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Fedosov SN, Nexo E, Heegaard CW. Kinetics of Cellular Cobalamin Uptake and Conversion: Comparison of Aquo/Hydroxocobalamin to Cyanocobalamin. Nutrients 2024; 16:378. [PMID: 38337663 PMCID: PMC10857013 DOI: 10.3390/nu16030378] [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: 12/22/2023] [Revised: 01/21/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Cyanocobalamin (CNCbl) and aquo/hydroxocobalamin (HOCbl) are the forms of vitamin B12 that are most commonly used for supplementation. They are both converted to methylcobalamin (MeCbl) and 5'-deoxyadenosylcobalamin (AdoCbl), which metabolize homocysteine and methylmalonic acid, respectively. Here, we compare the kinetics of uptake and the intracellular transformations of radiolabeled CNCbl vs. HOCbl in HeLa cells. More HOCbl was accumulated over 4-48 h, but further extrapolation indicated similar uptake (>90%) for both vitamin forms. The initially synthesized coenzyme was MeCbl, which noticeably exceeded AdoCbl during 48 h. Yet, the synthesis of AdoCbl accelerated, and the predicted final levels of Cbls were MeCbl ≈ AdoCbl ≈ 40% and HOCbl ≈ 20%. The designed kinetic model revealed the same patterns of the uptake and turnover for CNCbl and HOCbl, apart from two steps. First, the "activating" intracellular processing of the internalized HOCbl was six-fold faster. Second, the detachment rates from the cell surface (when the "excessive" Cbl-molecules were refluxed into the external medium) related as 4:1 for CNCbl vs. HOCbl. This gave a two-fold faster cellular accumulation and processing of HOCbl vs. CNCbl. In medical terms, our data suggest (i) an earlier response to the treatment of Cbl-deficiency with HOCbl, and (ii) the manifestation of a successful treatment initially as a decrease in homocysteine.
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Affiliation(s)
- Sergey N. Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark;
- Department of Clinical Medicine/Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark;
| | - Ebba Nexo
- Department of Clinical Medicine/Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark;
| | - Christian W. Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark;
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Eduin B, Roubille C, Badiou S, Cristol JP, Fesler P. Association between Elevated Plasma Vitamin B12 and Short-Term Mortality in Elderly Patients Hospitalized in an Internal Medicine Unit. Int J Clin Pract 2023; 2023:6652671. [PMID: 38146346 PMCID: PMC10749720 DOI: 10.1155/2023/6652671] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 10/14/2023] [Accepted: 11/25/2023] [Indexed: 12/27/2023] Open
Abstract
Background The prognostic value of vitamin B12 blood levels remains controversial. An association between elevated vitamin B12 and mortality has been reported, particularly among elderly patients with cancers and liver or blood diseases. The present study explored the relationship between mortality and elevated vitamin B12 levels in a population of unscheduled inpatients in an internal medicine unit. Methods This retrospective observational analysis was conducted between August 2014 and December 2018. We compared 165 patients with elevated plasma vitamin B12 levels (>600 pmol/l) with a random sample of 165 patients with normal B12 levels who were hospitalized during the same period. Demographic, clinical, and biological characteristics were assessed during hospitalization. The primary endpoint was all-cause death at 1 year. Results Patients with elevated B12 were younger, with a lower body mass index and lower plasma albumin than those with normal B12 (75 ± 16 years vs 79 ± 13 years, p = 0.047; 23 ± 5 vs 26 ± 7 kg/m2, p < 0.001; and 33 ± 5 vs 35 ± 5 g/l, p < 0.001, respectively). The prevalence of auto-immune disease and referral from an intensive care unit was higher among patients with elevated B12 (11% vs 5%, p = 0.043 and 36% vs 10%, p < 0.001, respectively). After 1 year of follow-up, 64 (39%) patients with elevated B12 had died compared to 43 (26%) patients with normal B12 (p = 0.018). Multivariate analysis using the Cox proportional hazards regression model adjusted for age, gender, body mass index, intensive care unit hospitalization, albumin level, and the presence of solid cancer or autoimmune disease revealed elevated B12 to be associated with a significant risk of death in the first year of follow-up (hazard ratio: 1.71 [1.08-2.7], p = 0.022). Conclusion Elevated B12 is an early warning indicator of increased short-term mortality, such as independently of age, cancer, or comorbidities, in patients hospitalized in an internal medicine department.
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Affiliation(s)
- Benjamin Eduin
- Department of Internal Medicine, University Hospital of Montpellier, Montpellier, France
| | - Camille Roubille
- Department of Internal Medicine, University Hospital of Montpellier, Montpellier, France
- PhyMedExp, University of Montpellier, INSERM, CNRS, University Hospital of Montpellier, Montpellier, France
| | - Stéphanie Badiou
- PhyMedExp, University of Montpellier, INSERM, CNRS, University Hospital of Montpellier, Montpellier, France
- Department of Biochemistry and Hormonology, University Hospital of Montpellier, Montpellier, France
| | - Jean Paul Cristol
- PhyMedExp, University of Montpellier, INSERM, CNRS, University Hospital of Montpellier, Montpellier, France
- Department of Biochemistry and Hormonology, University Hospital of Montpellier, Montpellier, France
| | - Pierre Fesler
- Department of Internal Medicine, University Hospital of Montpellier, Montpellier, France
- PhyMedExp, University of Montpellier, INSERM, CNRS, University Hospital of Montpellier, Montpellier, France
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Warfel HC, Wilcoxen TE. Lack of vitamin B12 impairs innate and adaptive immunity of Cuban tree frog (Osteopilus septentrionalis) tadpoles. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2023; 339:878-886. [PMID: 37522473 DOI: 10.1002/jez.2738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 07/10/2023] [Accepted: 07/12/2023] [Indexed: 08/01/2023]
Abstract
Vitamin B12 is a micronutrient required by a variety of organisms for healthy cellular functioning. Despite the systemic effects observed in cases of B12 deficiency, relatively little is known about how vitamin B12 affects immune health, especially in amphibians, which are declining at unprecedented rates. In this study, we tested how supplementing an algae diet with B12 affects the innate and adaptive immunity of Cuban tree frog (Osteopilus septentrionalis) tadpoles. We found that innate immunity, as measured by a bacterial killing assay, was significantly more robust in B12-supplemented tadpoles than control tadpoles, but no significant differences were found in natural antibody production or hematocrit between groups. Adaptive immunity, as measured by Aeromonas hydrophila-specific IgY antibodies, was significantly greater in tadpoles challenged with A. hydrophila and supplemented with B12 than in control tadpoles, those only challenged with A. hydrophila, and those only given B12. Our results suggest that vitamin B12 is an important factor in maintaining a functional immune system in tadpoles, which may also be true for all vertebrates.
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Affiliation(s)
- Hannah C Warfel
- School of Biological Sciences, Illinois State University, Normal, Illinois, USA
- Department of Biology, Millikin University, Decatur, Illinois, USA
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Toft A, Sjödin S, Simonsen AH, Ejlerskov P, Roos P, Musaeus CS, Henriksen EE, Nielsen TT, Brinkmalm A, Blennow K, Zetterberg H, Nielsen JE. Endo-lysosomal protein concentrations in CSF from patients with frontotemporal dementia caused by CHMP2B mutation. ALZHEIMER'S & DEMENTIA (AMSTERDAM, NETHERLANDS) 2023; 15:e12402. [PMID: 36815874 PMCID: PMC9936136 DOI: 10.1002/dad2.12402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 01/02/2023] [Accepted: 01/12/2023] [Indexed: 02/19/2023]
Abstract
Introduction Increasing evidence implicates proteostatic dysfunction as an early event in the development of frontotemporal dementia (FTD). This study aimed to explore potential cerebrospinal fluid (CSF) biomarkers associated with the proteolytic systems in genetic FTD caused by CHMP2B mutation. Methods Combining solid-phase extraction and parallel reaction monitoring mass spectrometry, a panel of 47 peptides derived from 20 proteins was analyzed in CSF from 31 members of the Danish CHMP2B-FTD family. Results Compared with family controls, mutation carriers had significantly higher levels of complement C9, lysozyme and transcobalamin II, and lower levels of ubiquitin, cathepsin B, and amyloid precursor protein. Discussion Lower CSF ubiquitin concentrations in CHMP2B mutation carriers indicate that ubiquitin levels relate to the specific disease pathology, rather than all-cause neurodegeneration. Increased lysozyme and complement proteins may indicate innate immune activation. Altered levels of amyloid precursor protein and cathepsins have previously been associated with impaired lysosomal proteolysis in FTD. Highlights CSF markers of proteostasis were explored in CHMP2B-mediated frontotemporal dementia (FTD).31 members of the Danish CHMP2B-FTD family were included.We used solid-phase extraction and parallel reaction monitoring mass spectrometry.Six protein levels were significantly altered in CHMP2B-FTD compared with controls.Lower CSF ubiquitin levels in patients suggest association with disease mechanisms.
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Affiliation(s)
- Anders Toft
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Simon Sjödin
- Laboratory of Clinical ChemistrySahlgrenska University HospitalGothenburgSweden
| | - Anja Hviid Simonsen
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Patrick Ejlerskov
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Peter Roos
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Christian Sandøe Musaeus
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Emil Elbæk Henriksen
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Troels Tolstrup Nielsen
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
| | - Ann Brinkmalm
- Clinical Neurochemistry LaboratorySahlgrenska University HospitalMölndalSweden
| | - Kaj Blennow
- Clinical Neurochemistry LaboratorySahlgrenska University HospitalMölndalSweden,Department of Psychiatry and NeurochemistryInstitute of Neuroscience and Physiologythe Sahlgrenska Academy at the University of GothenburgMölndalSweden
| | - Henrik Zetterberg
- Clinical Neurochemistry LaboratorySahlgrenska University HospitalMölndalSweden,Department of Psychiatry and NeurochemistryInstitute of Neuroscience and Physiologythe Sahlgrenska Academy at the University of GothenburgMölndalSweden,Department of Neurodegenerative DiseaseUCL Institute of NeurologyQueen SquareLondonUK,UK Dementia Research Institute at UCLLondonUK,Hong Kong Center for Neurodegenerative DiseasesClear Water BayHong KongChina
| | - Jørgen Erik Nielsen
- Neurogenetics Clinic & Research LabDanish Dementia Research CentreRigshospitaletCopenhagenDenmark
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Linagliptin treatment is associated with altered cobalamin (VitB12) homeostasis in mice and humans. Sci Rep 2023; 13:601. [PMID: 36635409 PMCID: PMC9837112 DOI: 10.1038/s41598-023-27648-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 01/05/2023] [Indexed: 01/14/2023] Open
Abstract
Linagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor used for the treatment of type 2 diabetes, with additional beneficial effects for the kidney. Treatment of mice with linagliptin revealed increased storage of cobalamin (Cbl, Vitamin B12) in organs if a standard Cbl diet (30 µg Cbl/kg chow) is given. In order to translate these findings to humans, we determined methylmalonic acid (MMA), a surrogate marker of functional Cbl homeostasis, in human plasma and urine samples (n = 1092) from baseline and end of trial (6 months after baseline) of the previously completed MARLINA-T2D clinical trial. We found that individuals with medium Cbl levels (MMA between 50 and 270 nmol/L for plasma, 0.4 and 3.5 µmol/mmol creatinine for urine, at baseline and end of trial) exhibited higher MMA values at the end of study in placebo compared with linagliptin. Linagliptin might inhibit the N-terminal degradation of the transcobalamin receptor CD320, which is necessary for uptake of Cbl into endothelial cells. Because we demonstrate that linagliptin led to increased organ levels of Cbl in mice, sustained constant medium MMA levels in humans, and inhibited CD320 processing by DPP-4 in-vitro, we speculate that linagliptin promotes intra-cellular uptake of Cbl by prolonging half-life of CD320.
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Esser AJ, Mukherjee S, Dereven‘kov IA, Makarov SV, Jacobsen DW, Spiekerkoetter U, Hannibal L. Versatile Enzymology and Heterogeneous Phenotypes in Cobalamin Complementation Type C Disease. iScience 2022; 25:104981. [PMID: 36105582 PMCID: PMC9464900 DOI: 10.1016/j.isci.2022.104981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Nutritional deficiency and genetic errors that impair the transport, absorption, and utilization of vitamin B12 (B12) lead to hematological and neurological manifestations. The cblC disease (cobalamin complementation type C) is an autosomal recessive disorder caused by mutations and epi-mutations in the MMACHC gene and the most common inborn error of B12 metabolism. Pathogenic mutations in MMACHC disrupt enzymatic processing of B12, an indispensable step before micronutrient utilization by the two B12-dependent enzymes methionine synthase (MS) and methylmalonyl-CoA mutase (MUT). As a result, patients with cblC disease exhibit plasma elevation of homocysteine (Hcy, substrate of MS) and methylmalonic acid (MMA, degradation product of methylmalonyl-CoA, substrate of MUT). The cblC disorder manifests early in childhood or in late adulthood with heterogeneous multi-organ involvement. This review covers current knowledge on the cblC disease, structure–function relationships of the MMACHC protein, the genotypic and phenotypic spectra in humans, experimental disease models, and promising therapies.
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Diagnostic and Therapeutic Perspectives Associated to Cobalamin-Dependent Metabolism and Transcobalamins’ Synthesis in Solid Cancers. Nutrients 2022; 14:nu14102058. [PMID: 35631199 PMCID: PMC9145230 DOI: 10.3390/nu14102058] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 05/11/2022] [Indexed: 02/01/2023] Open
Abstract
Cobalamin or vitamin B12 (B12) is a cofactor for methionine synthase and methylmalonyl-CoA mutase, two enzymes implicated in key pathways for cell proliferation: methylation, purine synthesis, succinylation and ATP production. Ensuring these functions in cancer cells therefore requires important cobalamin needs and its uptake through the transcobalamin II receptor (TCII-R). Thus, both the TCII-R and the cobalamin-dependent metabolic pathways constitute promising therapeutic targets to inhibit cancer development. However, the link between cobalamin and solid cancers is not limited to cellular metabolism, as it also involves the circulating transcobalamins I and II (TCI or haptocorrin and TCII) carrier proteins, encoded by TCN1 and TCN2, respectively. In this respect, elevations of B12, TCI and TCII concentrations in plasma are associated with cancer onset and relapse, and with the presence of metastases and worse prognosis. In addition, TCN1 and TCN2 overexpressions are associated with chemoresistance and a proliferative phenotype, respectively. Here we review the involvement of cobalamin and transcobalamins in cancer diagnosis and prognosis, and as potential therapeutic targets. We further detail the relationship between cobalamin-dependent metabolic pathways in cancer cells and the transcobalamins’ abundancies in plasma and tumors, to ultimately hypothesize screening and therapeutic strategies linking these aspects.
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Corin: A Key Mediator in Sodium Homeostasis, Vascular Remodeling, and Heart Failure. BIOLOGY 2022; 11:biology11050717. [PMID: 35625445 PMCID: PMC9138375 DOI: 10.3390/biology11050717] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 05/01/2022] [Accepted: 05/05/2022] [Indexed: 12/11/2022]
Abstract
Simple Summary Atrial natriuretic peptide (ANP) is an important hormone that regulates many physiological and pathological processes, including electrolyte and body fluid balance, blood volume and pressure, cardiac channel activity and function, inflammatory response, lipid metabolism, and vascular remodeling. Corin is a transmembrane serine protease that activates ANP. Variants in the CORIN gene are associated with cardiovascular disease, including hypertension, cardiac hypertrophy, atrial fibrillation, heart failure, and preeclampsia. The current data indicate a key role of corin-mediated ANP production and signaling in the maintenance of cardiovascular homeostasis. In this review, we discuss the latest findings regarding the molecular and cellular mechanisms underlying the role of corin in sodium homeostasis, uterine spiral artery remodeling, and heart failure. Abstract Atrial natriuretic peptide (ANP) is a crucial element of the cardiac endocrine function that promotes natriuresis, diuresis, and vasodilation, thereby protecting normal blood pressure and cardiac function. Corin is a type II transmembrane serine protease that is highly expressed in the heart, where it converts the ANP precursor to mature ANP. Corin deficiency prevents ANP activation and causes hypertension and heart disease. In addition to the heart, corin is expressed in other tissues, including those of the kidney, skin, and uterus, where corin-mediated ANP production and signaling act locally to promote sodium excretion and vascular remodeling. These results indicate that corin and ANP function in many tissues via endocrine and autocrine mechanisms. In heart failure patients, impaired natriuretic peptide processing is a common pathological mechanism that contributes to sodium and body fluid retention. In this review, we discuss most recent findings regarding the role of corin in non-cardiac tissues, including the kidney and skin, in regulating sodium homeostasis and body fluid excretion. Moreover, we describe the molecular mechanisms underlying corin and ANP function in supporting orderly cellular events in uterine spiral artery remodeling. Finally, we assess the potential of corin-based approaches to enhance natriuretic peptide production and activity as a treatment of heart failure.
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Hannibal L, Jacobsen DW. Intracellular processing of vitamin B 12 by MMACHC (CblC). VITAMINS AND HORMONES 2022; 119:275-298. [PMID: 35337623 DOI: 10.1016/bs.vh.2022.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Vitamin B12 (cobalamin, Cbl, B12) is a water-soluble micronutrient synthesized exclusively by a group of microorganisms. Human beings are unable to make B12 and thus obtain the vitamin via intake of animal products, fermented plant-based foods or supplements. Vitamin B12 obtained from the diet comprises three major chemical forms, namely hydroxocobalamin (HOCbl), methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl). The most common form of B12 present in supplements is cyanocobalamin (CNCbl). Yet, these chemical forms cannot be utilized directly as they come, but instead, they undergo chemical processing by the MMACHC protein, also known as CblC. Processing of dietary B12 by CblC involves removal of the upper-axial ligand (beta-ligand) yielding the one-electron reduced intermediate cob(II)alamin. Newly formed cob(II)alamin undergoes trafficking and delivery to the two B12-dependent enzymes, cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MUT). The catalytic cycles of MS and MUT incorporate cob(II)alamin as a precursor to regenerate the coenzyme forms MeCbl and AdoCbl, respectively. Mutations and epimutations in the MMACHC gene result in cblC disease, the most common inborn error of B12 metabolism, which manifests with combined homocystinuria and methylmalonic aciduria. Elevation of metabolites homocysteine and methylmalonic acid occurs because the lack of an active CblC blocks formation of the indispensable precursor cob(II)alamin that is necessary to activate MS and MUT. Thus, in patients with cblC disease, vitamin B12 is absorbed and present in circulation in normal to high concentrations, yet, cells are unable to make use of it. Mutations in seemingly unrelated genes that modify MMACHC gene expression also result in clinical phenotypes that resemble cblC disease. We review current knowledge on structural and functional aspects of intracellular processing of vitamin B12 by the versatile protein CblC, its partners and possible regulators.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany.
| | - Donald W Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
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Bloch JS, Sequeira JM, Ramírez AS, Quadros EV, Locher KP. Generation of nanobodies targeting the human, transcobalamin-mediated vitamin B 12 uptake route. FASEB J 2022; 36:e22222. [PMID: 35218573 DOI: 10.1096/fj.202101376rr] [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: 09/03/2021] [Revised: 02/04/2022] [Accepted: 02/10/2022] [Indexed: 11/11/2022]
Abstract
Cellular uptake of vitamin B12 in humans is mediated by the endocytosis of the B12 carrier protein transcobalamin (TC) via its cognate cell surface receptor TCblR, encoded by the CD320 gene. Because CD320 expression is associated with the cell cycle and upregulated in highly proliferating cells including cancer cells, this uptake route is a potential target for cancer therapy. We developed and characterized four camelid nanobodies that bind holo-TC (TC in complex with B12 ) or the interface of the human holo-TC:TCblR complex with nanomolar affinities. We determined X-ray crystal structures of these nanobodies bound to holo-TC:TCblR, which enabled us to map their binding epitopes. When conjugated to the model toxin saporin, three of our nanobodies caused growth inhibition of HEK293T cells and therefore have the potential to inhibit the growth of human cancer cells. We visualized the cellular binding and endocytic uptake of the most potent nanobody (TC-Nb4) using fluorescent light microscopy. The co-crystal structure of holo-TC:TCblR with another nanobody (TC-Nb34) revealed novel features of the interface of TC and the LDLR-A1 domain of TCblR, rationalizing the decrease in the affinity of TC-B12 binding caused by the Δ88 mutation in CD320.
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Affiliation(s)
- Joël S Bloch
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
| | - Jeffrey M Sequeira
- Department of Medicine, SUNY-Downstate Medical Center, Brooklyn, New York, USA
| | - Ana S Ramírez
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
| | - Edward V Quadros
- Department of Medicine, SUNY-Downstate Medical Center, Brooklyn, New York, USA
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
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Chen Y, Gu X, Zhang Y, Zhang X, Zhang C, Liu M, Sun S, Dong N, Wu Q. CD320 expression and apical membrane targeting in renal and intestinal epithelial cells. Int J Biol Macromol 2022; 201:85-92. [PMID: 34998874 DOI: 10.1016/j.ijbiomac.2021.12.158] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/21/2021] [Accepted: 12/24/2021] [Indexed: 02/06/2023]
Abstract
Vitamin B12 is an essential nutrient acquired via dietary intake. Receptor-mediated endocytosis is a key mechanism in vitamin B12 absorption, cellular uptake, and reabsorption. CD320 is a type I transmembrane protein responsible for cellular uptake of vitamin B12 in peripheral tissues. In this study, we examined segmental distribution and cellular expression of CD320 in mouse kidneys and intestines. We show that CD320 is expressed on the luminal surface in the small intestine and in proximal tubules in the kidney, suggesting that, in addition to its role in vitamin B12 uptake in peripheral tissues, CD320 may participate in vitamin B12 absorption in the small intestine and reabsorption in the kidney. Moreover, we show that an amino acid motif, DSSDE, in the second low-density lipoprotein receptor class A domain of CD320 is a key apical membrane targeting signal in both renal and intestinal epithelial cells. Mutations or deletion of this motif abolish the specific apical membrane expression of CD320 in polarized Madin-Darby canine kidney cells and human colon cancer-derived Caco-2 cells. In short-hairpin RNA-based gene knockdown experiments, we show that the apical membrane targeting of CD320 is mediated by a Rab11a-dependent mechanism. These results extend our knowledge regarding the cell biology of CD320 and its role in vitamin B12 metabolism.
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Affiliation(s)
- Yue Chen
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Xiabing Gu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Yikai Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Xianrui Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Ce Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Meng Liu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Shijin Sun
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Ningzheng Dong
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Qingyu Wu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China.
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Kobalamina – właściwości biomedyczne i niedobór w ujęciu biochemicznym. POSTEP HIG MED DOSW 2021. [DOI: 10.2478/ahem-2021-0004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstrakt
Kobalamina (witamina B12) jest rozpuszczalnym w wodzie związkiem organicznym, zaliczanym do witamin grupy B. Złożona budowa i polarność cząsteczki witaminy B12 sprawiają, że do jej prawidłowego wykorzystania i przemian w organizmie człowieka niezbędny jest udział wyspecjalizowanych białek. Głównym źródłem kobalaminy człowieka jest pokarm pochodzenia zwierzęcego. Ze względu na rezerwy tkankowe tej witaminy, jej niedobór ujawnia się dopiero po kilku latach niewystarczającej podaży z pożywieniem. Badania przesiewowe pod kątem deficytu kobalaminy są jednak uzasadnione u osób z czynnikami ryzyka hipokobalaminemii, takimi jak: stan po resekcji żołądka lub jelita cienkiego, dieta wegańska, długotrwałe stosowanie metforminy, antagonistów receptora histaminowego H2 oraz leków z grupy inhibitorów pompy protonowej, a także podeszły wiek.
Witamina B12 jako kofaktor enzymatyczny uczestniczy w licznych przemianach wewnątrzmitochondrialnych oraz w syntezie metioniny, niezbędnej do powstania S-adenozylometioniny istotnej w procesie metylacji cząsteczek biologicznie czynnych. Przez powiązania metaboliczne z kwasem foliowym kobalamina wpływa na proces syntezy DNA i podział komórki. Obecnie coraz częściej zwraca się uwagę na potencjalny udział niedoboru witaminy B12 w patogenezie chorób neurodegeneracyjnych, a także nowotworowych. Niedobór kobalaminy na poziomie molekularnym destabilizuje genom komórek, zwiększając ryzyko ich złośliwej transformacji. Jednak u osób z chorobą nowotworową lub obciążonych ryzykiem jej rozwoju witamina B12 może nasilać ekspansję komórek neoplastycznych.
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13
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O'Logbon J, Crook M, Steed D, Harrington DJ, Sobczyńska-Malefora A. Ethnicity influences total serum vitamin B 12 concentration: a study of Black, Asian and White patients in a primary care setting. J Clin Pathol 2021; 75:598-604. [PMID: 33952588 DOI: 10.1136/jclinpath-2021-207519] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/21/2021] [Accepted: 04/06/2021] [Indexed: 11/03/2022]
Abstract
AIMS A growing body of evidence suggests that ethnicity and race influence vitamin B12 metabolism and status yet clinical awareness of this is poor, causing doubts regarding diagnosis and treatment. Moreover, deficiency and insufficiency cut-offs are universally applied for this test in most diagnostic settings. The objective of this study was to assess serum vitamin B12 concentrations in Black, Asian and White primary care patients in London, UK, particularly in patients of Black or Black British ethnic origin and establish if there is a need for specific reference ranges. METHODS Serum B12 results from 49 414 patients were processed between January 2018 and November 2019 using the Architect assay (Abbott Diagnostics) at St. Thomas' Hospital, London, UK. Age, sex and ethnicity data were collected from the laboratory Health Informatics Team. RESULTS Black patients (n=13 806) were found to have significantly higher serum vitamin B12 concentration across all age groups and both sexes, especially Nigerian patients (median B12 505 pmol/L,IQR: 362-727, n=891), compared with Asian and White ethnic groups (p<0.001). Binary logistic regression analysis revealed that the Black or Black British ethnic group had the strongest association with elevated serum B12 (>652 pmol/L) (adjusted OR 3.38, 95% CI 3.17 to 3.61, p<0.0001). CONCLUSIONS It is likely that a combination of genetic and acquired/environmental factors are responsible for the ethnic differences in serum B12. This suggests that there is a need for ethnic-specific reference ranges with indications for the incorporation of age and sex too.
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Affiliation(s)
- Jessica O'Logbon
- GKT School of Medicine, King's College London Faculty of Life Sciences and Medicine, London, UK jessica.o'
| | - Martin Crook
- Clinical Biochemistry and Metabolic Medicine, Guy's, St Thomas' Trust, London, UK.,Clinical Biochemistry and Metabolic Medicine, Lewisham and Greenwich Trust, London, UK.,Hon Professor in Biochemical Medicine, King's College London, London, UK
| | - David Steed
- Viapath Informatics, Viapath, Francis House, St Thomas' Hospital, London, UK
| | - Dominic Jon Harrington
- Faculty of Life Sciences and Medicine, King's College London, London, UK.,The Nutristasis Unit, Viapath, St. Thomas' Hospital, London, UK
| | - Agata Sobczyńska-Malefora
- Faculty of Life Sciences and Medicine, King's College London, London, UK.,The Nutristasis Unit, Viapath, St. Thomas' Hospital, London, UK
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The avian retroviral receptor Tva mediates the uptake of transcobalamin bound vitamin B12 (cobalamin). J Virol 2021; 95:JVI.02136-20. [PMID: 33504597 PMCID: PMC8103681 DOI: 10.1128/jvi.02136-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The Avian sarcoma and leukosis viruses (ASLVs) are important chicken pathogens. Some of the virus subgroups, including ASLV-A and K, utilize the Tva receptor for cell entrance. Though Tva was identified three decades ago, its physiological function remains unknown. Previously, we have noted an intriguing resemblance and orthology between the chicken gene coding for Tva and the human gene coding for CD320, a receptor involved in cellular uptake of transcobalamin (TC) in complex with vitamin B12/cobalamin (Cbl).Here we show that both the transmembrane and the glycosylphosphatidylinositol (GPI)-anchored form of Tva in the chicken cell line DF-1 promotes the uptake of Cbl with help of expressed and purified chicken TC. The uptake of TC-Cbl complex was monitored using an isotope- or fluorophore-labeled Cbl. We show that (i) TC-Cbl is internalized in chicken cells; and (ii) the uptake is lower in the Tva-knockout cells and higher in Tva-overexpressing cells when compared with wild type chicken cells. The relation between physiological function of Tva and its role in infection was elaborated by showing that infection with ASLV subgroups (targeting Tva) impairs the uptake of TC-Cbl, while this is not the case for cells infected with ASLV-B (not recognized by Tva). In addition, exposure of the cells to a high concentration of TC-Cbl alleviates the infection with Tva-dependent ASLV.IMPORTANCE: We demonstrate that the ASLV receptor Tva participates in the physiological uptake of TC-Cbl, because the viral infection suppresses the uptake of Cbl and vice versa. Our results pave the road for future studies addressing the issues: (i) whether a virus infection can be inhibited by TC-Cbl complexes in vivo; and (ii) whether any human virus employs the human TC-Cbl receptor CD320. In broader terms, our study sheds light on the intricate interplay between physiological roles of cellular receptors and their involvement in virus infection.
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