1
|
Chernykh A, Abrahams JL, Grant OC, Kambanis L, Sumer-Bayraktar Z, Ugonotti J, Kawahara R, Corcilius L, Payne RJ, Woods RJ, Thaysen-Andersen M. Position-specific N- and O-glycosylation of the reactive center loop impacts neutrophil elastase-mediated proteolysis of corticosteroid-binding globulin. J Biol Chem 2024; 300:105519. [PMID: 38042488 PMCID: PMC10784704 DOI: 10.1016/j.jbc.2023.105519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 11/20/2023] [Accepted: 11/22/2023] [Indexed: 12/04/2023] Open
Abstract
Corticosteroid-binding globulin (CBG) delivers anti-inflammatory cortisol to inflamed tissues through proteolysis of an exposed reactive center loop (RCL) by neutrophil elastase (NE). We previously demonstrated that RCL-localized Asn347-linked N-glycans impact NE proteolysis, but a comprehensive structure-function characterization of the RCL glycosylation is still required to better understand CBG glycobiology. Herein, we first performed RCL-centric glycoprofiling of serum-derived CBG to elucidate the Asn347-glycans and then used molecular dynamics simulations to study their impact on NE proteolysis. Importantly, we also identified O-glycosylation (di/sialyl T) across four RCL sites (Thr338/Thr342/Thr345/Ser350) of serum CBG close to the NE-targeted Val344-Thr345 cleavage site. A restricted N- and O-glycan co-occurrence pattern on the RCL involving exclusively Asn347 and Thr338 glycosylation was experimentally observed and supported in silico by modeling of a CBG-GalNAc-transferase (GalNAc-T) complex with various RCL glycans. GalNAc-T2 and GalNAc-T3 abundantly expressed by liver and gall bladder, respectively, showed in vitro a capacity to transfer GalNAc (Tn) to multiple RCL sites suggesting their involvement in RCL O-glycosylation. Recombinant CBG was then used to determine roles of RCL O-glycosylation through longitudinal NE-centric proteolysis experiments, which demonstrated that both sialoglycans (disialyl T) and asialoglycans (T) decorating Thr345 inhibit NE proteolysis. Synthetic RCL O-glycopeptides expanded on these findings by showing that Thr345-Tn and Thr342-Tn confer strong and moderate protection against NE cleavage, respectively. Molecular dynamics substantiated that short Thr345-linked O-glycans abrogate NE interactions. In conclusion, we report on biologically relevant CBG RCL glycosylation events, which improve our understanding of mechanisms governing cortisol delivery to inflamed tissues.
Collapse
Affiliation(s)
- Anastasia Chernykh
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Jodie L Abrahams
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia; Glycosciences Laboratory, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom
| | - Oliver C Grant
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Lucas Kambanis
- School of Chemistry, The University of Sydney, Sydney, New South Wales, Australia; Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Zeynep Sumer-Bayraktar
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia; Glycometabolic Biochemistry Team, Cluster of Pioneering Research, RIKEN, Wako, Saitama, Japan
| | - Julian Ugonotti
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Rebeca Kawahara
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia; Institute for Glyco-core Research (iGCORE), Nagoya University, Nagoya, Japan
| | - Leo Corcilius
- School of Chemistry, The University of Sydney, Sydney, New South Wales, Australia; Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Richard J Payne
- School of Chemistry, The University of Sydney, Sydney, New South Wales, Australia; Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Robert J Woods
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Morten Thaysen-Andersen
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia; Institute for Glyco-core Research (iGCORE), Nagoya University, Nagoya, Japan.
| |
Collapse
|
2
|
Lee JH, Meyer EJ, Nenke MA, Falhammar H, Torpy DJ. Corticosteroid-binding globulin (CBG): spatiotemporal distribution of cortisol in sepsis. Trends Endocrinol Metab 2023; 34:181-190. [PMID: 36681594 DOI: 10.1016/j.tem.2023.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 01/02/2023] [Indexed: 01/22/2023]
Abstract
Corticosteroid-binding globulin (CBG) is a 50-60 kDa circulating glycoprotein with high affinity for cortisol. CBG is adapted for sepsis; its cortisol binding is reduced reversibly by pyrexia and acidaemia, and reduced irreversibly by neutrophil elastase (NE) cleavage, converting high cortisol-binding affinity CBG to a low affinity form. These characteristics allow for the targeted delivery of immunomodulatory cortisol to tissues at the time and body site where cortisol is required in sepsis and septic shock. In addition, high titer inflammatory cytokines in sepsis suppress CBG hepatic synthesis, increasing the serum free cortisol fraction. Recent clinical studies have highlighted the importance of CBG in septic shock, with CBG deficiency independently associated with mortality.
Collapse
Affiliation(s)
- Jessica H Lee
- Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Emily J Meyer
- Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia; Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia; Department of Endocrine and Diabetes, The Queen Elizabeth Hospital, Woodville South, South Australia, Australia
| | - Marne A Nenke
- Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia; Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia; Department of Endocrine and Diabetes, The Queen Elizabeth Hospital, Woodville South, South Australia, Australia
| | - Henrik Falhammar
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Department of Endocrinology, Karolinska University Hospital, Stockholm, Sweden.
| | - David J Torpy
- Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia; Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia
| |
Collapse
|
3
|
rDromaserpin: A Novel Anti-Hemostatic Serpin, from the Salivary Glands of the Hard Tick Hyalomma dromedarii. Toxins (Basel) 2021; 13:toxins13120913. [PMID: 34941750 PMCID: PMC8703697 DOI: 10.3390/toxins13120913] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/01/2021] [Accepted: 12/08/2021] [Indexed: 01/17/2023] Open
Abstract
Hemostatic disorders are caused either by platelet-related dysfunctions, defective blood coagulation, or by a combination of both, leading to an increased susceptibility to cardiovascular diseases (CVD) and other related illnesses. The unique specificity of anticoagulants from hematophagous arthropods, such as ticks, suggests that tick saliva holds great promise for discovering new treatments for these life-threatening diseases. In this study, we combined in silico and in vitro analyses to characterize the first recombinant serpin, herein called Dromaserpin, from the sialotranscriptome of the Hyalomma dromedarii tick. Our in silico data described Dromaserpin as a secreted protein of ~43 kDa with high similarities to previously characterized inhibitory serpins. The recombinant protein (rDromaserpin) was obtained as a well-structured monomer, which was tested using global blood coagulation and platelet aggregation assays. With this approach, we confirmed rDromaserpin anticoagulant activity as it significantly delayed plasma clotting in activated partial thromboplastin time and thrombin time assays. The profiling of proteolytic activity shows its capacity to inhibit thrombin in the micromolar range (0.2 to 1 μM) and in the presence of heparin this inhibition was clearly increased. It was also able to inhibit Kallikrein, FXIa and slightly FXIIa, with no significant effect on other factors. In addition, the rDromaserpin inhibited thrombin-induced platelet aggregation. Taken together, our data suggest that rDromaserpin deserves to be further investigated as a potential candidate for developing therapeutic compounds targeting disorders related to blood clotting and/or platelet aggregation.
Collapse
|
4
|
Lin HY, Song G, Lei F, Li D, Qu Y. Avian corticosteroid-binding globulin: biological function and regulatory mechanisms in physiological stress responses. Front Zool 2021; 18:22. [PMID: 33926473 PMCID: PMC8086359 DOI: 10.1186/s12983-021-00409-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 04/19/2021] [Indexed: 12/04/2022] Open
Abstract
Corticosteroid-binding globulin (CBG) is a high-affinity plasma protein that binds glucocorticoids (GCs) and regulates their biological activities. The structural and functional properties of CBG are crucial to understanding the biological actions of GCs in mediating stress responses and the underlying mechanisms. In response to stress, avian CBGs modulate the free and bound fractions of plasma corticosterone (CORT, the main GC), enabling them to mediate the physiological and behavioral responses that are fundamental for balancing the trade-off of energetic investment in reproduction, immunity, growth, metabolism and survival, including adaptations to extreme high-elevation or high-latitude environments. Unlike other vertebrates, avian CBGs substitute for sex hormone-binding globulin (SHBG) in transporting androgens and regulating their bioavailability, since birds lack an Shbg gene. The three-dimensional structures of avian and mammalian CBGs are highly conserved, but the steroid-binding site topographies and their modes of binding steroids differ. Given that CBG serves as the primary transporter of both GCs and reproductive hormones in birds, we aim to review the biological properties of avian CBGs in the context of steroid hormone transportation, stress responses and adaptation to harsh environments, and to provide insight into evolutionary adaptations in CBG functions occurred to accommodate physiological and endocrine changes in birds compared with mammals.
Collapse
Affiliation(s)
- Hai-Yan Lin
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Gang Song
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Fumin Lei
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Dongming Li
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China.
| | - Yanhua Qu
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.
| |
Collapse
|
5
|
Lovato CM, Thévenot T, Borot S, Di Martino V, Qualls CR, Urban FK, Dorin RI. Decreased maximal cortisol secretion rate in patients with cirrhosis: Relation to disease severity. JHEP Rep 2021; 3:100277. [PMID: 34027338 PMCID: PMC8121968 DOI: 10.1016/j.jhepr.2021.100277] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 02/13/2021] [Accepted: 03/07/2021] [Indexed: 02/07/2023] Open
Abstract
Background & Aims Hepatic enzymes play a major role in the metabolic elimination of cortisol, and reduced rates of cortisol clearance have been consistently observed in patients with chronic liver disease. It is less clear whether there are concomitant abnormalities of adrenocortical function in patients with cirrhosis. In the present study, we sought to assess adrenocortical function in patients with cirrhosis using measures of free cortisol appearance and elimination rates that are independent of serum concentrations of cortisol binding proteins. Methods Post hoc analysis used computer-assisted numerical and modelling methods with serial total and free cortisol concentration data to obtain rates of free cortisol appearance and elimination. Rate parameters were obtained in 114 patients with chronic liver disease, including Child-Pugh (CP) ≤8 (n = 53) and CP >8 (n = 61). Results Maximal cortisol secretion rate (CSRmax) was significantly decreased (p = 0.01) in patients with cirrhosis with CP >8 (0.28 nM/s; 95% CI 0.24–0.34) compared with those with CP ≤8 (0.39 nM/s; 95% CI 0.33–0.46), and CSRmax was negatively correlated with CP score (r = −0.19, p = 0.01). Free cortisol elimination rate was significantly (p = 0.04) decreased in the CP >8 group (0.16 ± 0.20 min−1) compared with that in the CP ≤8 group (0.21 ± 0.21 min−1), and free cortisol elimination rates were negatively correlated with CP score (r = −0.23, p = 0.01). A significant correlation between CSRmax and free cortisol elimination rate (r = 0.88, p <0.001) was observed. Conclusions CSRmax and free cortisol elimination rates were significantly reduced according to severity of cirrhosis. In contrast to stimulated total cortisol concentrations, CSRmax estimates were independent of cortisol-binding protein concentrations. Results provide additional evidence of subnormal adrenocortical function in patients with cirrhosis. Lay summary We applied numerical analytic methods to characterise adrenocortical function in patients with varying stages of chronic liver disease. We found that patients with more severe cirrhosis have decreased rate of free cortisol elimination and decreased maximal cortisol secretion rate, which is a measure of adrenocortical function. In contrast to conventional measures of adrenocortical function, those obtained using numerical methods were not affected by variation in corticosteroid binding globulin and albumin concentrations. We conclude that patients with cirrhosis demonstrate measurable abnormalities of adrenocortical function, evidence of which supports aspects of the hepatoadrenal syndrome hypothesis. Free cortisol appearance and elimination rates were obtained by computer-assisted numerical analysis. Maximal cortisol secretion rates, a measure of adrenocortical function, were inversely related to severity of cirrhosis. Variation in concentrations of cortisol binding proteins bias measures of adrenocortical function that rely on total cortisol. Chronically reduced rate of free cortisol elimination in patients with cirrhosis may contribute to the pathophysiology of subnormal adrenocortical function. Evidence of subnormal adrenocortical function supports the hepatoadrenal syndrome hypothesis.
Collapse
Key Words
- ACLF, acute-on-chronic liver failure
- ACTH, adrenocorticotrophin
- AI, adrenal insufficiency
- Adrenal insufficiency
- CBG, corticosteroid-binding globulin
- CIRCI, critical illness-related corticosteroid insufficiency
- CP, Child-Pugh
- CPR, cortisol production rate
- CRP, C-reactive protein
- CRT, corticosteroid replacement therapy
- CSR, cortisol secretion rate
- CSRbase, basal CSR (before ACTH stimulation)
- CSRmax, maximal CSR
- Computer-assisted numerical analysis
- HPA, hypothalamic–pituitary–adrenal
- HSD, hydroxysteroid dehydrogenase
- Hydrocortisone
- INR, international normalised ratio
- Liver disease
- MCR, metabolic clearance rate
- MELD, model for end-stage liver disease
- Metabolic clearance rate
- PAI, primary adrenal insufficiency
- RAI, relative adrenal insufficiency
- RCT, randomised clinical trial
- SAI, secondary adrenal insufficiency
- SCOTCH, Supplemental Corticosteroids in Cirrhotic Hypotensive Patients With Suspicion of Sepsis
- STB, standardised beta
Collapse
Affiliation(s)
- Christina M Lovato
- Department of Internal Medicine/Endocrinology, Diabetes and Metabolism, University of New Mexico Health Sciences Center, Albuquerque, NM, USA
| | - Thierry Thévenot
- Service d'Hépatologie et de Soins Intensifs Digestifs, Hôpital Universitaire Jean Minjoz, Besançon, France
| | - Sophie Borot
- Service d'Endocrinologie-Métabolisme et Diabétologie-Nutrition, Hôpital Jean Minjoz, Besançon, France
| | - Vincent Di Martino
- Service d'Hépatologie et de Soins Intensifs Digestifs, Hôpital Universitaire Jean Minjoz, Besançon, France
| | - Clifford R Qualls
- Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM, USA.,New Mexico Veterans Affairs Healthcare System, Albuquerque, NM, USA
| | - Frank K Urban
- Department of Electrical and Computer Engineering, Florida International University, Miami, FL, USA
| | - Richard I Dorin
- Department of Internal Medicine/Endocrinology, Diabetes and Metabolism, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.,New Mexico Veterans Affairs Healthcare System, Albuquerque, NM, USA
| |
Collapse
|
6
|
Lewis JG, Elder PA. Glycosylation may influence sex hormone-binding globulin measurements. Clin Chim Acta 2020; 509:95-100. [PMID: 32531254 DOI: 10.1016/j.cca.2020.06.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/06/2020] [Accepted: 06/08/2020] [Indexed: 11/30/2022]
Abstract
A discordance between sex hormone-binding globulin (SHBG) measurements by 2-site ELISAs was investigated using pairings of various "in house" SHBG antibodies together with a concordant control. The 2-site monoclonal ELISAs used the same base coat (11F11) and discordance was observed with one top coat monoclonal antibody (7H9) and also when a polyclonal SHBG antibody was paired with the basecoat antibody (11F11). Sialidase treatment of the discordant sample and purified SHBG revealed increased levels using 7H9 whereas there was no change in SHBG in the concordant sample. Conversely, following sialidase treatment, the discordant sample showed no change in SHBG measured using the other monoclonal antibody pairings whereas the SHBG levels in the concordant sample declined following sialidase using the same monoclonal antibody pairings. This implicated glycosylation as a factor in antibody recognition and synthetic peptides spanning the two N-linked and one O-linked glycosylation regions showed that SHBG recognition by monoclonal antibody 7H9 could be disrupted by a peptide spanning the O-linked glycosylation site. Hence rather than immunoassay discordance being attributed to heterophile antibodies or other circulating antibodies here it can be likely attributed to glycosylation affecting antibody recognition and hence the measurement of SHBG.
Collapse
Affiliation(s)
- John G Lewis
- Endocrinology and Steroid Laboratory, Canterbury Health Laboratories, P.O. Box 151, Christchurch 8011, New Zealand.
| | - Peter A Elder
- Endocrinology and Steroid Laboratory, Canterbury Health Laboratories, P.O. Box 151, Christchurch 8011, New Zealand
| |
Collapse
|
7
|
Ciregia F, Baiwir D, Cobraiville G, Dewael T, Mazzucchelli G, Badot V, Di Romana S, Sidiras P, Sokolova T, Durez P, Malaise MG, de Seny D. Glycosylation deficiency of lipopolysaccharide-binding protein and corticosteroid-binding globulin associated with activity and response to treatment for rheumatoid arthritis. J Transl Med 2020; 18:8. [PMID: 31907043 PMCID: PMC6945416 DOI: 10.1186/s12967-019-02188-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 12/23/2019] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Serum protein glycosylation is an area of investigation in inflammatory arthritic disorders such as rheumatoid arthritis (RA). Indeed, some studies highlighted abnormalities of protein glycosylation in RA. Considering the numerous types of enzymes, monosaccharides and glycosidic linkages, glycosylation is one of the most complex post translational modifications. By this work, we started with a preliminary screening of glycoproteins in serum from RA patients and controls. METHODS In order to isolate glycoproteins from serum, lectin wheat germ agglutinin was used and quantitative differences between patients and controls were investigated by LC-MS/MS. Consequently, we focused our attention on two glycoproteins found in this explorative phase: corticosteroid-binding globulin (CBG) and lipopolysaccharide-binding protein (LBP). The subsequent validation with immunoassays was widened to a larger number of early RA (ERA) patients (n = 90) and well-matched healthy controls (n = 90). RESULTS We observed a significant reduction of CBG and LBP glycosylation in ERA patients compared with healthy controls. Further, after 12 months of treatment, glycosylated CBG and LBP levels increased both to values comparable to those of controls. In addition, these changes were correlated with clinical parameters. CONCLUSIONS This study enables to observe that glycosylation changes of CBG and LBP are related to RA disease activity and its response to treatment.
Collapse
Affiliation(s)
- Federica Ciregia
- Laboratory of Rheumatology, GIGA-I3, University of Liège, CHU de Liège, 4000, Liège, Belgium.
| | - Dominique Baiwir
- GIGA Proteomic Facility, University of Liège, 4000, Liège, Belgium
| | - Gaël Cobraiville
- Laboratory of Rheumatology, GIGA-I3, University of Liège, CHU de Liège, 4000, Liège, Belgium
| | - Thibaut Dewael
- Laboratory of Rheumatology, GIGA-I3, University of Liège, CHU de Liège, 4000, Liège, Belgium
| | - Gabriel Mazzucchelli
- Mass Spectrometry Laboratory, System Biology and Chemical Biology, GIGA-Research, University of Liège, 4000, Liège, Belgium
| | - Valérie Badot
- Department of Rheumatology, CHU Brugmann, 1200, Brussels, Belgium
| | - Silvana Di Romana
- Department of Rheumatology, CHU Saint-Pierre, 1200, Brussels, Belgium
| | - Paschalis Sidiras
- Department of Rheumatology, Hôpital Erasme, Université Libre de Bruxelles, 1200, Brussels, Belgium
| | - Tatiana Sokolova
- Department of Rheumatology, Cliniques Universitaires Saint-Luc, Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 1200, Brussels, Belgium
| | - Patrick Durez
- Department of Rheumatology, Cliniques Universitaires Saint-Luc, Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 1200, Brussels, Belgium
| | - Michel G Malaise
- Laboratory of Rheumatology, GIGA-I3, University of Liège, CHU de Liège, 4000, Liège, Belgium
| | - Dominique de Seny
- Laboratory of Rheumatology, GIGA-I3, University of Liège, CHU de Liège, 4000, Liège, Belgium
| |
Collapse
|
8
|
Hill LA, Sumer-Bayraktar Z, Lewis JG, Morava E, Thaysen-Andersen M, Hammond GL. N-Glycosylation influences human corticosteroid-binding globulin measurements. Endocr Connect 2019; 8:1136-1148. [PMID: 31307013 PMCID: PMC6686952 DOI: 10.1530/ec-19-0242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 07/15/2019] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Discrepancies in ELISA measurements of human corticosteroid-binding globulin (CBG) using detection monoclonal antibodies that recognize an epitope (9G12) within its reactive center loop (RCL), versus an epitope (12G2) in a different location, have suggested that CBG with a proteolytically cleaved RCL exists in blood samples. We have previously been unable to verify this biochemically, and sought to determine if N-glycosylation differences account for discrepancies in ELISA measurements of CBG. METHODS AND SUBJECTS Molecular biological, biochemical and glycopeptide analyses were used to examine how N-glycosylation at specific sites, including at N347 within the RCL, affect CBG ELISA or steroid-binding capacity assay (BCA) measurements. Plasma from patients with congenital disorders of glycosylation (CDG) was also examined in these assays as examples of N-glycosylation defects. RESULTS We demonstrate that an N-glycan at N347 within the CBG RCL limits the 9G12 antibody from recognizing its epitope, whereas the 12G2 antibody reactivity is unaffected, thereby contributing to discrepancies in ELISA measurements using these two antibodies. Qualitative differences in N-glycosylation at N238 also negatively affect the steroid-binding of CBG in the absence of an N-glycan at N347 caused by a T349A substitution. Desialylation increased both ELISA measurements relative to BCA values. Similarly, plasma CBG levels in both ELISAs were much higher than BCA values in several CDG patients. CONCLUSIONS Plasma CBG measurements are influenced by variations in N-glycosylation. This is important given the increasing number of CDG defects identified recently and because N-glycosylation abnormalities are common in patients with metabolic and liver diseases.
Collapse
Affiliation(s)
- Lesley A Hill
- Departments of Cellular and Physiological Sciences and Obstetrics and Gynaecology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Zeynep Sumer-Bayraktar
- School of Life and Environmental Science, Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - John G Lewis
- Canterbury Health Laboratories, Christchurch, New Zealand
| | - Eva Morava
- Mayo Clinic, Department of Clinical Genomics, CIM, Rochester, Minnesota, USA
| | | | - Geoffrey L Hammond
- Departments of Cellular and Physiological Sciences and Obstetrics and Gynaecology, The University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
9
|
NewBG: A surrogate corticosteroid-binding globulin with an unprecedentedly high ligand release efficacy. J Struct Biol 2019; 207:169-182. [DOI: 10.1016/j.jsb.2019.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/23/2019] [Accepted: 05/15/2019] [Indexed: 11/22/2022]
|
10
|
Hill LA, Vassiliadi DA, Dimopoulou I, Anderson AJ, Boyle LD, Kilgour AHM, Stimson RH, Machado Y, Overall CM, Walker BR, Lewis JG, Hammond GL. Neutrophil elastase-cleaved corticosteroid-binding globulin is absent in human plasma. J Endocrinol 2019; 240:27-39. [PMID: 30452386 PMCID: PMC6347282 DOI: 10.1530/joe-18-0479] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 09/28/2018] [Indexed: 12/24/2022]
Abstract
Corticosteroid-binding globulin (CBG) transports glucocorticoids in blood and is a serine protease inhibitor family member. Human CBG has a reactive center loop (RCL) which, when cleaved by neutrophil elastase (NE), disrupts its steroid-binding activity. Measurements of CBG levels are typically based on steroid-binding capacity or immunoassays. Discrepancies in ELISAs using monoclonal antibodies that discriminate between intact vs RCL-cleaved CBG have been interpreted as evidence that CBG with a cleaved RCL and low affinity for cortisol exists in the circulation. We examined the biochemical properties of plasma CBG in samples with discordant ELISA measurements and sought to identify RCL-cleaved CBG in human blood samples. Plasma CBG-binding capacity and ELISA values were consistent in arterial and venous blood draining skeletal muscle, liver and brain, as well as from a tissue (adipose) expected to contain activated neutrophils in obese individuals. Moreover, RCL-cleaved CBG was undetectable in plasma from critically ill patients, irrespective of whether their ELISA measurements were concordant or discordant. We found no evidence of RCL-cleaved CBG in plasma using a heat-dependent polymerization assay, and CBG that resists immunoprecipitation with a monoclonal antibody designed to specifically recognize an intact RCL, bound steroids with a high affinity. In addition, mass spectrometry confirmed the absence of NE-cleaved CBG in plasma in which ELISA values were highly discordant. Human CBG with a NE-cleaved RCL and low affinity for steroids is absent in blood samples, and CBG ELISA discrepancies likely reflect structural differences that alter epitopes recognized by specific monoclonal antibodies.
Collapse
Affiliation(s)
- Lesley A Hill
- Departments of Cellular and Physiological Sciences and Obstetrics and Gynaecology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Dimitra A Vassiliadi
- Endocrine Unit, Second Department of Internal Medicine-Research Institute and Diabetes Center, Attiko University Hospital, Athens, Greece
| | - Ioanna Dimopoulou
- Endocrine Unit, Second Department of Internal Medicine-Research Institute and Diabetes Center, Attiko University Hospital, Athens, Greece
| | - Anna J Anderson
- BHF Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Luke D Boyle
- BHF Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Alixe H M Kilgour
- BHF Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Roland H Stimson
- BHF Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Yoan Machado
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher M Overall
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Brian R Walker
- BHF Centre for Cardiovascular Science, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - John G Lewis
- Canterbury Health Laboratories, Christchurch, New Zealand
| | - Geoffrey L Hammond
- Departments of Cellular and Physiological Sciences and Obstetrics and Gynaecology, The University of British Columbia, Vancouver, British Columbia, Canada
- Correspondence should be addressed to G L Hammond:
| |
Collapse
|