2+ and its variations during normal cardiac function and during pathological conditions are not fully understood. In this review, we consider the major pathways by which the concentration of intracellular Zn2+ is regulated in the heart, the role of Zn2+ in EC coupling, and discuss how Zn2+ dyshomeostasis resulting from altered expression levels and efficacy of Zn2+ regulatory proteins are key drivers in the progression of cardiac dysfunction.
Collapse
Affiliation(s)
- Amy M. Dorward
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, UK
| | | |
Collapse
|
3
|
Fritzen R, Davies A, Veenhuizen M, Campbell M, Pitt SJ, Ajjan RA, Stewart AJ. Magnesium Deficiency and Cardiometabolic Disease. Nutrients 2023; 15:nu15102355. [PMID: 37242238 DOI: 10.3390/nu15102355] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/12/2023] [Accepted: 05/13/2023] [Indexed: 05/28/2023] Open
Abstract
Magnesium (Mg2+) has many physiological functions within the body. These include important roles in maintaining cardiovascular functioning, where it contributes to the regulation of cardiac excitation-contraction coupling, endothelial functioning and haemostasis. The haemostatic roles of Mg2+ impact upon both the protein and cellular arms of coagulation. In this review, we examine how Mg2+ homeostasis is maintained within the body and highlight the various molecular roles attributed to Mg2+ in the cardiovascular system. In addition, we describe how nutritional and/or disease-associated magnesium deficiency, seen in some metabolic conditions, has the potential to influence cardiac and vascular outcomes. Finally, we also examine the potential for magnesium supplements to be employed in the prevention and treatment of cardiovascular disorders and in the management of cardiometabolic health.
Collapse
Affiliation(s)
- Remi Fritzen
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| | - Amy Davies
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| | - Miriam Veenhuizen
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| | - Matthew Campbell
- School of Nursing and Health Sciences, University of Sunderland, Sunderland SR1 3DS, UK
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| | - Ramzi A Ajjan
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Alan J Stewart
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| |
Collapse
|
4
|
Gluvic Z, Obradovic M, Stewart AJ, Essack M, Pitt SJ, Samardzic V, Soskic S, Gojobori T, Isenovic ER. Levothyroxine Treatment and the Risk of Cardiac Arrhythmias - Focus on the Patient Submitted to Thyroid Surgery. Front Endocrinol (Lausanne) 2021; 12:758043. [PMID: 34803920 PMCID: PMC8600254 DOI: 10.3389/fendo.2021.758043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/11/2021] [Indexed: 02/05/2023] Open
Abstract
Levothyroxine (LT4) is used to treat frequently encountered endocrinopathies such as thyroid diseases. It is regularly used in clinical (overt) hypothyroidism cases and subclinical (latent) hypothyroidism cases in the last decade. Suppressive LT4 therapy is also part of the medical regimen used to manage thyroid malignancies after a thyroidectomy. LT4 treatment possesses dual effects: substituting new-onset thyroid hormone deficiency and suppressing the local and distant malignancy spreading in cancer. It is the practice to administer LT4 in less-than-high suppressive doses for growth control of thyroid nodules and goiter, even in patients with preserved thyroid function. Despite its approved safety for clinical use, LT4 can sometimes induce side-effects, more often recorded with patients under treatment with LT4 suppressive doses than in unintentionally LT4-overdosed patients. Cardiac arrhythmias and the deterioration of osteoporosis are the most frequently documented side-effects of LT4 therapy. It also lowers the threshold for the onset or aggravation of cardiac arrhythmias for patients with pre-existing heart diseases. To improve the quality of life in LT4-substituted patients, clinicians often prescribe higher doses of LT4 to reach low normal TSH levels to achieve cellular euthyroidism. In such circumstances, the risk of cardiac arrhythmias, particularly atrial fibrillation, increases, and the combined use of LT4 and triiodothyronine further complicates such risk. This review summarizes the relevant available data related to LT4 suppressive treatment and the associated risk of cardiac arrhythmia.
Collapse
Affiliation(s)
- Zoran Gluvic
- Clinic for Internal Medicine, Department of Endocrinology and Diabetes, Zemun Clinical Hospital, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Milan Obradovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Magbubah Essack
- King Abdullah University of Science and Technology (KAUST), Computer, Electrical, and Mathematical Sciences and Engineering (CEMSE) Division, Computational Bioscience Research Center (CBRC), Thuwal, Saudi Arabia
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Vladimir Samardzic
- Clinic for Internal Medicine, Department of Endocrinology and Diabetes, Zemun Clinical Hospital, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Sanja Soskic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Takashi Gojobori
- King Abdullah University of Science and Technology (KAUST), Computer, Electrical, and Mathematical Sciences and Engineering (CEMSE) Division, Computational Bioscience Research Center (CBRC), Thuwal, Saudi Arabia
| | - Esma R. Isenovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| |
Collapse
|
5
|
Martinelli A, Rice ML, Talcott JB, Diaz R, Smith S, Raza MH, Snowling MJ, Hulme C, Stein J, Hayiou-Thomas ME, Hawi Z, Kent L, Pitt SJ, Newbury DF, Paracchini S. A rare missense variant in the ATP2C2 gene is associated with language impairment and related measures. Hum Mol Genet 2021; 30:1160-1171. [PMID: 33864365 PMCID: PMC8188402 DOI: 10.1093/hmg/ddab111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 01/02/2023] Open
Abstract
At least 5% of children present unexpected difficulties in expressing and understanding spoken language. This condition is highly heritable and often co-occurs with other neurodevelopmental disorders such as dyslexia and ADHD. Through an exome sequencing analysis, we identified a rare missense variant (chr16:84405221, GRCh38.p12) in the ATP2C2 gene. ATP2C2 was implicated in language disorders by linkage and association studies, and exactly the same variant was reported previously in a different exome sequencing study for language impairment (LI). We followed up this finding by genotyping the mutation in cohorts selected for LI and comorbid disorders. We found that the variant had a higher frequency in LI cases (1.8%, N = 360) compared with cohorts selected for dyslexia (0.8%, N = 520) and ADHD (0.7%, N = 150), which presented frequencies comparable to reference databases (0.9%, N = 24 046 gnomAD controls). Additionally, we observed that carriers of the rare variant identified from a general population cohort (N = 42, ALSPAC cohort) presented, as a group, lower scores on a range of reading and language-related measures compared to controls (N = 1825; minimum P = 0.002 for non-word reading). ATP2C2 encodes for an ATPase (SPCA2) that transports calcium and manganese ions into the Golgi lumen. Our functional characterization suggested that the rare variant influences the ATPase activity of SPCA2. Thus, our results further support the role of ATP2C2 locus in language-related phenotypes and pinpoint the possible effects of a specific rare variant at molecular level.
Collapse
Affiliation(s)
| | - Mabel L Rice
- Child Language Doctoral Program, University of Kansas, Lawrence, KS, USA
| | - Joel B Talcott
- Aston Brain Centre, School of Life and Health Sciences, Aston University, Birmingham, UK
| | - Rebeca Diaz
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Shelley Smith
- Department of Neurological Sciences, University of Nebraska Medical Center, Lincoln, NE, USA
| | | | - Margaret J Snowling
- Department of Experimental Psychology and St John's College, University of Oxford, Oxford, UK
| | - Charles Hulme
- Department of Education, University of Oxford, Oxford, UK
| | - John Stein
- Department of Physiology, University of Oxford, Oxford, UK
| | | | - Ziarih Hawi
- Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Clayton, VIC, Australia
| | - Lindsey Kent
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Dianne F Newbury
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | | |
Collapse
|
6
|
Sobczak AIS, Katundu KGH, Phoenix FA, Khazaipoul S, Yu R, Lampiao F, Stefanowicz F, Blindauer CA, Pitt SJ, Smith TK, Ajjan RA, Stewart AJ. Albumin-mediated alteration of plasma zinc speciation by fatty acids modulates blood clotting in type-2 diabetes. Chem Sci 2021; 12:4079-4093. [PMID: 34163679 PMCID: PMC8179462 DOI: 10.1039/d0sc06605b] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Zn2+ is an essential regulator of coagulation and is released from activated platelets. In plasma, the free Zn2+ concentration is fine-tuned through buffering by human serum albumin (HSA). Importantly, the ability of HSA to bind/buffer Zn2+ is compromised by co-transported non-esterified fatty acids (NEFAs). Given the role of Zn2+ in blood clot formation, we hypothesise that Zn2+ displacement from HSA by NEFAs in certain conditions (such as type 2 diabetes mellitus, T2DM) impacts on the cellular and protein arms of coagulation. To test this hypothesis, we assessed the extent to which increasing concentrations of a range of medium- and long-chain NEFAs reduced Zn2+-binding ability of HSA. Amongst the NEFAs tested, palmitate (16 : 0) and stearate (18 : 0) were the most effective at suppressing zinc-binding, whilst the mono-unsaturated palmitoleate (16 : 1c9) was markedly less effective. Assessment of platelet aggregation and fibrin clotting parameters in purified systems and in pooled plasma suggested that the HSA-mediated impact of the model NEFA myristate on zinc speciation intensified the effects of Zn2+ alone. The effects of elevated Zn2+ alone on fibrin clot density and fibre thickness in a purified protein system were mirrored in samples from T2DM patients, who have derranged NEFA metabolism. Crucially, T2DM individuals had increased total plasma NEFAs compared to controls, with the concentrations of key saturated (myristate, palmitate, stearate) and mono-unsaturated (oleate, cis-vaccenate) NEFAs positively correlating with clot density. Collectively, these data strongly support the concept that elevated NEFA levels contribute to altered coagulation in T2DM through dysregulation of plasma zinc speciation. Zn2+ is an essential regulator of coagulation. In plasma, Zn2+ availability is fine-tuned by human serum albumin (HSA). Here we show that elevated fatty acid levels contribute to altered coagulation in type-2 diabetes through Zn2+ mishandling by HSA.![]()
Collapse
Affiliation(s)
- Amélie I S Sobczak
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546
| | - Kondwani G H Katundu
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546.,College of Medicine, University of Malawi Blantyre Malawi
| | - Fladia A Phoenix
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Siavash Khazaipoul
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546
| | - Ruitao Yu
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546.,Key Laboratory of Tibetan Medicine Research, Northwest Plateau Institute of Biology, Chinese Academy of Sciences 23 Xinning Road Xining Qinghai 810001 China
| | - Fanuel Lampiao
- College of Medicine, University of Malawi Blantyre Malawi
| | - Fiona Stefanowicz
- Scottish Trace Element and Micronutrient Diagnostic and Research Laboratory, Department of Biochemistry NHS Greater Glasgow and Clyde Glasgow UK
| | | | - Samantha J Pitt
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546
| | - Terry K Smith
- School of Biology, Biomedical Sciences Research Complex, University of St Andrews St Andrews UK
| | - Ramzi A Ajjan
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Leeds UK
| | - Alan J Stewart
- School of Medicine, University of St Andrews Fife KY16 9TF St Andrews UK +44 (0)1334 463482 +44 (0)1334 463546
| |
Collapse
|
7
|
Sobczak AIS, Phoenix FA, Pitt SJ, Ajjan RA, Stewart AJ. Reduced Plasma Magnesium Levels in Type-1 Diabetes Associate with Prothrombotic Changes in Fibrin Clotting and Fibrinolysis. Thromb Haemost 2020; 120:243-252. [PMID: 31942750 PMCID: PMC6997031 DOI: 10.1055/s-0039-3402808] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/11/2019] [Indexed: 12/28/2022]
Abstract
Individuals with type-1 diabetes mellitus (T1DM) have a higher risk of thrombosis and low plasma magnesium concentrations. As magnesium is a known regulator of fibrin network formation, we investigated potential associations between fibrin clot properties and plasma magnesium concentrations in 45 individuals with T1DM and 47 age- and sex-matched controls without diabetes. Fibrin clot characteristics were assessed using a validated turbidimetric assay and associations with plasma magnesium concentration were examined. Plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and lipids were measured and fibrin fiber diameters assessed using scanning electron microscopy. Fibrin clot maximum absorbance was unchanged in subjects with T1DM compared with controls, while lysis time was prolonged (p = 0.0273). No differences in fibrin fiber diameters or in lipid profile were observed between T1DM and controls. PAI-1 concentration was lower in the T1DM group compared with the controls (p = 0.0232) and positively correlated with lysis time (p = 0.0023). Plasma magnesium concentration was lower in the T1DM group compared with controls (p < 0.0001). Magnesium concentration negatively correlated with clot maximum absorbance (p = 0.0215) and lysis time (p = 0.0464). A turbidimetric fibrin clot lysis assay performed in a purified system that included PAI-1 and 0 to 3.2 mM Mg2+ showed a shortening of lysis time with increasing Mg2+ concentrations (p = 0.0004). Our findings reveal that plasma magnesium concentration is associated with changes in fibrin clot and lysis parameters.
Collapse
Affiliation(s)
| | - Fladia A. Phoenix
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| | - Ramzi A. Ajjan
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | - Alan J. Stewart
- School of Medicine, University of St Andrews, St Andrews, United Kingdom
| |
Collapse
|
8
|
Mariano G, Trunk K, Williams DJ, Monlezun L, Strahl H, Pitt SJ, Coulthurst SJ. A family of Type VI secretion system effector proteins that form ion-selective pores. Nat Commun 2019; 10:5484. [PMID: 31792213 PMCID: PMC6889166 DOI: 10.1038/s41467-019-13439-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/05/2019] [Indexed: 12/25/2022] Open
Abstract
Type VI secretion systems (T6SSs) are nanomachines widely used by bacteria to deliver toxic effector proteins directly into neighbouring cells. However, the modes of action of many effectors remain unknown. Here we report that Ssp6, an anti-bacterial effector delivered by a T6SS of the opportunistic pathogen Serratia marcescens, is a toxin that forms ion-selective pores. Ssp6 inhibits bacterial growth by causing depolarisation of the inner membrane in intoxicated cells, together with increased outer membrane permeability. Reconstruction of Ssp6 activity in vitro demonstrates that it forms cation-selective pores. A survey of bacterial genomes reveals that genes encoding Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 and similar proteins represent a new family of T6SS-delivered anti-bacterial effectors.
Collapse
Affiliation(s)
- Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Katharina Trunk
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - David J Williams
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Laura Monlezun
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Newcastle University, Richardson Road, Newcastle-upon-Tyne, NE2 4AX, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK.
| |
Collapse
|
9
|
Pitt SJ, Hawthorne JA, Garcia-Maya M, Alexandrovich A, Symonds RC, Gunn A. Identification and characterisation of anti - Pseudomonas aeruginosa proteins in mucus of the brown garden snail, Cornu aspersum. Br J Biomed Sci 2019; 76:129-136. [PMID: 30966874 DOI: 10.1080/09674845.2019.1603794] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Background: Novel antimicrobial treatments are urgently needed. Previous work has shown that the mucus of the brown garden snail (Cornu aspersum) has antimicrobial properties, in particular against type culture collection strains of Pseudomonas aeruginosa. We hypothesised that it would also be effective against clinical isolates of the bacterium and that investigation of fractions of the mucus would identify one or more proteins with anti-pseudomonal properties, which could be further characterised. Materials and methods: Mucus was extracted from snails collected from the wild. Antimicrobial activity against laboratory and clinical isolates of Ps. aeruginosa was determined in disc diffusion assays. Mucus was purified using size exclusion chromatography and fractions containing anti-pseudomonal activity identified. Mass spectroscopy and high performance liquid chromatography analysis of these fractions yielded partial peptide sequences. These were used to interrogate an RNA transcriptome generated from whole snails. Results: Mucus from C. aspersum inhibited growth of type collection strains and clinical isolates of Ps. aeruginosa. Four novel C. aspersum proteins were identified; at least three are likely to have antimicrobial properties. The most interesting is a 37.4 kDa protein whilst smaller proteins, one 17.5 kDa and one 18.6 kDa also appear to have activity against Ps. aeruginosa. Conclusions: The study has identified novel proteins with antimicrobial properties which could be used to develop treatments for use in human medicine.
Collapse
Affiliation(s)
- S J Pitt
- a School of Pharmacy and Biomolecular Sciences , University of Brighton , Brighton , UK
| | - J A Hawthorne
- a School of Pharmacy and Biomolecular Sciences , University of Brighton , Brighton , UK
| | - M Garcia-Maya
- b Randall Division of Cell and Molecular Biophysics , King's College London , London, UK
| | - A Alexandrovich
- b Randall Division of Cell and Molecular Biophysics , King's College London , London, UK
| | - R C Symonds
- c School of Natural Sciences and Psychology , Liverpool John Moores University , Liverpool , UK
| | - A Gunn
- c School of Natural Sciences and Psychology , Liverpool John Moores University , Liverpool , UK
| |
Collapse
|
10
|
Sobczak AIS, Stefanowicz F, Pitt SJ, Ajjan RA, Stewart AJ. Total plasma magnesium, zinc, copper and selenium concentrations in type-I and type-II diabetes. Biometals 2019; 32:123-138. [PMID: 30671675 PMCID: PMC7004817 DOI: 10.1007/s10534-018-00167-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 12/29/2018] [Indexed: 12/15/2022]
Abstract
Glycemia and insulin resistance are important regulators of multiple physiological processes and their dysregulation has wide-ranging consequences, including alterations in plasma concentrations of metal micronutrients. Here, magnesium, zinc, copper, selenium and glycated albumin (HbA1c) concentrations and quartile differences were examined in 45 subjects with type-I diabetes (T1DM), 54 subjects with type-II diabetes (T2DM) and 62 control subjects in order to assess potential differences between sexes and between T1DM and T2DM. Plasma magnesium concentration was decreased in T1DM subjects, with the second, third and fourth quartiles of magnesium concentrations associated with the absence of T1DM. This effect was observed in females but not males. In T2DM, the highest quartile of selenium concentrations and the third quartile of copper concentrations associated with the absence of diabetes in males. The highest quartile of magnesium concentrations was associated with the absence of T2DM in males but not females. HbA1c correlated with plasma concentrations of magnesium (negatively, in both sexes together in T1DM and T1DM males), copper (positively, in T1DM males and in both sexes together in T2DM), selenium (positively, in both sexes together in T1DM and T2DM, and T2DM females) and with zinc/copper ratio (negatively, in both sexes together in T1DM and T2DM). This study shows that plasma magnesium concentration is altered to the highest degree in T1DM, while in T2DM, plasma selenium and copper concentrations are significantly affected. This work increases our understanding of how T1DM and T2DM affects plasma metal concentrations and may have future implications for diabetes management.
Collapse
Affiliation(s)
- Amélie I S Sobczak
- School of Medicine, University of St Andrews, Medical and Biological Sciences Building, St Andrews, Fife, KY16 9TF, UK
| | - Fiona Stefanowicz
- Scottish Trace Element and Micronutrient Diagnostic and Research Laboratory, Department of Clinical Biochemistry, NHS Greater Glasgow and Clyde, Glasgow, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, Medical and Biological Sciences Building, St Andrews, Fife, KY16 9TF, UK
| | - Ramzi A Ajjan
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Alan J Stewart
- School of Medicine, University of St Andrews, Medical and Biological Sciences Building, St Andrews, Fife, KY16 9TF, UK.
| |
Collapse
|
11
|
Sobczak AIS, Pitt SJ, Stewart AJ. Influence of zinc on glycosaminoglycan neutralisation during coagulation. Metallomics 2018; 10:1180-1190. [PMID: 30132486 PMCID: PMC6148461 DOI: 10.1039/c8mt00159f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 07/24/2018] [Indexed: 12/31/2022]
Abstract
Heparan sulfate (HS), dermatan sulfate (DS) and heparin are glycosaminoglycans (GAGs) that serve as key natural and pharmacological anticoagulants. During normal clotting such agents require to be inactivated or neutralised. Several proteins have been reported to facilitate their neutralisation, which reside in platelet α-granules and are released following platelet activation. These include histidine-rich-glycoprotein (HRG), fibrinogen and high-molecular-weight kininogen (HMWK). Zinc ions (Zn2+) are also present in α-granules at a high concentration and participate in the propagation of coagulation by influencing the binding of neutralising proteins to GAGs. Zn2+ in many cases increases the affinity of these proteins to GAGs, and is thus an important regulator of GAG neutralisation and haemostasis. Binding of Zn2+ to HRG, HMWK and fibrinogen is mediated predominantly through coordination to histidine residues but the mechanisms by which Zn2+ increases the affinity of the proteins for GAGs are not yet completely clear. Here we will review current knowledge of how Zn2+ binds to and influences the neutralisation of GAGs and describe the importance of this process in both normal and pathogenic clotting.
Collapse
Affiliation(s)
- Amélie I. S. Sobczak
- School of Medicine
, University of St Andrews
,
Medical and Biological Sciences Building
, St Andrews
, Fife
, UK
.
; Fax: +44 (0)1334 463482
; Tel: +44 (0)1334 463546
| | - Samantha J. Pitt
- School of Medicine
, University of St Andrews
,
Medical and Biological Sciences Building
, St Andrews
, Fife
, UK
.
; Fax: +44 (0)1334 463482
; Tel: +44 (0)1334 463546
| | - Alan J. Stewart
- School of Medicine
, University of St Andrews
,
Medical and Biological Sciences Building
, St Andrews
, Fife
, UK
.
; Fax: +44 (0)1334 463482
; Tel: +44 (0)1334 463546
| |
Collapse
|
12
|
Abstract
The glycosaminoglycans (GAGs) heparan sulfate, dermatan sulfate, and heparin are important anticoagulants that inhibit clot formation through interactions with antithrombin and heparin cofactor II. Unfractionated heparin, low-molecular-weight heparin, and heparin-derived drugs are often the main treatments used clinically to handle coagulatory disorders. A wide range of proteins have been reported to bind and neutralize these GAGs to promote clot formation. Such neutralizing proteins are involved in a variety of other physiological processes, including inflammation, transport, and signaling. It is clear that these interactions are important for the control of normal coagulation and influence the efficacy of heparin and heparin-based therapeutics. In addition to neutralization, the anticoagulant activities of GAGs may also be regulated through reduced synthesis or by degradation. In this review, we describe GAG neutralization, the proteins involved, and the molecular processes that contribute to the regulation of anticoagulant GAG activity.
Collapse
Affiliation(s)
- Amélie I S Sobczak
- From the School of Medicine, University of St Andrews, Fife, United Kingdom
| | - Samantha J Pitt
- From the School of Medicine, University of St Andrews, Fife, United Kingdom
| | - Alan J Stewart
- From the School of Medicine, University of St Andrews, Fife, United Kingdom.
| |
Collapse
|
13
|
Jovanovic A, Sudar-Milovanovic E, Obradovic M, Pitt SJ, Stewart AJ, Zafirovic S, Stanimirovic J, Radak D, Isenovic ER. Influence of a High-Fat Diet on Cardiac iNOS in Female Rats. Curr Vasc Pharmacol 2018; 15:491-500. [PMID: 27781956 DOI: 10.2174/1570161114666161025101303] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Revised: 09/30/2016] [Accepted: 10/01/2016] [Indexed: 11/22/2022]
Abstract
BACKGROUND Overexpression of inducible nitric oxide synthase (iNOS) is a key link between high-fat (HF) diet induced obesity and cardiovascular disease. Oestradiol has cardioprotective effects that may be mediated through reduction of iNOS activity/expression. METHODS In the present study, female Wistar rats were fed a standard diet or a HF diet (42% fat) for 10 weeks. iNOS gene and protein expressions were measured in heart tissue. HF-fed rats exhibited a significant increase in cardiac iNOS mRNA by 695% (p<.05), iNOS protein level by 248% (p<0.01), without changes in nitrate/nitrite levels. Expression of CD36 protein in plasma membranes was increased by 37% (p<0.05), while the concentration of free fatty acids (FFA) was reduced by 25% (p<0.01) in HF-fed rats. Expression of the p50 subunit of nuclear factor-kB (NFkB-p50) in heart was increased by 77% (p<0.01) in HF-fed rats. Expression of protein kinase B (Akt) and extracellular signalregulated kinases 1/2 (ERK1/2) were unchanged between the groups. There was a significant increase in the ratio of phospho-Akt/total Akt but not for phospho-ERK1/2/total ERK1/2 in HF-fed rats. Estrogen receptor-α levels (by 50%; p<0.05) and serum oestradiol concentrations (by 35%; p<0.05) were shown to be significantly reduced in HF-fed rats. RESULTS AND CONCLUSION Our results revealed that a HF diet led to increased iNOS expression, most likely via a mechanism involving Akt and NFκB-p50 proteins. Decreased levels of oestradiol and ERα protein in the HF-fed group, in combination with increased iNOS levels are consistent with the hypothesis that oestradiol has a cardioprotective effect through its ability to regulate iNOS expression.
Collapse
Affiliation(s)
- Aleksandra Jovanovic
- Laboratory of Radiobiology and Molecular Genetics, Institute of Nuclear Sciences Vinca, University of Belgrade, Mike Petrovica Alasa 12-14, 11000 Belgrade. Serbia
| | - Emina Sudar-Milovanovic
- Laboratory of Radiobiology and Molecular Genetics, Institute of Nuclear Sciences Vinca, University of Belgrade, Mike Petrovica Alasa 12-14, 11000 Belgrade. Serbia
| | - Milan Obradovic
- Laboratory of Radiobiology and Molecular Genetics, Institute of Nuclear Sciences Vinca, University of Belgrade, Mike Petrovica Alasa 12-14, 11000 Belgrade. Serbia
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF. United Kingdom
| | - Alan J Stewart
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF. United Kingdom
| | - Sonja Zafirovic
- Laboratory of Radiobiology and Molecular Genetics, Institute of Nuclear Sciences Vinca, University of Belgrade, Mike Petrovica Alasa 12-14, 11000 Belgrade. Serbia
| | - Julijana Stanimirovic
- Laboratory of Radiobiology and Molecular Genetics, Institute of Nuclear Sciences Vinca, University of Belgrade, Mike Petrovica Alasa 12-14, 11000 Belgrade. Serbia
| | - Djordje Radak
- Department of Vascular Surgery, Dedinje Cardiovascular Institute, Belgrade University School of Medicine, 11040 Belgrade. Serbia
| | - Esma R Isenovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, P.O. Box 522, 11000 Belgrade. Serbia
| |
Collapse
|
14
|
Sobczak AIS, Kassaar O, Khazaipoul S, Yu R, Ajjan R, Blindauer CA, Pitt SJ, Stewart AJ. P185Regulation of coagulation by zinc: characterisation of zinc-dependent heparin neutralisation by fibrinogen and histidine-rich-glycoprotein. Cardiovasc Res 2018. [DOI: 10.1093/cvr/cvy060.142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- AIS Sobczak
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - O Kassaar
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - S Khazaipoul
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - R Yu
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - R Ajjan
- University of Leeds, Leeds Institute for Cardiovascular and Metabolic Medicine, Leeds, United Kingdom
| | - C A Blindauer
- University of Warwick, Department of Chemistry, Coventry, United Kingdom
| | - S J Pitt
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - A J Stewart
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| |
Collapse
|
15
|
Khazaipoul S, Katundu K, Blindauer CA, Pitt SJ, Stewart AJ. P571Role of free fatty acids in controlling plasma zinc dynamics and its effect on the aggregation properties of platelets. Cardiovasc Res 2018. [DOI: 10.1093/cvr/cvy060.423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- S Khazaipoul
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - K Katundu
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - C A Blindauer
- University of Warwick, Department of Chemistry, Coventry, United Kingdom
| | - S J Pitt
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| | - A J Stewart
- University of St Andrews, School of Medicine, St Andrews, United Kingdom
| |
Collapse
|
16
|
Tamburrino G, Llabrés S, Vickery ON, Pitt SJ, Zachariae U. Modulation of the Neisseria gonorrhoeae drug efflux conduit MtrE. Sci Rep 2017; 7:17091. [PMID: 29213101 PMCID: PMC5719041 DOI: 10.1038/s41598-017-16995-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 11/21/2017] [Indexed: 11/09/2022] Open
Abstract
Widespread antibiotic resistance, especially of Gram-negative bacteria, has become a severe concern for human health. Tripartite efflux pumps are one of the major contributors to resistance in Gram-negative pathogens, by efficiently expelling a broad spectrum of antibiotics from the organism. In Neisseria gonorrhoeae, one of the first bacteria for which pan-resistance has been reported, the most expressed efflux complex is MtrCDE. Here we present the electrophysiological characterisation of the outer membrane component MtrE and the membrane fusion protein MtrC, obtained by a combination of planar lipid bilayer recordings and in silico techniques. Our in vitro results show that MtrE can be regulated by periplasmic binding events and that the interaction between MtrE and MtrC is sufficient to stabilize this complex in an open state. In contrast to other efflux conduits, the open complex only displays a slight preference for cations. The maximum conductance we obtain in the in vitro recordings is comparable to that seen in our computational electrophysiology simulations conducted on the MtrE crystal structure, indicating that this state may reflect a physiologically relevant open conformation of MtrE. Our results suggest that the MtrC/E binding interface is an important modulator of MtrE function, which could potentially be targeted by new efflux inhibitors.
Collapse
Affiliation(s)
- Giulia Tamburrino
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
- Physics, School of Science and Engineering, University of Dundee, Dundee, DD1 4NH, UK
| | - Salomé Llabrés
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
- Physics, School of Science and Engineering, University of Dundee, Dundee, DD1 4NH, UK
| | - Owen N Vickery
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
- Physics, School of Science and Engineering, University of Dundee, Dundee, DD1 4NH, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF, UK.
| | - Ulrich Zachariae
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
- Physics, School of Science and Engineering, University of Dundee, Dundee, DD1 4NH, UK.
| |
Collapse
|
17
|
Reilly-O'Donnell B, Robertson GB, Karumbi A, McIntyre C, Bal W, Nishi M, Takeshima H, Stewart AJ, Pitt SJ. Dysregulated Zn 2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca 2+ leakage. J Biol Chem 2017. [PMID: 28630041 PMCID: PMC5555195 DOI: 10.1074/jbc.m117.781708] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Aberrant Zn2+ homeostasis is associated with dysregulated intracellular Ca2+ release, resulting in chronic heart failure. In the failing heart a small population of cardiac ryanodine receptors (RyR2) displays sub-conductance-state gating leading to Ca2+ leakage from sarcoplasmic reticulum (SR) stores, which impairs cardiac contractility. Previous evidence suggests contribution of RyR2-independent Ca2+ leakage through an uncharacterized mechanism. We sought to examine the role of Zn2+ in shaping intracellular Ca2+ release in cardiac muscle. Cardiac SR vesicles prepared from sheep or mouse ventricular tissue were incorporated into phospholipid bilayers under voltage-clamp conditions, and the direct action of Zn2+ on RyR2 channel function was examined. Under diastolic conditions, the addition of pathophysiological concentrations of Zn2+ (≥2 nm) caused dysregulated RyR2-channel openings. Our data also revealed that RyR2 channels are not the only SR Ca2+-permeable channels regulated by Zn2+. Elevating the cytosolic Zn2+ concentration to 1 nm increased the activity of the transmembrane protein mitsugumin 23 (MG23). The current amplitude of the MG23 full-open state was consistent with that previously reported for RyR2 sub-conductance gating, suggesting that in heart failure in which Zn2+ levels are elevated, RyR2 channels do not gate in a sub-conductance state, but rather MG23-gating becomes more apparent. We also show that in H9C2 cells exposed to ischemic conditions, intracellular Zn2+ levels are elevated, coinciding with increased MG23 expression. In conclusion, these data suggest that dysregulated Zn2+ homeostasis alters the function of both RyR2 and MG23 and that both ion channels play a key role in diastolic SR Ca2+ leakage.
Collapse
Affiliation(s)
- Benedict Reilly-O'Donnell
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom
| | - Gavin B Robertson
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom
| | - Angela Karumbi
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom
| | - Connor McIntyre
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom
| | - Wojciech Bal
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Science, Warsaw, 02-106 Poland, and
| | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Alan J Stewart
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom
| | - Samantha J Pitt
- From the School of Medicine, University of St. Andrews, St. Andrews, KY16 9TF, Scotland, United Kingdom,
| |
Collapse
|
18
|
Zafirovic S, Obradovic M, Sudar-Milovanovic E, Jovanovic A, Stanimirovic J, Stewart AJ, Pitt SJ, Isenovic ER. 17β-Estradiol protects against the effects of a high fat diet on cardiac glucose, lipid and nitric oxide metabolism in rats. Mol Cell Endocrinol 2017; 446:12-20. [PMID: 28163099 DOI: 10.1016/j.mce.2017.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/17/2017] [Accepted: 02/01/2017] [Indexed: 12/26/2022]
Abstract
The aim of this study was to investigate the in vivo effects of 17β-estradiol (E2) on myocardial metabolism and inducible nitric oxide synthase (iNOS) expression/activity in obese rats. Male Wistar rats were fed with a normal or a high fat (HF) diet (42% fat) for 10 weeks. Half of the HF fed rats were treated with a single dose of E2 while the other half were placebo-treated. 24 h after treatment animals were sacrificed. E2 reduced cardiac free fatty acid (FFA) (p < 0.05), L-arginine (p < 0.01), iNOS mRNA (p < 0.01), and protein (p < 0.05) levels and translocation of the FFA transporter (CD36) (p < 0.01) to the plasma membrane (PM) in HF fed rats. In contrast, Akt phosphorylation at Thr308 (p < 0.05) and translocation of the glucose transporter GLUT4 (p < 0.05) to the PM increased after E2 treatment in HF rats. Our results indicate that E2 acts via the PI3K/Akt signalling pathway to partially protect myocardial metabolism by attenuating the detrimental effects of increased iNOS expression/activity in HF fed rats.
Collapse
Affiliation(s)
- Sonja Zafirovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Milan Obradovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Emina Sudar-Milovanovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Aleksandra Jovanovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Julijana Stanimirovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Alan J Stewart
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, United Kingdom.
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, United Kingdom.
| | - Esma R Isenovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| |
Collapse
|
19
|
Woodier J, Rainbow RD, Stewart AJ, Pitt SJ. Response to Qian and Colvin: Zinc-mediated Regulation of the Cardiac Ryanodine Receptor Occurs via Multiple Binding Sites. J Biol Chem 2016; 291:4267. [PMID: 26896486 DOI: 10.1074/jbc.l115.713214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Jason Woodier
- School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| | - Richard D Rainbow
- Department of Cardiovascular Sciences, University of Leicester, Clinical Sciences Wing, Glenfield General Hospital, Leicester LE3 9QP, United Kingdom
| | - Alan J Stewart
- School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| | - Samantha J Pitt
- School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| |
Collapse
|
20
|
Pitt SJ, Graham MA, Dedi CG, Taylor-Harris PM, Gunn A. Antimicrobial properties of mucus from the brown garden snail Helix aspersa. Br J Biomed Sci 2016; 72:174-81; quiz 208. [PMID: 26738399 DOI: 10.1080/09674845.2015.11665749] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Research into naturally occurring antimicrobial substances has yielded effective treatments. One area of interest is peptides and proteins produced by invertebrates as part of their defence system, including the contents of mollusc mucus. Mucus produced by the African giant land snail, Achatina fulica has been reported to contain two proteins with broad-spectrum antibacterial activity. Mucus from the brown garden snail, Helix aspersa, appears to have skin regeneration properties. This study sought to investigate the antimicrobial properties of H. aspersa mucus. Mucus was collected from H. aspersa snails, diluted in phosphate-buffered saline (PBS), with the supernatant tested against a wide range of organisms in a disc-diffusion antimicrobial assay. This was followed with comparative experiments involving A. fulica, including bacteriophage assays. Mucus from both species of snail was passed through a series of protein size separation columns in order to determine the approximate size of the antimicrobial substance. Electrophoresis was also carried out on the H. aspersa mucus. Results indicated that H. aspersa mucus had a strong antibacterial effect against several strains of Pseudomonas aeruginosa and a weak effect against Staphylococcus aureus. Mucus from A. fulica also inhibited the growth of S. aureus, but the broad spectrum of activity reported by other workers was not observed. Antimicrobial activity was not caused by bacteriophage. Size separation experiments indicated that the antimicrobial substance(s) in H. aspersa were between 30 and 100 kDa. Electrophoresis revealed two proteins in this region (30-40 kDa and 50-60 kDa). These do not correspond with antimicrobial proteins previously reported in A. fulica. This study found one or more novel antimicrobial agents in H. aspersa mucus, with a strong effect against P. aeruginosa.
Collapse
|
21
|
Pitt SJ, Reilly-O'Donnell B, Sitsapesan R. Exploring the biophysical evidence that mammalian two-pore channels are NAADP-activated calcium-permeable channels. J Physiol 2016; 594:4171-9. [PMID: 26872338 DOI: 10.1113/jp270936] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/15/2016] [Indexed: 01/15/2023] Open
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) potently releases Ca(2+) from acidic intracellular endolysosomal Ca(2+) stores. It is widely accepted that two types of two-pore channels, termed TPC1 and TPC2, are responsible for the NAADP-mediated Ca(2+) release but the underlying mechanisms regulating their gating appear to be different. For example, although both TPC1 and TPC2 are activated by NAADP, TPC1 appears to be additionally regulated by cytosolic Ca(2+) . Ion conduction and permeability also differ markedly. TPC1 and TPC2 are permeable to a range of cations although biophysical experiments suggest that TPC2 is slightly more selective for Ca(2+) over K(+) than TPC1 and hence capable of releasing greater quantities of Ca(2+) from acidic stores. TPC1 is also permeable to H(+) and therefore may play a role in regulating lysosomal and cytosolic pH, possibly creating localised acidic domains. The significantly different gating and ion conducting properties of TPC1 and TPC2 suggest that these two ion channels may play complementary physiological roles as Ca(2+) -release channels of the endolysosomal system.
Collapse
Affiliation(s)
- Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF, UK
| | | | | |
Collapse
|
22
|
Robertson GB, Reilly-O'Donnell B, Balmforth C, Pitt SJ. Zinc Modulates Skeletal Ryanodine Receptor Function Resulting in Altered Sarcoplasmic Reticulum Calcium Release. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
23
|
Reilly-O'Donnell B, Robertson GB, Karumbi A, Stewart AJ, Pitt SJ. Diastolic Calcium Leak and the Role of Zinc. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
24
|
Affiliation(s)
- Alan J Stewart
- a School of Medicine, University of St Andrews ; St Andrews , UK
| | - Samantha J Pitt
- a School of Medicine, University of St Andrews ; St Andrews , UK
| |
Collapse
|
25
|
Abstract
Aberrant Zn2+ homeostasis is a hallmark of certain cardiomyopathies associated with altered contractile force. In this study, we addressed whether Zn2+ modulates cardiac ryanodine receptor gating and Ca2+ dynamics in isolated cardiomyocytes. We reveal that Zn2+ is a high affinity regulator of RyR2 displaying three modes of operation. Picomolar free Zn2+ concentrations potentiate RyR2 responses, but channel activation is still dependent on the presence of cytosolic Ca2+. At concentrations of free Zn2+ >1 nm, Zn2+ is the main activating ligand, and the dependence on Ca2+ is removed. Zn2+ is therefore a higher affinity activator of RyR2 than Ca2+. Millimolar levels of free Zn2+ were found to inhibit channel openings. In cardiomyocytes, consistent with our single channel results, we show that Zn2+ modulates both the frequency and amplitude of Ca2+ waves in a concentration-dependent manner and that physiological levels of Zn2+ elicit Ca2+ release in the absence of activating levels of cytosolic Ca2+. This highlights a new role for intracellular Zn2+ in shaping Ca2+ dynamics in cardiomyocytes through modulation of RyR2 gating.
Collapse
Affiliation(s)
- Jason Woodier
- From the School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| | - Richard D Rainbow
- the Department of Cardiovascular Sciences, University of Leicester, Clinical Sciences Wing, Glenfield General Hospital, Leicester LE3 9QP, United Kingdom
| | - Alan J Stewart
- From the School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| | - Samantha J Pitt
- From the School of Medicine, University of St. Andrews, St. Andrews KY16 9TF, United Kingdom and
| |
Collapse
|
26
|
Venturi E, Galfré E, O'Brien F, Pitt SJ, Bellamy S, Sessions RB, Sitsapesan R. FKBP12.6 activates RyR1: investigating the amino acid residues critical for channel modulation. Biophys J 2014; 106:824-33. [PMID: 24559985 PMCID: PMC3945099 DOI: 10.1016/j.bpj.2013.12.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 11/25/2013] [Accepted: 12/19/2013] [Indexed: 02/02/2023] Open
Abstract
We have previously shown that FKBP12 associates with RyR2 in cardiac muscle and that it modulates RyR2 function differently to FKBP12.6. We now investigate how these proteins affect the single-channel behavior of RyR1 derived from rabbit skeletal muscle. Our results show that FKBP12.6 activates and FKBP12 inhibits RyR1. It is likely that both proteins compete for the same binding sites on RyR1 because channels that are preactivated by FKBP12.6 cannot be subsequently inhibited by FKBP12. We produced a mutant FKBP12 molecule (FKBP12E31Q/D32N/W59F) where the residues Glu(31), Asp(32), and Trp(59) were converted to the corresponding residues in FKBP12.6. With respect to the functional regulation of RyR1 and RyR2, the FKBP12E31Q/D32N/W59F mutant lost all ability to behave like FKBP12 and instead behaved like FKBP12.6. FKBP12E31Q/D32N/W59F activated RyR1 but was not capable of activating RyR2. In conclusion, FKBP12.6 activates RyR1, whereas FKBP12 activates RyR2 and this selective activator phenotype is determined within the amino acid residues Glu(31), Asp(32), and Trp(59) in FKBP12 and Gln(31), Asn(32), and Phe(59) in FKBP12.6. The opposing but different effects of FKBP12 and FKBP12.6 on RyR1 and RyR2 channel gating provide scope for diversity of regulation in different tissues.
Collapse
Affiliation(s)
- Elisa Venturi
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Elena Galfré
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Fiona O'Brien
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Samantha J Pitt
- School of Medicine, University of St. Andrews, St. Andrew, United Kingdom
| | - Stuart Bellamy
- Centre for Nanoscience and Quantum Information (NSQI), University of Bristol, Bristol, United Kingdom
| | | | - Rebecca Sitsapesan
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
| |
Collapse
|
27
|
Pitt SJ, Lam AKM, Rietdorf K, Galione A, Sitsapesan R. Reconstituted human TPC1 is a proton-permeable ion channel and is activated by NAADP or Ca2+. Sci Signal 2014; 7:ra46. [PMID: 24847115 DOI: 10.1126/scisignal.2004854] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
NAADP potently triggers Ca2+ release from acidic lysosomal and endolysosomal Ca2+ stores. Human two-pore channels (TPC1 and TPC2), which are located on these stores, are involved in this process, but there is controversy over whether TPC1 and TPC2 constitute the Ca2+ release channels. We therefore examined the single-channel properties of human TPC1 after reconstitution into bilayers of controlled composition. We found that TPC1 was permeable not only to Ca2+ but also to monovalent cations and that permeability to protons was the highest (relative permeability sequence: H+ >> K+ > Na(+) ≥ Ca2+). NAADP or Ca2+ activated TPC1, and the presence of one of these ligands was required for channel activation. The endolysosome-located lipid phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] had no effect on TPC1 open probability but significantly increased the relative permeability of Na+ to Ca2+ and of H+ to Ca2+. Furthermore, our data showed that, although both TPC1 and TPC2 are stimulated by NAADP, these channels differ in ion selectivity and modulation by Ca2+ and pH. We propose that NAADP triggers H+ release from lysosomes and endolysomes through activation of TPC1, but that the Ca2+ -releasing ability of TPC1 will depend on the ionic composition of the acidic stores and may be influenced by other regulators that affect TPC1 ion permeation.
Collapse
Affiliation(s)
- Samantha J Pitt
- School of Medicine, University of St Andrews, St Andrews KY16 9TF, UK
| | - Andy K M Lam
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Katja Rietdorf
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Rebecca Sitsapesan
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| |
Collapse
|
28
|
Obradovic M, Stewart AJ, Pitt SJ, Labudovic-Borovic M, Sudar E, Petrovic V, Zafirovic S, Maravic-Stojkovic V, Vasic V, Isenovic ER. In vivo effects of 17β-estradiol on cardiac Na(+)/K(+)-ATPase expression and activity in rat heart. Mol Cell Endocrinol 2014; 388:58-68. [PMID: 24662727 DOI: 10.1016/j.mce.2014.03.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 03/15/2014] [Accepted: 03/15/2014] [Indexed: 12/24/2022]
Abstract
In this study the in vivo effects of estradiol in regulating Na(+)/K(+)-ATPase function in rat heart was studied. Adult male Wistar rats were treated with estradiol (40μg/kg, i.p.) and after 24h the animals were sacrificed and the heart excised. Following estradiol administration, cardiac Na(+)/K(+)-ATPase activity, expression of the α1 subunit, and phosphorylation of the α1 subunit were significantly increased. These animals also had significantly decreased levels of digoxin-like immunoreactive factor(s). Na(+) levels were also significantly reduced but to a level that was still within the normal physiological range, highlighting the ability of the Na(+)/K(+)-ATPase to balance the ionic composition following treatment with estradiol. Estradiol treated rats also showed increased phosphorylation of protein kinase B (Akt), and extracellular-signal-regulated kinase 1/2 (ERK1/2). We therefore suggest a role for Akt and/or ERK1/2 in estradiol-mediated regulation of cardiac Na(+)/K(+)-ATPase expression and activity in rat heart.
Collapse
Affiliation(s)
- Milan Obradovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Alan J Stewart
- School of Medicine, University of St Andrews, North Haugh, St Andrews KY16 9TF, United Kingdom.
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews KY16 9TF, United Kingdom.
| | - Milica Labudovic-Borovic
- Institute of Histology and Embryology "Aleksandar Đ. Kostić", Faculty of Medicine, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia.
| | - Emina Sudar
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Voin Petrovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Physical Chemistry, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Sonja Zafirovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Vera Maravic-Stojkovic
- Dedinje Cardiovascular Institute, Belgrade University, School of Medicine, Heroja Milana Tepica 1, 11000 Belgrade, Serbia.
| | - Vesna Vasic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Physical Chemistry, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| | - Esma R Isenovic
- Institute of Nuclear Sciences Vinca, University of Belgrade, Laboratory of Radiobiology and Molecular Genetics, Mike Petrovica Alasa 12-14, 11000 Belgrade, Serbia.
| |
Collapse
|
29
|
Venturi E, Matyjaszkiewicz A, Pitt SJ, Tsaneva-Atanasova K, Nishi M, Yamazaki D, Takeshima H, Sitsapesan R. TRIC-B channels display labile gating: evidence from the TRIC-A knockout mouse model. Pflugers Arch 2013; 465:1135-48. [PMID: 23467973 PMCID: PMC3732801 DOI: 10.1007/s00424-013-1251-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/24/2013] [Accepted: 02/11/2013] [Indexed: 11/25/2022]
Abstract
Sarcoplasmic/endoplasmic reticulum (SR) and nuclear membranes contain two related cation channels named TRIC-A and TRIC-B. In many tissues, both subtypes are co-expressed, making it impossible to distinguish the distinct single-channel properties of each subtype. We therefore incorporated skeletal muscle SR vesicles derived from Tric-a-knockout mice into bilayers in order to characterise the biophysical properties of native TRIC-B without possible misclassification of the channels as TRIC-A, and without potential distortion of functional properties by detergent purification protocols. The native TRIC-B channels were ideally selective for cations. In symmetrical 210 mM K+, the maximum (full) open channel level (199 pS) was equivalent to that observed when wild-type SR vesicles were incorporated into bilayers. Analysis of TRIC-B gating revealed complex and variable behaviour. Four main sub-conductance levels were observed at approximately 80 % (161 pS), 60 % (123 pS), 46 % (93 pS), and 30 % (60 pS) of the full open state. Seventy-five percent of the channels were voltage sensitive with Po being markedly reduced at negative holding potentials. The frequent, rapid transitions between TRIC-B sub-conductance states prevented development of reliable gating models using conventional single-channel analysis. Instead, we used mean-variance plots to highlight key features of TRIC-B gating in a more accurate and visually useful manner. Our study provides the first biophysical characterisation of native TRIC-B channels and indicates that this channel would be suited to provide counter current in response to Ca2+ release from the SR. Further experiments are required to distinguish the distinct functional properties of TRIC-A and TRIC-B and understand their individual but complementary physiological roles.
Collapse
Affiliation(s)
- Elisa Venturi
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
| | - Antoni Matyjaszkiewicz
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
- Department of Engineering Mathematics, University of Bristol, Bristol, BS8 1TR UK
- Bristol Centre for Complexity Sciences, University of Bristol, Bristol, BS8 1TR UK
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF UK
| | | | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Daiju Yamazaki
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Rebecca Sitsapesan
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
| |
Collapse
|
30
|
Galfré E, Pitt SJ, Venturi E, Sitsapesan M, Zaccai NR, Tsaneva-Atanasova K, O'Neill S, Sitsapesan R. FKBP12 activates the cardiac ryanodine receptor Ca2+-release channel and is antagonised by FKBP12.6. PLoS One 2012; 7:e31956. [PMID: 22363773 PMCID: PMC3283708 DOI: 10.1371/journal.pone.0031956] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 01/16/2012] [Indexed: 11/18/2022] Open
Abstract
Changes in FKBP12.6 binding to cardiac ryanodine receptors (RyR2) are implicated in mediating disturbances in Ca(2+)-homeostasis in heart failure but there is controversy over the functional effects of FKBP12.6 on RyR2 channel gating. We have therefore investigated the effects of FKBP12.6 and another structurally similar molecule, FKBP12, which is far more abundant in heart, on the gating of single sheep RyR2 channels incorporated into planar phospholipid bilayers and on spontaneous waves of Ca(2+)-induced Ca(2+)-release in rat isolated permeabilised cardiac cells. We demonstrate that FKBP12 is a high affinity activator of RyR2, sensitising the channel to cytosolic Ca(2+), whereas FKBP12.6 has very low efficacy, but can antagonise the effects of FKBP12. Mathematical modelling of the data shows the importance of the relative concentrations of FKBP12 and FKBP12.6 in determining RyR2 activity. Consistent with the single-channel results, physiological concentrations of FKBP12 (3 µM) increased Ca(2+)-wave frequency and decreased the SR Ca(2+)-content in cardiac cells. FKBP12.6, itself, had no effect on wave frequency but antagonised the effects of FKBP12.We provide a biophysical analysis of the mechanisms by which FK-binding proteins can regulate RyR2 single-channel gating. Our data indicate that FKBP12, in addition to FKBP12.6, may be important in regulating RyR2 function in the heart. In heart failure, it is possible that an alteration in the dual regulation of RyR2 by FKBP12 and FKBP12.6 may occur. This could contribute towards a higher RyR2 open probability, 'leaky' RyR2 channels and Ca(2+)-dependent arrhythmias.
Collapse
Affiliation(s)
- Elena Galfré
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | - Samantha J. Pitt
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | - Elisa Venturi
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | - Mano Sitsapesan
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | - Nathan R. Zaccai
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | | | - Stephen O'Neill
- Cardiovascular Research Group, Core Technology Facility, University of Manchester, Manchester, United Kingdom
| | - Rebecca Sitsapesan
- School of Physiology & Pharmacology, Centre for Nanoscience and Quantum Information, and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| |
Collapse
|
31
|
Pitt SJ, Cunningham JM. Biomedical scientist training officers' evaluation of integrated (co-terminus) Applied Biomedical Science BSc programmes: a multicentre study. Br J Biomed Sci 2011; 68:79-85. [PMID: 21706919 DOI: 10.1080/09674845.2011.11730328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The introduction of the Institute of Biomedical Science (IBMS) portfolio for pre-registration training in 2003 allowed universities to develop integrated (co-terminus) biomedical science BSc programmes. Students undertake structured placements within clinical pathology laboratories as part of their degree. The clinical training and professional development of students is undertaken by training officers (TOs), who are experienced Health Professions Council (HPC)-registered biomedical scientists and usually also members of the IBMS. This study aims to evaluate TOs' perceptions of these integrated degrees as a means of delivering pre-registration training for biomedical scientists. A questionnaire to collect quantitative data and be completed anonymously was sent to TOs, via staff at participating universities. Items considered TOs' perceptions in four categories: how well students fitted into the laboratory team, their professional and scientific development, the impact of delivering integrated degrees on service delivery, and the commitment to training students. Surveys took place in 2007, 2008 and 2009 and involved TOs taking students from 10, 14 and 17 universities each year, respectively. The response rates to the survey were 60% in 2007, 34% in 2008 and 12% in 2009. Participants were representative in terms of age, gender and pathology discipline and had a broad range of experience with students. The overall mean score for TOs perceptions was 3.38 in 2007 which increased significantly to 3.99 in 2009 (Kruskall Wallis test chi2 = 21.13, P<0.01). Mean scores in three of the four categories were positive in 2007, although the impact on service delivery was perceived negatively. In all areas, means were significantly greater in 2009. The results indicate that TOs view the integrated degrees favourably and are happy with the scientific and professional development of students. Although designing training sessions suitable for undergraduates took extra work initially, TOs are committed to delivering the training.
Collapse
Affiliation(s)
- S J Pitt
- School of Pharmacy and Biomolecular Sciences, Brighton University, Huxley Building, Lewes Road, Brighton BN2 4GJ, UK.
| | | |
Collapse
|
32
|
Venturi E, Mio K, Nishi M, Ogura T, Moriya T, Pitt SJ, Okuda K, Kakizawa S, Sitsapesan R, Sato C, Takeshima H. Mitsugumin 23 forms a massive bowl-shaped assembly and cation-conducting channel. Biochemistry 2011; 50:2623-32. [PMID: 21381722 PMCID: PMC3065873 DOI: 10.1021/bi1019447] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mitsugumin 23 (MG23) is a 23 kDa transmembrane protein localized to the sarcoplasmic/endoplasmic reticulum and nuclear membranes in a wide variety of cells. Although the characteristics imply the participation in a fundamental function in intracellular membrane systems, the physiological role of MG23 is unknown. Here we report the biochemical and biophysical characterization of MG23. Hydropathicity profile and limited proteolytic analysis proposed three transmembrane segments in the MG23 primary structure. Chemical cross-linking analysis suggested a homo-oligomeric assembly of MG23. Ultrastructural observations detected a large symmetrical particle as the predominant component and a small asymmetric assembly as the second major component in highly purified MG23 preparations. Single-particle three-dimensional reconstruction revealed that MG23 forms a large bowl-shaped complex equipped with a putative central pore, which is considered an assembly of the small asymmetric subunit. After reconstitution into planar phospholipid bilayers, purified MG23 behaved as a voltage-dependent, cation-conducting channel, permeable to both K(+) and Ca(2+). A feature of MG23 gating was that multiple channels always appeared to be gating together in the bilayer. Our observations suggest that the bowl-shaped MG23 can transiently assemble and disassemble. These building transitions may underlie the unusual channel gating behavior of MG23 and allow rapid cationic flux across intracellular membrane systems.
Collapse
Affiliation(s)
- Elisa Venturi
- School of Physiology and Pharmacology, Bristol Heart Institute and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Carter S, Pitt SJ, Colyer J, Sitsapesan R. Ca²+-dependent phosphorylation of RyR2 can uncouple channel gating from direct cytosolic Ca²+ regulation. J Membr Biol 2011; 240:21-33. [PMID: 21274522 PMCID: PMC3047053 DOI: 10.1007/s00232-011-9339-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 01/02/2011] [Indexed: 12/03/2022]
Abstract
Phosphorylation of the cardiac ryanodine receptor (RyR2) is thought to be important not only for normal cardiac excitation-contraction coupling but also in exacerbating abnormalities in Ca²+ homeostasis in heart failure. Linking phosphorylation to specific changes in the single-channel function of RyR2 has proved very difficult, yielding much controversy within the field. We therefore investigated the mechanistic changes that take place at the single-channel level after phosphorylating RyR2 and, in particular, the idea that PKA-dependent phosphorylation increases RyR2 sensitivity to cytosolic Ca²+. We show that hyperphosphorylation by exogenous PKA increases open probability (P(o)) but, crucially, RyR2 becomes uncoupled from the influence of cytosolic Ca²+; lowering [Ca²+] to subactivating levels no longer closes the channels. Phosphatase (PP1) treatment reverses these gating changes, returning the channels to a Ca²+-sensitive mode of gating. We additionally found that cytosolic incubation with Mg²+/ATP in the absence of exogenously added kinase could phosphorylate RyR2 in approximately 50% of channels, thereby indicating that an endogenous kinase incorporates into the bilayer together with RyR2. Channels activated by the endogenous kinase exhibited identical changes in gating behavior to those activated by exogenous PKA, including uncoupling from the influence of cytosolic Ca²+. We show that the endogenous kinase is both Ca²+-dependent and sensitive to inhibitors of PKC. Moreover, the Ca²+-dependent, endogenous kinase-induced changes in RyR2 gating do not appear to be related to phosphorylation of serine-2809. Further work is required to investigate the identity and physiological role of this Ca²+-dependent endogenous kinase that can uncouple RyR2 gating from direct cytosolic Ca²+ regulation.
Collapse
Affiliation(s)
- Simon Carter
- School of Physiology and Pharmacology and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, BS8 1TD UK
| | - Samantha J. Pitt
- School of Physiology and Pharmacology and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, BS8 1TD UK
| | - John Colyer
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Rebecca Sitsapesan
- School of Physiology and Pharmacology and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, BS8 1TD UK
| |
Collapse
|
34
|
Pitt SJ, Funnell TM, Zhu MX, Parrington J, Ruas M, Galione A, Sitsapesan R. TPC2 is a Novel NAADP-Sensitive Intracellular Ca2+-Release Channel with Unique Gating Characteristics. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.2557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
|
35
|
Venturi E, Mio K, Nishi M, Ogura T, Moriya T, Pitt SJ, Okuda K, Sitsapesan R, Sato C, Takeshima H. Mitsugumin23, a Protein Associated with Intracellular Calcium Stores, Behaves as an Ion-Channel that can Conduct Calcium. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
|
36
|
Galfrè E, Sitsapesan M, Pitt SJ, Venturi E, O'Neill S, Sitsapesan R. FKBP12.6 ‘Stabilises’ Cardiac SR Ca2+-Release by Antagonising High-Affinity Reversible Activation of RyR2 by FKBP12. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.3255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
|
37
|
Venturi E, Pitt SJ, Sitsapesan M, Galfré E, Sitsapesan R. Rapamycin is a Deceptive Tool for Probing Functional Interactions Between FK506-Binding Proteins and Ryanodine Receptors. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.2461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
38
|
Pitt SJ, Park KH, Nishi M, Urashima T, Aoki S, Yamazaki D, Ma J, Takeshima H, Sitsapesan R. Charade of the SR K+-channel: two ion-channels, TRIC-A and TRIC-B, masquerade as a single K+-channel. Biophys J 2010; 99:417-26. [PMID: 20643059 DOI: 10.1016/j.bpj.2010.04.051] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 04/08/2010] [Accepted: 04/23/2010] [Indexed: 11/27/2022] Open
Abstract
The presence of a sarcoplasmic reticulum (SR) K+-selective ion-channel has been known for >30 years yet the molecular identity of this channel has remained a mystery. Recently, an SR trimeric intracellular cation channel (TRIC-A) was identified but it did not exhibit all expected characteristics of the SR K+-channel. We show that a related SR protein, TRIC-B, also behaves as a cation-selective ion-channel. Comparison of the single-channel properties of purified TRIC-A and TRIC-B in symmetrical 210 mM K+ solutions, show that TRIC-B has a single-channel conductance of 138 pS with subconductance levels of 59 and 35 pS, whereas TRIC-A exhibits full- and subconductance open states of 192 and 129 pS respectively. We suggest that the K+-current fluctuations observed after incorporating cardiac or skeletal SR into bilayers, can be explained by the gating of both TRIC-A and TRIC-B channels suggesting that the SR K+-channel is not a single, distinct entity. Importantly, TRIC-A is regulated strongly by trans-membrane voltage whereas TRIC-B is activated primarily by micromolar cytosolic Ca2+ and inhibited by luminal Ca2+. Thus, TRIC-A and TRIC-B channels are regulated by different mechanisms, thereby providing maximum flexibility and scope for facilitating monovalent cation flux across the SR membrane.
Collapse
Affiliation(s)
- Samantha J Pitt
- Department of Physiology and Pharmacology and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Pitt SJ, Funnell TM, Sitsapesan M, Venturi E, Rietdorf K, Ruas M, Ganesan A, Gosain R, Churchill GC, Zhu MX, Parrington J, Galione A, Sitsapesan R. TPC2 is a novel NAADP-sensitive Ca2+ release channel, operating as a dual sensor of luminal pH and Ca2+. J Biol Chem 2010; 285:35039-46. [PMID: 20720007 PMCID: PMC2966118 DOI: 10.1074/jbc.m110.156927] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a molecule capable of initiating the release of intracellular Ca2+ required for many essential cellular processes. Recent evidence links two-pore channels (TPCs) with NAADP-induced release of Ca2+ from lysosome-like acidic organelles; however, there has been no direct demonstration that TPCs can act as NAADP-sensitive Ca2+ release channels. Controversial evidence also proposes ryanodine receptors as the primary target of NAADP. We show that TPC2, the major lysosomal targeted isoform, is a cation channel with selectivity for Ca2+ that will enable it to act as a Ca2+ release channel in the cellular environment. NAADP opens TPC2 channels in a concentration-dependent manner, binding to high affinity activation and low affinity inhibition sites. At the core of this process is the luminal environment of the channel. The sensitivity of TPC2 to NAADP is steeply dependent on the luminal [Ca2+] allowing extremely low levels of NAADP to open the channel. In parallel, luminal pH controls NAADP affinity for TPC2 by switching from reversible activation of TPC2 at low pH to irreversible activation at neutral pH. Further evidence earmarking TPCs as the likely pathway for NAADP-induced intracellular Ca2+ release is obtained from the use of Ned-19, the selective blocker of cellular NAADP-induced Ca2+ release. Ned-19 antagonizes NAADP-activation of TPC2 in a non-competitive manner at 1 μm but potentiates NAADP activation at nanomolar concentrations. This single-channel study provides a long awaited molecular basis for the peculiar mechanistic features of NAADP signaling and a framework for understanding how NAADP can mediate key physiological events.
Collapse
Affiliation(s)
- Samantha J Pitt
- School of Physiology and Pharmacology, Medical Sciences Building, and Center for Nanoscience and Quantum Information, University of Bristol, Bristol BS8 1TD, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Sitsapesan R, Pitt SJ, Venturi E, Galfre E, O'Neill S, Sitsapesan M. FKBP12 is a High Affinity, Reversible Activator of RyR2, and FKBP12.6 Antagonises Its Actions. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.1630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
|
41
|
Pitt SJ, Martinez-Pinna J, Barnard EA, Mahaut-Smith MP. Potentiation of P2Y Receptors by Physiological Elevations of Extracellular K+via a Mechanism Independent of Ca2+Influx. Mol Pharmacol 2005; 67:1705-13. [PMID: 15710744 DOI: 10.1124/mol.104.009902] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many physiological and pathophysiological situations generate a significant increase in extracellular K+ concentration. This is known to influence a number of membrane conductances and exchangers, whereas direct effects of K+ on the activation of G protein-coupled receptors have not been reported. We now show that Ca2+ release evoked by P2Y1 receptors expressed in 1321-N1 astrocytoma cells is markedly potentiated by small increases in external K+ concentration. This effect was blocked by the phospholipase-C inhibitor U-73122 (1-[6-[[17 beta]-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione), but not by its analog U-73343 (1-[6-[[17 beta]-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5-pyrrolidinedione), and not by nifedipine, Ni2+, Cd2+, or Gd3+. Thus, K+ enhances d-myo-inositol 1,4,5-trisphosphate-dependent Ca2+ release without a requirement for Ca2+ influx. The cation dependence of this effect displayed the order K+ > Rb+ > N-methyl-D-glucamine+, and Cs+ and choline+ were ineffective. The potentiation by K+ is half-maximal at an increase of 2.6 mM (total K+ of 7.6 mM). K+ caused a reduction in EC50 (2.7-fold for a 29 mM increase) without a change of slope; thus, the greatest effect was observed at near-threshold agonist levels. The response to K+ can be explained in part by depolarization-dependent potentiation of P2Y1 receptors [J Physiol (Lond) 555:61-70, 2004]. However, electrophysiological recordings of 1321-N1 cells and megakaryocytes demonstrated that K+ also amplifies ADP-evoked Ca2+ responses independently of changes in membrane potential. Elevated K+ also amplified endogenous UTP-dependent Ca2+ responses in human embryonic kidney 293 cells, suggesting that other P2Y receptors are K(+)-dependent. P2Y receptors display a widespread tissue distribution; therefore, their modulation by small changes in extracellular K+ may represent a novel means of autocrine and paracrine regulation of cellular activity.
Collapse
Affiliation(s)
- Samantha J Pitt
- Department of Physiology, University of Cambridge, United Kingdom
| | | | | | | |
Collapse
|
42
|
Pitt SJ, Rasanayagam P, Sutehall GM. Evaluation of the continuing professional development scheme of the Institute of Biomedical Science. Br J Biomed Sci 2004; 61:133-7. [PMID: 15462258 DOI: 10.1080/09674845.2004.11732658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
As part of a review of the Continuing Professional Development (CPD) scheme of the Institute of Biomedical Science (IBMS), 10 years after it started, a survey was conducted. A questionnaire was distributed to all Institute members in July 2002. By the end of September, replies had been received from 777 biomedical scientists, representing a range of ages, grades and disciplines, and working for a variety of employers throughout the UK and overseas. The majority of respondents (n = 687) were current participants in the IBMS CPD scheme, but 74 replies were received from members who had not previously taken part. Half the respondents who were both scheme participants and Associate members of the IBMS and one-third of participating Fellows had yet to claim a diploma. The results showed that the IBMS CPD scheme was well respected among biomedical scientists, but many reported some difficulties in obtaining study leave and financial support to attend credited activities. Although respondents felt that an individual's own time should not be spent on CPD, activities that are performed when off duty (e.g., journal-based learning) are popular, especially among staff in younger age groups and among junior biomedical scientist grades. Respondents suggested that the scheme could be improved by provision of more resources at departmental level to allow regular participation for individual biomedical scientists. They also recommended inclusion of competency testing within CPD and a simplified diploma system. The IBMS scheme has been well received and has the potential to evolve into a good scheme to serve the profession's needs into the 21st century.
Collapse
Affiliation(s)
- S J Pitt
- School of Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool.
| | | | | |
Collapse
|
43
|
Vial C, Pitt SJ, Roberts J, Rolf MG, Mahaut-Smith MP, Evans RJ. Lack of evidence for functional ADP-activated human P2X1 receptors supports a role for ATP during hemostasis and thrombosis. Blood 2003; 102:3646-51. [PMID: 12907444 DOI: 10.1182/blood-2003-06-1963] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Purine nucleotides acting through P2 receptors play key roles in platelet signaling. The P2X1 receptor is an adenosine triphosphate (ATP)-gated ion channel that mediates a rapid calcium influx signal, but can also synergize with subsequent adenosine diphosphate (ADP)-evoked P2Y1 receptor-mediated responses and thus may contribute to platelet activation during hemostasis. Recent studies have shown that P2X1 receptors contribute to the formation of platelet thrombi, particularly under conditions of high shear stress. Based on intracellular Ca2+ measurements a previous report has suggested that a splice variant of the P2X1 receptor, P2X1del, is expressed in platelets and, in contrast to the full-length P2X1WT receptor, is activated by ADP. In the present study we show that the P2X1del receptor fails to form functional ion channels and is below the limit of detection in human platelets. Furthermore, ADP does not contribute to the rapid ionotropic P2X receptor-mediated response in platelets. These results support the notion that ATP is the principal physiologic agonist at P2X1 receptors and that it plays a role in the activation of platelets.
Collapse
Affiliation(s)
- Catherine Vial
- Department of Cell Physiology and Pharmacology, University of Leicester, University Rd, Leicester LE1 9HN, United Kingdom
| | | | | | | | | | | |
Collapse
|
44
|
Pitt SJ. Effect of psychological climate in the microbiology laboratory on the quality of service. Commun Dis Public Health 2001; 4:322-4. [PMID: 12109405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Affiliation(s)
- S J Pitt
- Liverpool John Moores University
| |
Collapse
|
45
|
Pitt SJ. Importance of staff job satisfaction in provision of a high quality microbiology service. Commun Dis Public Health 2000; 3:313-4. [PMID: 11280273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
The practice of quality assurance is a vital aspect of clinical laboratory work. Much effort has been rightly put in to setting up and running external quality assurance programmes, internal quality assurance and control, gaining accreditation with Clinical Pathology Accreditation (UK) Ltd (CPA) and undertaking clinical audit. The contribution that biomedical scientists can make at all levels to quality assurance is very important, because a good pathology service depends on teamwork. The attitude of each individual member of staff can therefore affect the quality the of a laboratory's output.
Collapse
Affiliation(s)
- S J Pitt
- School of Biomolecular Sciences, Liverpool John Moores University, Liverpool L3 3AF
| |
Collapse
|