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Hart NJ, Weber C, Price N, Banuelos A, Schultz M, Huey B, Harnois E, Gibson C, Steyn LV, Papas KK, Lynch RM. Insulinoma-derived pseudo-islets for diabetes research. Am J Physiol Cell Physiol 2021; 321:C247-C256. [PMID: 34106785 DOI: 10.1152/ajpcell.00466.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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: 11/22/2022]
Abstract
The islets of Langerhans of the pancreas are the primary endocrine organ responsible for regulating whole body glucose homeostasis. The use of isolated primary islets for research development and training requires organ resection, careful digestion, and isolation of the islets from nonendocrine tissue. This process is time consuming, expensive, and requires substantial expertise. For these reasons, we sought to develop a more rapidly obtainable and consistent model system with characteristic islet morphology and function that could be employed to train personnel and better inform experiments prior to using isolated rodent and human islets. Immortalized β cell lines reflect several aspects of primary β cells, but cell propagation in monolayer cell culture limits their usefulness in several areas of research, which depend on islet morphology and/or functional assessment. In this manuscript, we describe the propagation and characterization of insulinoma pseudo-islets (IPIs) from a rat insulinoma cell line INS832/3. IPIs were generated with an average diameter of 200 μm, consistent with general islet morphology. The rates of oxygen consumption and mitochondrial oxidation-reduction changes in response to glucose and metabolic modulators were similar to isolated rat islets. In addition, the dynamic insulin secretory patterns of IPIs were similar to primary rat islets. Thus, INS832/3-derived IPIs provide a valuable and convenient model for accelerating islet and diabetes research.
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Affiliation(s)
| | - Craig Weber
- Department of Physiology, University of Arizona, Tucson, Arizona
| | - Nicholas Price
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Alma Banuelos
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Madison Schultz
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Barry Huey
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Emily Harnois
- Department of Physiology, University of Arizona, Tucson, Arizona
| | - Cyonna Gibson
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Leah V Steyn
- Department of Surgery, University of Arizona, Tucson, Arizona
| | - Klearchos K Papas
- Department of Surgery, University of Arizona, Tucson, Arizona.,Department of Biomedical Engineering, University of Arizona, Tucson, Arizona.,The BIO5 Institute, University of Arizona, Tucson, Arizona
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson, Arizona.,Department of Biomedical Engineering, University of Arizona, Tucson, Arizona.,The BIO5 Institute, University of Arizona, Tucson, Arizona
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2
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Pendleton AL, Wesolowski SR, Regnault TRH, Lynch RM, Limesand SW. Dimming the Powerhouse: Mitochondrial Dysfunction in the Liver and Skeletal Muscle of Intrauterine Growth Restricted Fetuses. Front Endocrinol (Lausanne) 2021; 12:612888. [PMID: 34079518 PMCID: PMC8165279 DOI: 10.3389/fendo.2021.612888] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 04/22/2021] [Indexed: 11/14/2022] Open
Abstract
Intrauterine growth restriction (IUGR) of the fetus, resulting from placental insufficiency (PI), is characterized by low fetal oxygen and nutrient concentrations that stunt growth rates of metabolic organs. Numerous animal models of IUGR recapitulate pathophysiological conditions found in human fetuses with IUGR. These models provide insight into metabolic dysfunction in skeletal muscle and liver. For example, cellular energy production and metabolic rate are decreased in the skeletal muscle and liver of IUGR fetuses. These metabolic adaptations demonstrate that fundamental processes in mitochondria, such as substrate utilization and oxidative phosphorylation, are tempered in response to low oxygen and nutrient availability. As a central metabolic organelle, mitochondria coordinate cellular metabolism by coupling oxygen consumption to substrate utilization in concert with tissue energy demand and accretion. In IUGR fetuses, reducing mitochondrial metabolic capacity in response to nutrient restriction is advantageous to ensure fetal survival. If permanent, however, these adaptations may predispose IUGR fetuses toward metabolic diseases throughout life. Furthermore, these mitochondrial defects may underscore developmental programming that results in the sequela of metabolic pathologies. In this review, we examine how reduced nutrient availability in IUGR fetuses impacts skeletal muscle and liver substrate catabolism, and discuss how enzymatic processes governing mitochondrial function, such as the tricarboxylic acid cycle and electron transport chain, are regulated. Understanding how deficiencies in oxygen and substrate metabolism in response to placental restriction regulate skeletal muscle and liver metabolism is essential given the importance of these tissues in the development of later lifer metabolic dysfunction.
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Affiliation(s)
- Alexander L. Pendleton
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, AZ, United States
| | - Stephanie R. Wesolowski
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, United States
| | | | - Ronald M. Lynch
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, AZ, United States
| | - Sean W. Limesand
- School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, AZ, United States
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3
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Pendleton AL, Antolic AT, Kelly AC, Davis MA, Camacho LE, Doubleday K, Anderson MJ, Langlais PR, Lynch RM, Limesand SW. Lower oxygen consumption and Complex I activity in mitochondria isolated from skeletal muscle of fetal sheep with intrauterine growth restriction. Am J Physiol Endocrinol Metab 2020; 319:E67-E80. [PMID: 32396498 PMCID: PMC7468780 DOI: 10.1152/ajpendo.00057.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 01/25/2023]
Abstract
Fetal sheep with placental insufficiency-induced intrauterine growth restriction (IUGR) have lower hindlimb oxygen consumption rates (OCRs), indicating depressed mitochondrial oxidative phosphorylation capacity in their skeletal muscle. We hypothesized that OCRs are lower in skeletal muscle mitochondria from IUGR fetuses, due to reduced electron transport chain (ETC) activity and lower abundances of tricarboxylic acid (TCA) cycle enzymes. IUGR sheep fetuses (n = 12) were created with mid-gestation maternal hyperthermia and compared with control fetuses (n = 12). At 132 ± 1 days of gestation, biceps femoris muscles were collected, and the mitochondria were isolated. Mitochondria from IUGR muscle have 47% lower State 3 (Complex I-dependent) OCRs than controls, whereas State 4 (proton leak) OCRs were not different between groups. Furthermore, Complex I, but not Complex II or IV, enzymatic activity was lower in IUGR fetuses compared with controls. Proteomic analysis (n = 6/group) identified 160 differentially expressed proteins between groups, with 107 upregulated and 53 downregulated mitochondria proteins in IUGR fetuses compared with controls. Although no differences were identified in ETC subunit protein abundances, abundances of key TCA cycle enzymes [isocitrate dehydrogenase (NAD+) 3 noncatalytic subunit β (IDH3B), succinate-CoA ligase ADP-forming subunit-β (SUCLA2), and oxoglutarate dehydrogenase (OGDH)] were lower in IUGR mitochondria. IUGR mitochondria had a greater abundance of a hypoxia-inducible protein, NADH dehydrogenase 1α subcomplex 4-like 2, which is known to incorporate into Complex I and lower Complex I-mediated NADH oxidation. Our findings show that mitochondria from IUGR skeletal muscle adapt to hypoxemia and hypoglycemia by lowering Complex I activity and TCA cycle enzyme concentrations, which together, act to lower OCR and NADH production/oxidation in IUGR skeletal muscle.
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Affiliation(s)
- Alexander L Pendleton
- Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona
| | - Andrew T Antolic
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Amy C Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Melissa A Davis
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Leticia E Camacho
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Kevin Doubleday
- Department of Epidemiology and Biostatistics, College of Public Health, University of Arizona, Tucson, Arizona
| | - Miranda J Anderson
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Paul R Langlais
- Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona
- Department of Medicine, University of Arizona, Tucson, Arizona
| | - Ronald M Lynch
- Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona
- Department of Physiology, University of Arizona, Tucson, Arizona
| | - Sean W Limesand
- Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
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Weber C, Hart N, Steyn LV, Papas K, Lynch RM. Characterization of Islet Health and Function Prior to Transplantation. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06703] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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5
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Lynch RM, Aragaki KA, Harnois E, Vagner J, Weber C. Kisspeptin Amplifies GLP‐1 Potentiation of Insulin Secretion by a cAMP Independent Pathway. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06634] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Kelly AC, Smith KE, Purvis WG, Min CG, Weber CS, Cooksey AM, Hasilo C, Paraskevas S, Suszynski TM, Weegman BP, Anderson MJ, Camacho LE, Harland RC, Loudovaris T, Jandova J, Molano DS, Price ND, Georgiev IG, Scott WE, Manas D, Shaw J, O’Gorman D, Kin T, McCarthy FM, Szot GL, Posselt AM, Stock PG, Karatzas T, Shapiro WJ, Lynch RM, Limesand SW, Papas KK. Oxygen Perfusion (Persufflation) of Human Pancreata Enhances Insulin Secretion and Attenuates Islet Proinflammatory Signaling. Transplantation 2019; 103:160-167. [PMID: 30095738 PMCID: PMC6371803 DOI: 10.1097/tp.0000000000002400] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [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: 02/07/2023]
Abstract
BACKGROUND All human islets used in research and for the clinical treatment of diabetes are subject to ischemic damage during pancreas procurement, preservation, and islet isolation. A major factor influencing islet function is exposure of pancreata to cold ischemia during unavoidable windows of preservation by static cold storage (SCS). Improved preservation methods may prevent this functional deterioration. In the present study, we investigated whether pancreas preservation by gaseous oxygen perfusion (persufflation) better preserved islet function versus SCS. METHODS Human pancreata were preserved by SCS or by persufflation in combination with SCS. Islets were subsequently isolated, and preparations in each group matched for SCS or total preservation time were compared using dynamic glucose-stimulated insulin secretion as a measure of β-cell function and RNA sequencing to elucidate transcriptomic changes. RESULTS Persufflated pancreata had reduced SCS time, which resulted in islets with higher glucose-stimulated insulin secretion compared to islets from SCS only pancreata. RNA sequencing of islets from persufflated pancreata identified reduced inflammatory and greater metabolic gene expression, consistent with expectations of reducing cold ischemic exposure. Portions of these transcriptional responses were not associated with time spent in SCS and were attributable to pancreatic reoxygenation. Furthermore, persufflation extended the total preservation time by 50% without any detectable decline in islet function or viability. CONCLUSIONS These data demonstrate that pancreas preservation by persufflation rather than SCS before islet isolation reduces inflammatory responses and promotes metabolic pathways in human islets, which results in improved β cell function.
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Affiliation(s)
- Amy C. Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Kate E. Smith
- Physiological Sciences, University of Arizona, Tucson AZ
| | - William G. Purvis
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | | | - Craig S. Weber
- Physiological Sciences, University of Arizona, Tucson AZ
| | - Amanda M. Cooksey
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Craig Hasilo
- Human Islet Transplant Laboratory, McGill University Health Centre, Montreal, Quebec, CA
| | - Steven Paraskevas
- Human Islet Transplant Laboratory, McGill University Health Centre, Montreal, Quebec, CA
| | - Thomas M. Suszynski
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Bradley P. Weegman
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Miranda J. Anderson
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Leticia E. Camacho
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Robert C. Harland
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Tom Loudovaris
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Jana Jandova
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Diana S. Molano
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Nicholas D. Price
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - Ivan G. Georgiev
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
| | - William E. Scott
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Derek Manas
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - James Shaw
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Doug O’Gorman
- Clinical Islet Transplant Program, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, CA
| | - Tatsuya Kin
- Clinical Islet Transplant Program, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, CA
| | - Fiona M. McCarthy
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Gregory L. Szot
- Department of Surgery, University of California San Francisco, San Francisco, CA
| | - Andrew M. Posselt
- Department of Surgery, University of California San Francisco, San Francisco, CA
| | - Peter G. Stock
- Department of Surgery, University of California San Francisco, San Francisco, CA
| | | | - William J. Shapiro
- Clinical Islet Transplant Program, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, CA
| | | | - Sean W. Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson AZ
| | - Klearchos K. Papas
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson AZ
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7
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Hart NJ, Weber C, Papas KK, Limesand SW, Vagner J, Lynch RM. Multivalent activation of GLP-1 and sulfonylurea receptors modulates β-cell second-messenger signaling and insulin secretion. Am J Physiol Cell Physiol 2018; 316:C48-C56. [PMID: 30404557 DOI: 10.1152/ajpcell.00209.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [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: 12/23/2022]
Abstract
Linking two pharmacophores that bind different cell surface receptors into a single molecule can enhance cell-targeting specificity to cells that express the complementary receptor pair. In this report, we developed and tested a synthetic multivalent ligand consisting of glucagon-like peptide-1 (GLP-1) linked to glibenclamide (Glb) (GLP-1/Glb) for signaling efficacy in β-cells. Expression of receptors for these ligands, as a combination, is relatively specific to the β-cell in the pancreas. The multivalent GLP-1/Glb increased both intracellular cAMP and Ca2+, although Ca2+ responses were significantly depressed compared with the monomeric Glb. Moreover, GLP-1/Glb increased glucose-stimulated insulin secretion in a dose-dependent manner. However, unlike the combined monomers, GLP-1/Glb did not augment insulin secretion at nonstimulatory glucose concentrations in INS 832/13 β-cells or human islets of Langerhans. These data suggest that linking two binding elements, such as GLP-1 and Glb, into a single bivalent ligand can provide a unique functional agent targeted to β-cells.
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Affiliation(s)
| | - Craig Weber
- Department of Physiology, University of Arizona , Tucson, Arizona
| | | | - Sean W Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona , Tucson, Arizona.,BIO5 Institute, University of Arizona , Tucson, Arizona
| | - Josef Vagner
- BIO5 Institute, University of Arizona , Tucson, Arizona
| | - Ronald M Lynch
- Department of Physiology, University of Arizona , Tucson, Arizona.,Department of Pharmacology, University of Arizona , Tucson, Arizona.,BIO5 Institute, University of Arizona , Tucson, Arizona
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8
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Kelly AC, Camacho LE, Pendarvis K, Davenport HM, Steffens NR, Smith KE, Weber CS, Lynch RM, Papas KK, Limesand SW. Adrenergic receptor stimulation suppresses oxidative metabolism in isolated rat islets and Min6 cells. Mol Cell Endocrinol 2018; 473:136-145. [PMID: 29360563 PMCID: PMC6045463 DOI: 10.1016/j.mce.2018.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 01/17/2018] [Accepted: 01/18/2018] [Indexed: 01/24/2023]
Abstract
Insulin secretion is stimulated by glucose metabolism and inhibited by catecholamines through adrenergic receptor stimulation. We determined whether catecholamines suppress oxidative metabolism in β-cells through adrenergic receptors. In Min6 cells and isolated rat islets, epinephrine decreased oxygen consumption rates compared to vehicle control or co-administration of epinephrine with α2-adrenergic receptor antagonist yohimbine. Epinephrine also decreased forskolin-stimulated oxygen consumption rates, indicating cAMP dependent and independent actions. Furthermore, glucose oxidation rates were decreased with epinephrine, independent of the exocytosis of insulin, which was blocked with yohimbine. We evaluated metabolic targets through proteomic analysis after 4 h epinephrine exposure that revealed 466 differentially expressed proteins that were significantly enriched for processes including oxidative metabolism, protein turnover, exocytosis, and cell proliferation. These results demonstrate that acute α2-adrenergic stimulation suppresses glucose oxidation in β-cells independent of nutrient availability and insulin exocytosis, while cAMP concentrations are elevated. Proteomics and immunoblots revealed changes in electron transport chain proteins that were correlated with lower metabolic reducing equivalents, intracellular ATP concentrations, and altered mitochondrial membrane potential implicating a new role for adrenergic control of mitochondrial function and ultimately insulin secretion.
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Affiliation(s)
- Amy C Kelly
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States
| | - Leticia E Camacho
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States
| | - Ken Pendarvis
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States
| | - Hailey M Davenport
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States
| | - Nathan R Steffens
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States
| | - Kate E Smith
- Department of Surgery, University of Arizona, Tucson AZ, United States
| | - Craig S Weber
- Department of Physiology, University of Arizona, Tucson AZ, United States
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson AZ, United States
| | - Klearchos K Papas
- Department of Surgery, University of Arizona, Tucson AZ, United States
| | - Sean W Limesand
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson AZ, United States.
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9
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Smith KE, Purvis WG, Davis MA, Min CG, Cooksey AM, Weber CS, Jandova J, Price ND, Molano DS, Stanton JB, Kelly AC, Steyn LV, Lynch RM, Limesand SW, Alexander M, Lakey JRT, Seeberger K, Korbutt GS, Mueller KR, Hering BJ, McCarthy FM, Papas KK. In vitro characterization of neonatal, juvenile, and adult porcine islet oxygen demand, β-cell function, and transcriptomes. Xenotransplantation 2018; 25:e12432. [PMID: 30052287 DOI: 10.1111/xen.12432] [Citation(s) in RCA: 17] [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] [Received: 01/29/2018] [Revised: 04/20/2018] [Accepted: 05/24/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND There is currently a shortage of human donor pancreata which limits the broad application of islet transplantation as a treatment for type 1 diabetes. Porcine islets have demonstrated potential as an alternative source, but a study evaluating islets from different donor ages under unified protocols has yet to be conducted. METHODS Neonatal porcine islets (NPI; 1-3 days), juvenile porcine islets (JPI; 18-21 days), and adult porcine islets (API; 2+ years) were compared in vitro, including assessments of oxygen consumption rate, membrane integrity determined by FDA/PI staining, β-cell proliferation, dynamic glucose-stimulated insulin secretion, and RNA sequencing. RESULTS Oxygen consumption rate normalized to DNA was not significantly different between ages. Membrane integrity was age dependent, and API had the highest percentage of intact cells. API also had the highest glucose-stimulated insulin secretion response during a dynamic insulin secretion assay and had 50-fold higher total insulin content compared to NPI and JPI. NPI and JPI had similar glucose responsiveness, β-cell percentage, and β-cell proliferation rate. Transcriptome analysis was consistent with physiological assessments. API transcriptomes were enriched for cellular metabolic and insulin secretory pathways, while NPI exhibited higher expression of genes associated with proliferation. CONCLUSIONS The oxygen demand, membrane integrity, β-cell function and proliferation, and transcriptomes of islets from API, JPI, and NPI provide a comprehensive physiological comparison for future studies. These assessments will inform the optimal application of each age of porcine islet to expand the availability of islet transplantation.
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Affiliation(s)
- Kate E Smith
- Department of Physiological Sciences, University of Arizona, Tucson, AZ, USA.,Department of Surgery, University of Arizona, Tucson, AZ, USA
| | | | - Melissa A Davis
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | - Catherine G Min
- Department of Physiological Sciences, University of Arizona, Tucson, AZ, USA.,Department of Surgery, University of Arizona, Tucson, AZ, USA
| | - Amanda M Cooksey
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | - Craig S Weber
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Jana Jandova
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | | | - Diana S Molano
- Department of Surgery, University of Arizona, Tucson, AZ, USA
| | | | - Amy C Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | - Leah V Steyn
- Department of Surgery, University of Arizona, Tucson, AZ, USA
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Sean W Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | - Michael Alexander
- Department of Surgery, University of California-Irvine, Orange, CA, USA
| | | | - Karen Seeberger
- Department of Surgery, Alberta Diabetes Institute, University of Alberta, Edmonton, AL, Canada
| | - Gregory S Korbutt
- Department of Surgery, Alberta Diabetes Institute, University of Alberta, Edmonton, AL, Canada
| | - Kate R Mueller
- Schulze Diabetes Institute, Department of Surgery, University of Minnesota, Minneapolis, MN, USA
| | - Bernhard J Hering
- Schulze Diabetes Institute, Department of Surgery, University of Minnesota, Minneapolis, MN, USA
| | - Fiona M McCarthy
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
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10
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Smith KE, Kelly AC, Min CG, Weber CS, McCarthy FM, Steyn LV, Badarinarayana V, Stanton JB, Kitzmann JP, Strop P, Gruessner AC, Lynch RM, Limesand SW, Papas KK. Acute Ischemia Induced by High-Density Culture Increases Cytokine Expression and Diminishes the Function and Viability of Highly Purified Human Islets of Langerhans. Transplantation 2017; 101:2705-2712. [PMID: 28263224 PMCID: PMC6319561 DOI: 10.1097/tp.0000000000001714] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [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: 09/28/2016] [Revised: 01/24/2017] [Accepted: 02/16/2017] [Indexed: 11/25/2022]
Abstract
BACKGROUND Encapsulation devices have the potential to enable cell-based insulin replacement therapies (such as human islet or stem cell-derived β cell transplantation) without immunosuppression. However, reasonably sized encapsulation devices promote ischemia due to high β cell densities creating prohibitively large diffusional distances for nutrients. It is hypothesized that even acute ischemic exposure will compromise the therapeutic potential of cell-based insulin replacement. In this study, the acute effects of high-density ischemia were investigated in human islets to develop a detailed profile of early ischemia induced changes and targets for intervention. METHODS Human islets were exposed in a pairwise model simulating high-density encapsulation to normoxic or ischemic culture for 12 hours, after which viability and function were measured. RNA sequencing was conducted to assess transcriptome-wide changes in gene expression. RESULTS Islet viability after acute ischemic exposure was reduced compared to normoxic culture conditions (P < 0.01). Insulin secretion was also diminished, with ischemic β cells losing their insulin secretory response to stimulatory glucose levels (P < 0.01). RNA sequencing revealed 657 differentially expressed genes following ischemia, with many that are associated with increased inflammatory and hypoxia-response signaling and decreased nutrient transport and metabolism. CONCLUSIONS In order for cell-based insulin replacement to be applied as a treatment for type 1 diabetes, oxygen and nutrient delivery to β cells will need to be maintained. We demonstrate that even brief ischemic exposure such as would be experienced in encapsulation devices damages islet viability and β cell function and leads to increased inflammatory signaling.
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Affiliation(s)
- Kate E. Smith
- Department of Surgery, University of Arizona, Tucson, AZ
- Department of Physiological Sciences GIDP, University of Arizona, Tucson, AZ
| | - Amy C. Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ
| | - Catherine G. Min
- Department of Surgery, University of Arizona, Tucson, AZ
- Department of Physiological Sciences GIDP, University of Arizona, Tucson, AZ
| | - Craig S. Weber
- Department of Physiology, University of Arizona, Tucson, AZ
| | - Fiona M. McCarthy
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ
| | - Leah V. Steyn
- Department of Surgery, University of Arizona, Tucson, AZ
| | | | | | | | - Peter Strop
- Sanofi-Aventis Group, Tucson, AZ
- Icagen, Inc., Tucson, AZ
| | | | | | - Sean W. Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ
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11
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McKay BS, Lynch RM, Stamer WD. Comment on "Identification of Novel G Protein-Coupled Receptor 143 Ligands as Pharmacologic Tools for Investigating X-Linked Ocular Albinism". Invest Ophthalmol Vis Sci 2017; 58:4733-4734. [PMID: 28910826 PMCID: PMC5600132 DOI: 10.1167/iovs.17-22660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Brian S McKay
- Department of Ophthalmology and Vision Science, University of Arizona, Tucson, Arizona, United States
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson, Arizona, United States
| | - W Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, North Carolina, United States; and the.,Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States
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12
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Chen X, Kelly AC, Yates DT, Macko AR, Lynch RM, Limesand SW. Islet adaptations in fetal sheep persist following chronic exposure to high norepinephrine. J Endocrinol 2017; 232:285-295. [PMID: 27888197 PMCID: PMC5173394 DOI: 10.1530/joe-16-0445] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 11/25/2016] [Indexed: 11/08/2022]
Abstract
Complications in pregnancy elevate fetal norepinephrine (NE) concentrations. Previous studies in NE-infused sheep fetuses revealed that sustained exposure to high NE resulted in lower expression of α2-adrenergic receptors in islets and increased insulin secretion responsiveness after acutely terminating the NE infusion. In this study, we determined if the compensatory increase in insulin secretion after chronic elevation of NE is independent of hyperglycemia in sheep fetuses and whether it is persistent in conjunction with islet desensitization to NE. After an initial assessment of glucose-stimulated insulin secretion (GSIS) at 129 ± 1 days of gestation, fetuses were continuously infused for seven days with NE and maintained at euglycemia with a maternal insulin infusion. Fetal GSIS studies were performed again on days 8 and 12. Adrenergic sensitivity was determined in pancreatic islets collected at day 12. NE infusion increased (P < 0.01) fetal plasma NE concentrations and lowered (P < 0.01) basal insulin concentrations compared to vehicle-infused controls. GSIS was 1.8-fold greater (P < 0.05) in NE-infused fetuses compared to controls at both one and five days after discontinuing the infusion. Glucose-potentiated arginine-induced insulin secretion was also enhanced (P < 0.01) in NE-infused fetuses. Maximum GSIS in islets isolated from NE-infused fetuses was 1.6-fold greater (P < 0.05) than controls, but islet insulin content and intracellular calcium signaling were not different between treatments. The half-maximal inhibitory concentration for NE was 2.6-fold greater (P < 0.05) in NE-infused islets compared to controls. These findings show that chronic NE exposure and not hyperglycemia produce persistent adaptations in pancreatic islets that augment β-cell responsiveness in part through decreased adrenergic sensitivity.
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Affiliation(s)
- Xiaochuan Chen
- Chongqing Key Laboratory of Forage & HerbivoreCollege of Animal Science and Technology, Southwest University, Chongqing, China
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Amy C Kelly
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Dustin T Yates
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Antoni R Macko
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
| | - Ronald M Lynch
- Department of PhysiologyUniversity of Arizona, Tucson, Arizona, USA
| | - Sean W Limesand
- School of Animal and Comparative Biomedical SciencesUniversity of Arizona, Tucson, Arizona, USA
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13
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Dehigaspitiya DC, Anglin BL, Smith KR, Weber CS, Lynch RM, Mash EA. Linear scaffolds for multivalent targeting of melanocortin receptors. Org Biomol Chem 2015; 13:11507-17. [PMID: 26461460 DOI: 10.1039/c5ob01779c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecules bearing one, two, three, or four copies of the tetrapeptide His-dPhe-Arg-Trp were attached to scaffolds based on ethylene glycol, glycerol, and d-mannitol by means of the copper-assisted azide-alkyne cyclization. The abilities of these compounds to block binding of a probe at the melanocortin 4 receptor were evaluated using a competitive binding assay. All of the multivalent molecules studied exhibited 30- to 40-fold higher apparent affinites when compared to a monovalent control. These results are consistent with divalent binding to receptor dimers. No evidence for tri- or tetravalent binding was obtained. Differences in the interligand spacing required for divalent binding, as opposed to tri- or tetravalent binding, may be responsible for these results.
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14
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Ledgerwood JE, Coates EE, Yamshchikov G, Saunders JG, Holman L, Enama ME, DeZure A, Lynch RM, Gordon I, Plummer S, Hendel CS, Pegu A, Conan-Cibotti M, Sitar S, Bailer RT, Narpala S, McDermott A, Louder M, O'Dell S, Mohan S, Pandey JP, Schwartz RM, Hu Z, Koup RA, Capparelli E, Mascola JR, Graham BS. Safety, pharmacokinetics and neutralization of the broadly neutralizing HIV-1 human monoclonal antibody VRC01 in healthy adults. Clin Exp Immunol 2015; 182:289-301. [PMID: 26332605 DOI: 10.1111/cei.12692] [Citation(s) in RCA: 202] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2015] [Indexed: 12/17/2022] Open
Abstract
VRC-HIVMAB060-00-AB (VRC01) is a broadly neutralizing HIV-1 monoclonal antibody (mAb) isolated from the B cells of an HIV-infected patient. It is directed against the HIV-1 CD4 binding site and is capable of potently neutralizing the majority of diverse HIV-1 strains. This Phase I dose-escalation study in healthy adults was conducted at the National Institutes of Health (NIH) Clinical Center (Bethesda, MD, USA). Primary objectives were the safety, tolerability and pharmacokinetics (PK) of VRC01 intravenous (i.v.) infusion at 5, 20 or 40 mg/kg, given either once (20 mg/kg) or twice 28 days apart (all doses), and of subcutaneous (s.c.) delivery at 5 mg/kg compared to s.c. placebo given twice, 28 days apart. Cumulatively, 28 subjects received 43 VRC01 and nine received placebo administrations. There were no serious adverse events or dose-limiting toxicities. Mean 28-day serum trough concentrations after the first infusion were 35 and 57 μg/ml for groups infused with 20 mg/kg (n = 8) and 40 mg/kg (n = 5) doses, respectively. Mean 28-day trough concentrations after the second infusion were 56 and 89 μg/ml for the same two doses. Over the 5-40 mg/kg i.v. dose range (n = 18), the clearance was 0.016 l/h and terminal half-life was 15 days. After infusion VRC01 retained expected neutralizing activity in serum, and anti-VRC01 antibody responses were not detected. The human monoclonal antibody (mAb) VRC01 was well tolerated when delivered i.v. or s.c. The mAb demonstrated expected half-life and pharmacokinetics for a human immunoglobulin G. The safety and PK results support and inform VRC01 dosing schedules for planning HIV-1 prevention efficacy studies.
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Affiliation(s)
- J E Ledgerwood
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - E E Coates
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - G Yamshchikov
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - J G Saunders
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - L Holman
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - M E Enama
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - A DeZure
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - R M Lynch
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - I Gordon
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - S Plummer
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - C S Hendel
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - A Pegu
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - M Conan-Cibotti
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - S Sitar
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - R T Bailer
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - S Narpala
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - A McDermott
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - M Louder
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - S O'Dell
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - S Mohan
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, USA
| | - J P Pandey
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, USA
| | - R M Schwartz
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Z Hu
- Biostatistics Research Branch, Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - R A Koup
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - E Capparelli
- School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
| | - J R Mascola
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - B S Graham
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
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Elshan NGRD, Jayasundera T, Anglin BL, Weber CS, Lynch RM, Mash EA. Trigonal scaffolds for multivalent targeting of melanocortin receptors. Org Biomol Chem 2015; 13:1778-91. [PMID: 25502141 DOI: 10.1039/c4ob02094d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Melanocortin receptors can be used as biomarkers to detect and possibly treat melanoma. To these ends, molecules bearing one, two, or three copies of the weakly binding ligand MSH(4) were attached to scaffolds based on phloroglucinol, tripropargylamine, and 1,4,7-triazacyclononane by means of the copper-assisted azide-alkyne cyclization. This synthetic design allows rapid assembly of multivalent molecules. The bioactivities of these compounds were evaluated using a competitive binding assay that employed human embryonic kidney cells engineered to overexpress the melanocortin 4 receptor. The divalent molecules exhibited 10- to 30-fold higher levels of inhibition when compared to the corresponding monovalent molecules, consistent with divalent binding. The trivalent molecules were only statistically (∼2-fold) better than the divalent molecules, still consistent with divalent binding but inconsistent with trivalent binding. Possible reasons for these behaviors and planned refinements of the multivalent constructs targeting melanocortin receptors based on these scaffolds are discussed.
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Affiliation(s)
- N G R Dayan Elshan
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721-0041, USA.
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16
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Abstract
Oligomers incorporating the tetrapeptide MSH4, the minimum active sequence of melanocyte stimulating hormone, were synthesized by an A2 + B2 strategy involving microwave-assisted copper-catalyzed azide-alkyne cycloaddition. A2 contained an MSH4 core while B2 contained a (Pro-Gly)3 spacer. Soluble mixtures containing compounds with up to eight MSH4 units were obtained from oligomerizations at high monomer concentrations. The avidities of several oligomeric mixtures were evaluated by means of a competitive binding assay using HEK293 cells engineered to overexpress the melanocortin 4 receptor. When based on total MSH4 concentrations, avidities were only minimally enhanced compared with a monovalent control. The lack of variation in the effect of ligands on probe binding is consistent with high off rates for MSH4 in both monovalent and oligomeric constructs relative to that of the competing probe.
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Affiliation(s)
| | - Suryakiran Navath
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041, USA
| | - Craig S. Weber
- Department of Physiology, University of Arizona, Tucson, AZ 85724-5051, USA
| | - Ronald M. Lynch
- Department of Physiology, University of Arizona, Tucson, AZ 85724-5051, USA
- The Bio5 Institute, University of Arizona, Tucson, AZ 85721-0240, USA
| | - Eugene A. Mash
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041, USA
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17
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Elshan NGRD, Jayasundera T, Weber CS, Lynch RM, Mash EA. Development of a time-resolved fluorescence probe for evaluation of competitive binding to the cholecystokinin 2 receptor. Bioorg Med Chem 2015; 23:1841-8. [PMID: 25769518 PMCID: PMC4380538 DOI: 10.1016/j.bmc.2015.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/06/2015] [Accepted: 02/16/2015] [Indexed: 10/23/2022]
Abstract
The synthesis, characterization, and use of Eu-DTPA-PEGO-Trp-Nle-Asp-Phe-NH2 (Eu-DTPA-PEGO-CCK4), a luminescent probe targeted to cholecystokinin 2 receptor (CCK2R, aka CCKBR), are described. The probe was prepared by solid phase synthesis. A Kd value of 17±2nM was determined by means of saturation binding assays using HEK-293 cells that overexpress CCK2R. The probe was then used in competitive binding assays against Ac-CCK4 and three new trivalent CCK4 compounds. Repeatable and reproducible binding assay results were obtained. Given its ease of synthesis, purification, receptor binding properties, and utility in competitive binding assays, Eu-DTPA-PEGO-CCK4 could become a standard tool for high-throughput screening of compounds in development targeted to cholecystokinin receptors.
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Affiliation(s)
- N G R Dayan Elshan
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041, USA
| | | | - Craig S Weber
- Department of Physiology, University of Arizona, Tucson, AZ 85724-5051, USA
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson, AZ 85724-5051, USA; The Bio5 Institute, University of Arizona, Tucson, AZ 85721-0240, USA
| | - Eugene A Mash
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041, USA.
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18
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Marmorstein AD, Kinnick TR, Stanton JB, Johnson AA, Lynch RM, Marmorstein LY. Bestrophin-1 influences transepithelial electrical properties and Ca2+ signaling in human retinal pigment epithelium. Mol Vis 2015; 21:347-59. [PMID: 25878489 PMCID: PMC4390793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/30/2015] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Mutations in BEST1, encoding Bestrophin-1 (Best1), cause Best vitelliform macular dystrophy (BVMD) and other inherited retinal degenerative diseases. Best1 is an integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium (RPE). Data from numerous in vitro and in vivo models have demonstrated that Best1 regulates intracellular Ca2+ levels. Although it is known from in vitro and crystal structure data that Best1 is also a calcium-activated anion channel, evidence for Best1 functioning as a channel in human RPE is lacking. To assess Best1-associated channel activity in the RPE, we examined the transepithelial electrical properties of fetal human RPE (fhRPE) cells, which express endogenous Best1. METHODS Using adenovirus-mediated gene transfer, we overexpressed Best1 and the BVMD mutant Best1W93C in fhRPE cells and assessed resting transepithelial potential (TEP), transepithelial resistance, short circuit current (Isc), and intracellular Ca2+ levels. Cl- currents were directly measured in transfected HEK293 cells using whole-cell patch clamp. RESULTS Best1W93C showed ablated Cl- currents and, when co-expressed, suppressed the channel activity of Best1 in HEK293 cells. In fhRPE, overexpression of Best1 increased TEP and Isc, while Best1W93C diminished TEP and Isc. Substitution of Cl- in the bath media resulted in a significant reduction of Isc in monolayers overexpressing Best1, but no significant Isc change in monolayers expressing Best1W93C. We removed Ca2+ as a limit on transepithelial electrical properties by treating cells with ionomycin, and found that changes in Isc and TEP for monolayers expressing Best1 were absent in monolayers expressing Best1W93C. Similarly, inhibition of calcium-activated anion channels with niflumic acid reduced both Isc and TEP of control and Best1 monolayers, but did not notably affect Best1W93C monolayers. Stimulation with extracellular ATP induced an increase in TEP in control monolayers that was greater than that observed in those expressing Best1(W93C). Examination of [Ca2+]i following ATP stimulation demonstrated that the expression of Best1W93C impaired intracellular Ca2+ signaling. CONCLUSIONS These data indicate that Best1 activity strongly influences electrophysiology and Ca2+ signaling in RPE cells, and that a common BVMD mutation disrupts both of these parameters. Our findings support the hypothesis that Best1 functions as an anion channel in human RPE.
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19
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Steyn LV, Ananthakrishnan K, Anderson MJ, Patek R, Kelly A, Vagner J, Lynch RM, Limesand SW. A Synthetic Heterobivalent Ligand Composed of Glucagon-Like Peptide 1 and Yohimbine Specifically Targets β Cells Within the Pancreas. Mol Imaging Biol 2015; 17:461-70. [PMID: 25604385 DOI: 10.1007/s11307-014-0817-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 12/11/2014] [Accepted: 12/18/2014] [Indexed: 12/15/2022]
Abstract
PURPOSE β Cell specificity for a heterobivalent ligand composed of glucagon-like peptide-1 (GLP-1) linked to yohimbine (GLP-1/Yhb) was evaluated to determine its utility as a noninvasive imaging agent. PROCEDURES Competition binding assays were performed on βTC3 cells and isolated rat islets. Immunostaining for insulin was used to co-localized intravenously injected Cy5-labeled GLP-1/Yhb in β cells of Sprague-Dawley rats. Rats were intravenously injected with In-111-labeled GLP-1/Yhb to determine clearance rates and tissue biodistribution. Tissue-specific binding was confirmed by competition with pre-administration of unlabeled GLP-1/Yhb and in Streptozotocin-induced diabetic rats. RESULTS In βTC3 cells, high affinity binding of GLP-1/Yhb required interactions with both receptors because monovalent competition or receptor knockdown with RNAi lowered specificity and avidity of the heterobivalent ligand. Binding specificity for isolated islets was 2.6-fold greater than that of acinar tissue or islets pre-incubated with excess unlabeled GLP-1/Yhb. Immunofluorescent localization of Cy5-labeled GLP-1/Yhb was restricted to pancreatic islets. Within 30 min, ~90% of the In-111-labeled GLP-1/Yhb was cleared from blood. Tissue-specific accumulation of radiolabeled ligand was apparent in the pancreas, but not in other tissues within the abdominal imaging field. Pancreas specificity was lost in Streptozotocin-induced diabetic rats. CONCLUSIONS The GLP-1/Yhb exhibits high specificity for β cells, rapid blood clearance rates, and low non-specific uptake by other tissues within the abdominal imaging field. These characteristics of GLP-1/Yhb are desirable for application to β cell imaging in vivo and provide a basis for developing additional multivalent β cell-specific targeting agents to aid in the management of type 1 diabetes.
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Affiliation(s)
- Leah V Steyn
- School of Animal and Comparative Biomedical Sciences, William J. Parker Agricultural Research Center, The University of Arizona, 4101 N Campbell Ave, Tucson, AZ, 85719, USA
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20
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Kelly AC, Steyn LV, Kitzmann JP, Anderson MJ, Mueller KR, Hart NJ, Lynch RM, Papas KK, Limesand SW. Function and expression of sulfonylurea, adrenergic, and glucagon-like peptide 1 receptors in isolated porcine islets. Xenotransplantation 2014; 21:385-91. [PMID: 24801676 DOI: 10.1111/xen.12101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [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: 12/06/2013] [Accepted: 03/14/2014] [Indexed: 11/29/2022]
Abstract
The scarcity of human cadaveric pancreata limits large-scale application of islet transplantation for patients with diabetes. Islets isolated from pathogen-free pigs provide an economical and abundant alternative source assuming immunologic barriers are appropriate. Membrane receptors involved in insulin secretion that also have potential as imaging targets were investigated in isolated porcine islets. Quantitative (q)PCR revealed that porcine islets express mRNA transcripts for sulfonylurea receptor 1 (Sur1), inward rectifying potassium channel (Kir6.2, associated with Sur1), glucagon-like peptide 1 receptor (GLP1R), and adrenergic receptor alpha 2A (ADRα2A). Receptor function was assessed in static incubations with stimulatory glucose concentrations, and in the presence of receptor agonists. Glibenclamide, an anti-diabetic sulfonylurea, and exendin-4, a GLP-1 mimetic, potentiated glucose-stimulated insulin secretion >2-fold. Conversely, epinephrine maximally reduced insulin secretion 72 ± 9% (P < 0.05) and had a half maximal inhibitory concentration of 60 nm in porcine islets (95% confidence interval of 45-830 nm). The epinephrine action was inhibited by the ADRα2A antagonist yohimbine. Our findings demonstrate that porcine islets express and are responsive to both stimulatory and inhibitory membrane localized receptors, which can be used as imaging targets after transplantation or to modify insulin secretion.
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Affiliation(s)
- Amy C Kelly
- School of Comparative Animal and Biomedical Sciences, University of Arizona, Tucson, AZ, USA
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21
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Hart NJ, Chung WJ, Weber C, Ananthakrishnan K, Anderson M, Patek R, Zhang Z, Limesand SW, Vagner J, Lynch RM. Hetero-bivalent GLP-1/glibenclamide for targeting pancreatic β-cells. Chembiochem 2013; 15:135-45. [PMID: 24259278 DOI: 10.1002/cbic.201300375] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [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: 06/10/2013] [Indexed: 01/15/2023]
Abstract
G protein-coupled receptor (GPCR) cell signalling cascades are initiated upon binding of a specific agonist ligand to its cell surface receptor. Linking multiple heterologous ligands that simultaneously bind and potentially link different receptors on the cell surface is a unique approach to modulate cell responses. Moreover, if the target receptors are selected based on analysis of cell-specific expression of a receptor combination, then the linked binding elements might provide enhanced specificity of targeting the cell type of interest, that is, only to cells that express the complementary receptors. Two receptors whose expression is relatively specific (in combination) to insulin-secreting pancreatic β-cells are the sulfonylurea-1 (SUR1) and the glucagon-like peptide-1 (GLP-1) receptors. A heterobivalent ligand was assembled from the active fragment of GLP-1 (7-36 GLP-1) and glibenclamide, a small organic ligand for SUR1. The synthetic construct was labelled with Cy5 or europium chelated in DTPA to evaluate binding to β-cells, by using fluorescence microscopy or time-resolved saturation and competition binding assays, respectively. Once the ligand binds to β-cells, it is rapidly capped and presumably removed from the cell surface by endocytosis. The bivalent ligand had an affinity approximately fivefold higher than monomeric europium-labelled GLP-1, likely a result of cooperative binding to the complementary receptors on the βTC3 cells. The high-affinity binding was lost in the presence of either unlabelled monomer, thus demonstrating that interaction with both receptors is required for the enhanced binding at low concentrations. Importantly, bivalent enhancement was accomplished in a cell system with physiological levels of expression of the complementary receptors, thus indicating that this approach might be applicable for β-cell targeting in vivo.
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Affiliation(s)
- Nathaniel J Hart
- Department of Physiological Sciences, University of Arizona, 1656 E. Mabel St., Tucson, AZ 85721 (USA)
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22
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Alleti R, Vagner J, Dehigaspitiya DC, Moberg VE, Elshan NGRD, Tafreshi NK, Brabez N, Weber CS, Lynch RM, Hruby VJ, Gillies RJ, Morse DL, Mash EA. Synthesis and characterization of time-resolved fluorescence probes for evaluation of competitive binding to melanocortin receptors. Bioorg Med Chem 2013; 21:5029-38. [PMID: 23890524 DOI: 10.1016/j.bmc.2013.06.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [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: 04/30/2013] [Revised: 06/14/2013] [Accepted: 06/22/2013] [Indexed: 11/28/2022]
Abstract
Probes for use in time-resolved fluorescence competitive binding assays at melanocortin receptors based on the parental ligands MSH(4), MSH(7), and NDP-α-MSH were prepared by solid phase synthesis methods, purified, and characterized. The saturation binding of these probes was studied using HEK-293 cells engineered to overexpress the human melanocortin 4 receptor (hMC4R) as well as the human cholecystokinin 2 receptor (hCCK2R). The ratios of non-specific binding to total binding approached unity at high concentrations for each probe. At low probe concentrations, receptor-mediated binding and uptake was discernable, and so probe concentrations were kept as low as possible in determining Kd values. The Eu-DTPA-PEGO-MSH(4) probe exhibited low specific binding relative to non-specific binding, even at low nanomolar concentrations, and was deemed unsuitable for use in competition binding assays. The Eu-DTPA-PEGO probes based on MSH(7) and NDP-α-MSH exhibited Kd values of 27±3.9nM and 4.2±0.48nM, respectively, for binding with hMC4R. These probes were employed in competitive binding assays to characterize the interactions of hMC4R with monovalent and divalent MSH(4), MSH(7), and NDP-α-MSH constructs derived from squalene. Results from assays with both probes reflected only statistical enhancements, suggesting improper ligand spacing on the squalene scaffold for the divalent constructs. The Ki values from competitive binding assays that employed the MSH(7)-based probe were generally lower than the Ki values obtained when the probe based on NDP-α-MSH was employed, which is consistent with the greater potency of the latter probe. The probe based on MSH(7) was also competed with monovalent, divalent, and trivalent MSH(4) constructs that previously demonstrated multivalent binding in competitive binding assays against a variant of the probe based on NDP-α-MSH. Results from these assays confirm multivalent binding, but suggest a more modest increase in avidity for these MSH(4) constructs than was previously reported.
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Key Words
- 1-(9H-fluoren-9-yl)-3,19-dioxo-2,8,11,14,21-pentaoxa-4,18-diazatricosan-23-oic acid
- 1-hydroxybenzotriazole
- 19-amino-5-oxo-3,10,13,16-tetraoxa-6-azanonadecan-1-oic acid
- 6-chloro-1-hydroxybenzotriazole
- 9-fluorenylmethyoxycarbonyl
- Ac-Ser-Tyr-Ser-Nle-Glu-His-DPhe-Arg-Trp-Gly-Lys-Pro-Val-NH(2)
- BSA
- Cl-HOBt
- Competition binding assays
- CuAAC
- DCM
- DIC
- DIEA
- DMEM
- DMF
- DMSO
- DTPA
- Dulbecco’s Modified Eagle Medium
- ESI MS
- FT-ICR MS
- Fluorescent probes
- Fmoc
- Fmoc-PEGO
- Fourier transform ion cyclotron resonance mass spectrometry
- HOBt
- HRMS
- His-DPhe-Arg-Trp
- IC(50)
- MEM
- MSH(4)
- MSH(7)
- Melanocortin 4 receptor
- Minimum Essential Medium
- N,N-dimethylformamide
- NDP-α-MSH
- PEGO
- Saturation binding assays
- Ser-Nle-Glu-His-DPhe-Arg-Trp
- TBTA
- TEAA
- TFA
- THF
- TLC
- TRF
- Time-resolved fluorescence
- bovine serum albumin
- copper(I)-catalyzed azide-alkyne cycloaddition
- dichloromethane
- diethylenetriaminepentaacetic acid
- diisopropyl carbodiimide
- diisopropylethylamine
- dimethyl sulfoxide
- electrospray ionization mass spectrometry
- hMC4R
- half maximal inhibitory concentration
- high resolution mass spectroscopy
- human melanocortin 4 receptor
- tetrahydrofuran
- thin-layer chromatography
- time-resolved fluorescence
- triethylammonium acetate
- trifluoroacetic acid
- tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine
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Affiliation(s)
- Ramesh Alleti
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721-0041, USA
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Escalante AM, McGrath RT, Karolak MR, Dorr RT, Lynch RM, Landowski TH. Preventing the autophagic survival response by inhibition of calpain enhances the cytotoxic activity of bortezomib in vitro and in vivo. Cancer Chemother Pharmacol 2013; 71:1567-76. [PMID: 23572175 PMCID: PMC3669633 DOI: 10.1007/s00280-013-2156-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/21/2013] [Indexed: 02/07/2023]
Abstract
PURPOSE Bortezomib, a first-generation proteasome inhibitor, induces an endoplasmic reticulum (ER) stress response, which ultimately leads to dysregulation of intracellular Ca(2+) and apoptotic cell death. This study investigated the role of the Ca(2+)-dependent enzyme, calpain, in bortezomib cytotoxicity. A novel therapeutic combination was evaluated in which HIV protease inhibitors were used to block calpain activity and enhance bortezomib cytotoxicity in myeloma cells in vitro and in vivo. METHODS Bortezomib-mediated cell death was examined using assays for apoptosis (Annexin V staining), total cell death (trypan blue exclusion), and growth inhibition (MTT). The effects of calpain on bortezomib-induced cytotoxicity were investigated using siRNA knockdown or pharmaceutical inhibitors. Enzyme activity assays and immunofluorescence analysis were used to identify mechanistic effects. RESULTS Inhibition of the Ca(2+)-dependent cysteine protease calpain, either by pharmacologic or genetic means, enhances or accelerates bortezomib-induced myeloma cell death. The increase in cell death is not associated with an increase in caspase activity, nor is there evidence of greater inhibition of proteasome activity, suggesting an alternate, calpain-regulated mechanism of bortezomib-induced cell death. Bortezomib initiates an autophagic response in myeloma cells associated with cell survival. Inhibition of calpain subverts the cytoprotective function of autophagy leading to increased bortezomib-mediated cell death. Combination therapy with bortezomib and the calpain-blocking HIV protease inhibitor, nelfinavir, reversed bortezomib resistance and induced near-complete tumor regressions in an SCID mouse xenograft model of myeloma.
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Affiliation(s)
- Aluvia M Escalante
- Department of Medicine, University of Arizona Cancer Center, University of Arizona, 1515 North Campbell Avenue, Room 4963B, Tucson, AZ 85724, USA
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24
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Sarkar DD, Edwards SK, Mauser JA, Suarez AM, Serowoky MA, Hudok NL, Hudok PL, Nuñez M, Weber CS, Lynch RM, Miyashita O, Tsao TS. Increased redox-sensitive green fluorescent protein reduction potential in the endoplasmic reticulum following glutathione-mediated dimerization. Biochemistry 2013; 52:3332-45. [PMID: 23594148 DOI: 10.1021/bi400052u] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
As the endoplasmic reticulum (ER) is the compartment where disulfide bridges in secreted and cell surface proteins are formed, the disturbance of its redox state has profound consequences, yet regulation of ER redox potential remains poorly understood. To monitor the ER redox state in live cells, several fluorescence-based sensors have been developed. However, these sensors have yielded results that are inconsistent with each other and with earlier non-fluorescence-based studies. One particular green fluorescent protein (GFP)-based redox sensor, roGFP1-iL, could detect oxidizing changes in the ER despite having a reduction potential significantly lower than that previously reported for the ER. We have confirmed these observations and determined the mechanisms by which roGFP1-iL detects oxidizing changes. First, glutathione mediates the formation of disulfide-bonded roGFP1-iL dimers with an intermediate excitation fluorescence spectrum resembling a mixture of oxidized and reduced monomers. Second, glutathione facilitates dimerization of roGFP1-iL, which shifted the equilibrium from oxidized monomers to dimers, thereby increasing the molecule's reduction potential compared with that of a dithiol redox buffer. We conclude that the glutathione redox couple in the ER significantly increased the reduction potential of roGFP1-iL in vivo by facilitating its dimerization while preserving its ratiometric nature, which makes it suitable for monitoring oxidizing and reducing changes in the ER with a high degree of reliability in real time. The ability of roGFP1-iL to detect both oxidizing and reducing changes in ER and its dynamic response in glutathione redox buffer between approximately -190 and -130 mV in vitro suggests a range of ER redox potentials consistent with those determined by earlier approaches that did not involve fluorescent sensors.
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Affiliation(s)
- Deboleena Dipak Sarkar
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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25
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Richardson VA, Weber CS, Lynch RM, Dokken BB. Glucagon‐like Peptide‐1 (GLP‐1) Attenuates Agoniststimulated Cytosolic Free Calcium ([Ca2+]i) Signaling and the Production of F2α‐isoprostane in Endothelial Cells. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.900.5] [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: 11/11/2022]
Affiliation(s)
- Vanitra A Richardson
- MedicineUniversity of ArizonaTucsonAZ
- Physiological Sciences GIDPUniversity of ArizonaTucsonAZ
| | | | - Ronald M Lynch
- Physiological Sciences GIDPUniversity of ArizonaTucsonAZ
- PhysiologyUniversity of ArizonaTucsonAZ
| | - Betsy B Dokken
- MedicineUniversity of ArizonaTucsonAZ
- Physiological Sciences GIDPUniversity of ArizonaTucsonAZ
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26
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Ananthakrishnan K, Penrod LV, Hart NJ, Weber CS, Anderson M, Vagner J, Limesand SW, Lynch RM. Multivalent GLP‐1/Yhb for targeted therapy and imaging of pancreatic β‐cells. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1154.18] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | | | | | | | - Ronald M. Lynch
- Physiological SciencesUniversity of ArizonaTucsonAZ
- BIO5 InstituteUniversity of ArizonaTucsonAZ
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27
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Abstract
Although changes in both pH(in) and [Ca(2+)](i) have been observed in response to a variety of agonists, it is not clear whether these ionic events work independently or are coordinated to lead to a specific physiological response. One of the fundamental problems in studying these ionic events is that changes in pH(in) modify Ca(2+) regulatory mechanisms and changes in Ca(2+) may modify pH regulation. It is desirable to use a technique that allows concomitant monitoring of these two ions in cell populations with high time resolution. Furthermore, like many Ca(2+) binding proteins, all Ca(2+)-sensitive fluoroprobes are inherently sensitive to pH owing to competition of H(+) for the Ca(2+)-binding sites. This chapter describes experimental paradigms that provide optimum conditions for simultaneous measurement of pH from the fluorescence emission of snarf-1, and Ca(2+) using fura-2. The fluorescence spectra of these compounds are sufficiently different to allow simultaneous measurement of pH and Ca(2+) both in vitro and in vivo. Moreover, the ratio of the H(+)-sensitive wavelengths of snarf-1 is unaffected by Ca(2+), or the concomitant presence of fura-2 in cells. Although the fluorescence ratio of fura-2 is insensitive to the presence of snarf-1, it is affected by pH, as indicated above. We describe procedures to correct for this effect and to obtain calibration parameters for fura-2 and snarf-1 required to facilitate analysis of pH and Ca(2+) concentrations within cell populations.
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Affiliation(s)
- Raul Martinez-Zaguilan
- Department of Physiology, Texas Tech University Health Sciences Center, Lubbock, TX, USA
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28
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Brabez N, Saunders K, Nguyen KL, Jayasundera T, Weber C, Lynch RM, Chassaing G, Lavielle S, Hruby VJ. Multivalent Interactions: Synthesis and Evaluation of Melanotropin Multimers - Tools for Melanoma Targeting. ACS Med Chem Lett 2013; 4:98-102. [PMID: 23524643 DOI: 10.1021/ml300312b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [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: 11/30/2022] Open
Abstract
In order to develop agents for early detection and selective treatment of melanomas, high affinity and high specificity molecular tools are required. Enhanced specificity may be obtained by simultaneously binding to multiple cell surface targets via the use of multimeric analogs of naturally occurring ligands. Trimers targeting overexpressed melanocortin receptors have been found to be potential candidates for this purpose. In the present letter, we describe the synthesis and study of multimers based on a dendrimer-like scaffold. The binding affinity and activity results revealed that dendrimers promote multivalent interactions via statistical and/or cooperative effects on binding. Moreover, viability studies showed no significant toxicity at micromolar concentrations, which will allow these molecular complexes to be used in vivo. Finally, imaging studies showed effective internalization for all the molecules confirming their potential as delivery agents.
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Affiliation(s)
- Nabila Brabez
- UPMC Paris 06, UMR 7203, Laboratoire des BioMolécules, Université P. et M. Curie, 75005 Paris, France
- CNRS, UMR 7203, France
- ENS,
UMR 7203, Département de Chimie, Ecole Normale Supérieure, 75005 Paris, France
| | | | | | | | | | | | - Gerard Chassaing
- UPMC Paris 06, UMR 7203, Laboratoire des BioMolécules, Université P. et M. Curie, 75005 Paris, France
- CNRS, UMR 7203, France
- ENS,
UMR 7203, Département de Chimie, Ecole Normale Supérieure, 75005 Paris, France
| | - Solange Lavielle
- UPMC Paris 06, UMR 7203, Laboratoire des BioMolécules, Université P. et M. Curie, 75005 Paris, France
- CNRS, UMR 7203, France
- ENS,
UMR 7203, Département de Chimie, Ecole Normale Supérieure, 75005 Paris, France
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29
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Konhilas JP, Behunin SM, Lynch RM. Keeping the beat. Focus on “Enrichment of neonatal rat cardiomyocytes in primary culture facilitates long-term maintenance of contractility in vitro”. Am J Physiol Cell Physiol 2012; 303:C1218-9. [DOI: 10.1152/ajpcell.00310.2012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- John P. Konhilas
- Department of Physiology, the BIO5 Institute, and the Sarver Molecular Cardiovascular Program, University of Arizona, College of Medicine, Tucson, Arizona
| | - Samantha M. Behunin
- Department of Physiology, the BIO5 Institute, and the Sarver Molecular Cardiovascular Program, University of Arizona, College of Medicine, Tucson, Arizona
| | - Ronald M. Lynch
- Department of Physiology, the BIO5 Institute, and the Sarver Molecular Cardiovascular Program, University of Arizona, College of Medicine, Tucson, Arizona
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30
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Lynch RM, Tran L, Wu X, Li Y, Lee B, Mascola J. Characterizing the fitness cost of viral escape from the HIV-1 broadly neutralizing monoclonal antibody VRC01. Retrovirology 2012. [PMCID: PMC3442067 DOI: 10.1186/1742-4690-9-s2-p87] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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31
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Green AS, Chen X, Macko AR, Anderson MJ, Kelly AC, Hart NJ, Lynch RM, Limesand SW. Chronic pulsatile hyperglycemia reduces insulin secretion and increases accumulation of reactive oxygen species in fetal sheep islets. J Endocrinol 2012; 212:327-42. [PMID: 22182602 PMCID: PMC3516619 DOI: 10.1530/joe-11-0300] [Citation(s) in RCA: 12] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Children from diabetic pregnancies have a greater incidence of type 2 diabetes. Our objective was to determine if exposure to mild-moderate hyperglycemia, by modeling managed diabetic pregnancies, affects fetal β-cell function. In sheep fetuses, β-cell responsiveness was examined after 2 weeks of sustained hyperglycemia with 3 pulses/day, mimicking postprandial excursions, and compared to saline-infused controls (n = 10). Two pulsatile hyperglycemia (PHG) treatments were studied: mild (mPHG, n = 5) with +15% sustained and +55% pulse; and moderate (PHG, n = 10) with +20% sustained and +100% pulse. Fetal glucose-stimulated insulin secretion and glucose-potentiated arginine insulin secretion were lower (P < 0.05) in PHG (0.86 ± 0.13 and 2.91 ± 0.39 ng/ml plasma insulin) but not in mPHG fetuses (1.21 ± 0.08 and 4.25 ± 0.56 ng/ml) compared to controls (1.58 ± 0.25 and 4.51 ± 0.56 ng/ml). Islet insulin content was 35% lower in PHG and 35% higher in mPHG vs controls (P < 0.01). Insulin secretion and maximally stimulated insulin release were also reduced (P < 0.05) in PHG islets due to lower islet insulin content. Isolated PHG islets also had 63% greater (P < 0.01) reactive oxygen species (ROS) accumulation at 11.1 mmol/l glucose than controls (P < 0.01), but oxidative damage was not detected in islet proteins. PHG fetuses showed evidence of oxidative damage to skeletal muscle proteins (P < 0.05) but not insulin resistance. Our findings show that PHG induced dysregulation of islet ROS handling and decreased islet insulin content, but these outcomes are independent. The β-cell outcomes were dependent on the severity of hyperglycemia because mPHG fetuses had no distinguishable impairments in ROS handling or insulin secretion but greater insulin content.
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Affiliation(s)
- Alice S. Green
- Department of Animal Sciences, University of Arizona, Tucson AZ
| | - Xiaochuan Chen
- Department of Animal Sciences, University of Arizona, Tucson AZ
| | - Antoni R. Macko
- Department of Animal Sciences, University of Arizona, Tucson AZ
| | | | - Amy C. Kelly
- Department of Animal Sciences, University of Arizona, Tucson AZ
| | - Nathaniel J. Hart
- Departments of Pharmacology and Physiology, University of Arizona, Tucson AZ
| | - Ronald M. Lynch
- Departments of Pharmacology and Physiology, University of Arizona, Tucson AZ
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32
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Brabez N, Lynch RM, Xu L, Gillies RJ, Chassaing G, Lavielle S, Hruby VJ. Design, synthesis, and biological studies of efficient multivalent melanotropin ligands: tools toward melanoma diagnosis and treatment. J Med Chem 2011; 54:7375-84. [PMID: 21928837 DOI: 10.1021/jm2009937] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To achieve early detection and specific cancer treatment, we propose the use of multivalent interactions in which a series of binding events leads to increased affinity and consequently to selectivity. Using melanotropin (MSH) ligands, our aim is to target melanoma cells which overexpress melanocortin receptors. In this study, we report the design and efficient synthesis of new trivalent ligands bearing MSH ligands. Evaluation of these multimers on a cell model engineered to overexpress melanocortin 4 receptors (MC4R) showed up to a 350-fold increase in binding compared to the monomer, resulting in a trivalent construct with nanomolar affinity starting from a micromolar affinity ligand. Cyclic adenosine monophosphate (cAMP) production was also investigated, leading to more insights into the effects of multivalent compounds on transduction mechanisms.
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Affiliation(s)
- Nabila Brabez
- UPMC Paris06, UMR 7203, Laboratoire des BioMolécules, Université P. et M. Curie, 75005 Paris France
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Josan JS, Handl HL, Sankaranarayanan R, Xu L, Lynch RM, Vagner J, Mash EA, Hruby VJ, Gillies RJ. Cell-specific targeting by heterobivalent ligands. Bioconjug Chem 2011; 22:1270-8. [PMID: 21639139 DOI: 10.1021/bc1004284] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Current cancer therapies exploit either differential metabolism or targeting to specific individual gene products that are overexpressed in aberrant cells. The work described herein proposes an alternative approach--to specifically target combinations of cell-surface receptors using heteromultivalent ligands ("receptor combination approach"). As a proof-of-concept that functionally unrelated receptors can be noncovalently cross-linked with high avidity and specificity, a series of heterobivalent ligands (htBVLs) were constructed from analogues of the melanocortin peptide ligand ([Nle(4), dPhe(7)]-α-MSH) and the cholecystokinin peptide ligand (CCK-8). Binding of these ligands to cells expressing the human Melanocortin-4 receptor and the Cholecystokinin-2 receptor was analyzed. The MSH(7) and CCK(6) were tethered with linkers of varying rigidity and length, constructed from natural and/or synthetic building blocks. Modeling data suggest that a linker length of 20-50 Å is needed to simultaneously bind these two different G-protein coupled receptors (GPCRs). These ligands exhibited up to 24-fold enhancement in binding affinity to cells that expressed both (bivalent binding), compared to cells with only one (monovalent binding) of the cognate receptors. The htBVLs had up to 50-fold higher affinity than that of a monomeric CCK ligand, i.e., Ac-CCK(6)-NH(2). Cell-surface targeting of these two cell types with labeled heteromultivalent ligand demonstrated high avidity and specificity, thereby validating the receptor combination approach. This ability to noncovalently cross-link heterologous receptors and target individual cells using a receptor combination approach opens up new possibilities for specific cell targeting in vivo for therapy or imaging.
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Affiliation(s)
- Jatinder S Josan
- Department of Chemistry & Biochemistry, 1306 E. University Blvd., The University of Arizona, Tucson, Arizona 85721, United States
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34
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Ananthakrishnan K, Weber CS, Hart N, Vagner J, Limesand S, Lynch RM. TARGETING DIABETES: HIGH SPECIFICITY BINDING OF A YOHIMBINE LINKED GLP‐1 DIVALENT LIGAND TO PANCREATIC B‐CELLS. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1063.6] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Abstract
The use of fluorescent (or luminescent) and metal contrast agents in high-throughput screens, in vitro assays, and molecular imaging procedures has rapidly expanded in recent years. Here we describe the development and utility of high-affinity ligands for cancer theranostics and other in vitro screening -studies. In this context, we also illustrate the syntheses and use of heteromultivalent ligands as targeted imaging agents.
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37
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Pritchard TJ, Bowman PS, Jefferson A, Tosun M, Lynch RM, Paul RJ. Na(+)-K(+)-ATPase and Ca(2+) clearance proteins in smooth muscle: a functional unit. Am J Physiol Heart Circ Physiol 2010; 299:H548-56. [PMID: 20543086 DOI: 10.1152/ajpheart.00527.2009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The Na(+)-K(+)-ATPase (NKA) can affect intracellular Ca(2+) concentration regulation via coupling to the Na(+)-Ca(2+) exchanger and may be important in myogenic tone. We previously reported that in mice carrying a transgene for the NKA alpha(2)-isoform in smooth muscle (alpha(2sm+)), the alpha(2)-isoform protein as well as the alpha(1)-isoform (not contained in the transgene) increased to similar degrees (2-7-fold). Aortas from alpha(2sm+) mice relaxed faster from a KCl-induced contraction, hypothesized to be related to more rapid Ca(2+) clearance. To elucidate the mechanisms underlying this faster relaxation, we therefore measured the expression and distribution of proteins involved in Ca(2+) clearance. Na(+)-Ca(2+) exchanger, sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), and plasma membrane Ca(2+)-ATPase (PMCA) proteins were all elevated up to approximately fivefold, whereas actin, myosin light chain, and calponin proteins were not changed in smooth muscle from alpha(2sm+) mice. Interestingly, the corresponding Ca(2+) clearance mRNA levels were unchanged. Immunocytochemical data indicate that the Ca(2+) clearance proteins are distributed similarly in wild-type and alpha(2sm+) aorta cells. In studies measuring relaxation half-times from a KCl-induced contraction in the presence of pharmacological inhibitors of SERCA and PMCA, we estimated that together these proteins were responsible for approximately 60-70% of relaxation in aorta. Moreover, the percent contribution of SERCA and PMCA to relaxation rates in alpha(2sm+) aorta was not significantly different from that in wild-type aorta. The coordinate expressions of NKA and Ca(2+) clearance proteins without change in the relative contributions of each individual protein to smooth muscle function suggest that NKA may be but one component of a larger functional Ca(2+) clearance system.
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Affiliation(s)
- Tracy J Pritchard
- Molecular and Cellular Physiology, Univ. of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0576, USA
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38
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Weber CS, Vagner J, Josan JS, Gillies R, Lynch RM. Modulation of Cell Specific Signaling by Cross‐Linking Receptors with Multivalent Ligands. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.816.10] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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39
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Hart N, Vagner J, Chung WJ, Weber C, Limesand SW, De Silva CR, Lynch RM. Targeting of Pancreatic β‐Cells With High Specificity Using a Heterobivalent GLP‐1/Glibenclamide Ligand. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.816.9] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Xu L, Vagner J, Josan J, Lynch RM, Morse DL, Baggett B, Han H, Mash EA, Hruby VJ, Gillies RJ. Enhanced targeting with heterobivalent ligands. Mol Cancer Ther 2009; 8:2356-65. [PMID: 19671749 DOI: 10.1158/1535-7163.mct-08-1183] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A novel approach to specifically target tumor cells for detection and treatment is the proposed use of heteromultivalent ligands, which are designed to interact with, and noncovalently crosslink, multiple different cell surface receptors. Although enhanced binding has been shown for synthetic homomultivalent ligands, proof of cross-linking requires the use of ligands with two or more different binding moieties. As proof-of-concept, we have examined the binding of synthetic heterobivalent ligands to cell lines that were engineered to coexpress two different G-protein-coupled human receptors, i.e., the human melanocortin 4 receptor (MC4R) expressed in combination with either the human delta-opioid receptor (deltaOR) or the human cholecystokinin-2 receptor (CCK2R). Expression levels of these receptors were characterized by time-resolved fluorescence saturation binding assays using Europium-labeled ligands; Eu-DPLCE, Eu-NDP-alpha-MSH, and Eu-CCK8 for the deltaOR, MC4R, and CCK2R, respectively. Heterobivalent ligands were synthesized to contain a MC4R agonist connected via chemical linkers to either a deltaOR or a CCK2R agonist. In both cell systems, the heterobivalent constructs bound with much higher affinity to cells expressing both receptors, compared with cells with single receptors or to cells where one of the receptors was competitively blocked. These results indicate that synthetic heterobivalent ligands can noncovalently crosslink two unrelated cell surface receptors, making feasible the targeting of receptor combinations. The in vitro cell models described herein will lead to the development of multivalent ligands for target combinations identified in human cancers.
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Affiliation(s)
- Liping Xu
- Department of Pharmaceutical Analytics, Pharmaceutical Institute, University of Tuebingen, Tuebingen, Germany
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41
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LaPresto L, Barthelson R, Cates J, Brooks HL, Galbraith DW, Lynch RM. Nucleomics: Targeting and Genetic Analysis of Nutrient‐Sensing Cells. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.992.1] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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42
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Tse J, Cai Q, Weber C, Lynch RM, Brooks HL. Reduction of GRP78 increases expression of ATF4, GRP94, GADD153 in mIMCD3 cells. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.970.1] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jonathan Tse
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZ
| | - Qi Cai
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZ
| | - Craig Weber
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZ
| | - Ronald M. Lynch
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZ
| | - Heddwen L. Brooks
- Department of PhysiologyCollege of MedicineUniversity of ArizonaTucsonAZ
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Abstract
Albinism is a genetic defect characterized by a loss of pigmentation. The neurosensory retina, which is not pigmented, exhibits pathologic changes secondary to the loss of pigmentation in the retina pigment epithelium (RPE). How the loss of pigmentation in the RPE causes developmental defects in the adjacent neurosensory retina has not been determined, but offers a unique opportunity to investigate the interactions between these two important tissues. One of the genes that causes albinism encodes for an orphan GPCR (OA1) expressed only in pigmented cells, including the RPE. We investigated the function and signaling of OA1 in RPE and transfected cell lines. Our results indicate that OA1 is a selective L-DOPA receptor, with no measurable second messenger activity from two closely related compounds, tyrosine and dopamine. Radiolabeled ligand binding confirmed that OA1 exhibited a single, saturable binding site for L-DOPA. Dopamine competed with L-DOPA for the single OA1 binding site, suggesting it could function as an OA1 antagonist. OA1 response to L-DOPA was defined by several common measures of G-protein coupled receptor (GPCR) activation, including influx of intracellular calcium and recruitment of β-arrestin. Further, inhibition of tyrosinase, the enzyme that makes L-DOPA, resulted in decreased PEDF secretion by RPE. Further, stimulation of OA1 in RPE with L-DOPA resulted in increased PEDF secretion. Taken together, our results illustrate an autocrine loop between OA1 and tyrosinase linked through L-DOPA, and this loop includes the secretion of at least one very potent retinal neurotrophic factor. OA1 is a selective L-DOPA receptor whose downstream effects govern spatial patterning of the developing retina. Our results suggest that the retinal consequences of albinism caused by changes in melanin synthetic machinery may be treated by L-DOPA supplementation. Albinism is the loss of pigmentation caused by mutations in one of several different genes that alter pigment synthesis by different mechanisms. In the eye, albinism impairs sensory retina development and causes significant vision problems. Regardless of the genetic mutation that causes albinism, the associated vision problems are the same. Interestingly, none of the pigmentation genes are expressed by the sensory retinal cells affected by albinism but by neighboring, retinal pigment epithelial cells (RPE). Furthermore, loss of pigmentation in RPE somehow leads to imprecise retinal development. To investigate this cellular relationship, we studied OA1, which is encoded by a gene in which mutations cause ocular albinism. OA1 is unique among proteins involved with albinism because OA1 is a potential receptor that could participate in signal transduction rather than being a direct member of the pigment synthesis machinery. We show that the ligand for OA1 is L-DOPA, thus removing OA1 from orphan G-protein coupled receptor (GPCR) status. L-DOPA is a by-product of pigment synthesis, indicating that pigment synthesis and OA1 signaling are intertwined. OA1 signaling is highly selective for L-DOPA, and we show that two closely related molecules, dopamine and tyrosine, bind to OA1 but fail to stimulate signaling. We also show that OA1 signaling controls secretion of a potent neuron survival factor. Taken together, our data suggest that all forms of albinism produce the same retinal defects because of a final common pathway through OA1 signaling with downstream effects on RPE neurotrophic factor secretion. Albinism produces retinal defects, and OA1 is an orphan G-protein-coupled receptor that leads to albinism without acting directly on melanin synthesis. Here the ligand is identified and a mechanism is proposed by which the various forms of albinism signal through OA1, resulting in the same retinal phenotype.
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Affiliation(s)
- Vanessa M Lopez
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
| | - Christina L Decatur
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
| | - W. Daniel Stamer
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
- Department of Physiology, The University of Arizona, Tucson, Arizona, United States of America
| | - Ronald M Lynch
- Department of Physiology, The University of Arizona, Tucson, Arizona, United States of America
| | - Brian S McKay
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
- Department of Cell Biology and Anatomy, The University of Arizona, Tucson, Arizona, United States of America
- * To whom correspondence should be addressed. E-mail:
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Abstract
Colocalization, in which images of two or more fluorescent markers are overlaid, and coincidence between the probes is measured or displayed, is a common analytical tool in cell biology. Interpreting the images and the meaning of this identified coincidence is difficult in the absence of basic information about the acquisition parameters. In this commentary, we highlight important factors in the acquisition of images used to demonstrate colocalization, and we discuss the minimum information that authors should include in a manuscript so that a reader can interpret both the fluorescent images and any observed colocalization.
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Affiliation(s)
- David R L Scriven
- Department of Cellular and Physiological Sciences, University of British Columbia, Life Sciences Institute, Vancouver, British Columbia, Canada
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Jefferson A, McGrath R, Landowski T, Lynch RM. Modulation of apoptotic signaling by hexokinase binding to mitochondria in myeloma cells. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.1238.10] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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46
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Lynch RM, Weber CS, Nullmeyer KD, Moore EDW, Paul RJ. Clearance of store-released Ca2+ by the Na+-Ca2+ exchanger is diminished in aortic smooth muscle from Na+-K+-ATPase alpha 2-isoform gene-ablated mice. Am J Physiol Heart Circ Physiol 2008; 294:H1407-16. [PMID: 18192219 DOI: 10.1152/ajpheart.00855.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two alpha-isoforms of the Na+-K+-ATPase are expressed in vascular smooth muscle cells (VSMCs). The alpha 1-isoform is proposed to serve a cytosolic housekeeping role, whereas the alpha 2-isoform modulates Ca2+ storage via coupling to the Na+-Ca2+ exchanger (NCX) in a subsarcolemmal compartment. To evaluate the ramifications of this proposed interaction, Ca2+-store load and the contributions of the primary Ca2+ transporters to Ca2+ clearance were studied in aortic VSMCs from embryonic wild-type (WT) and Na+-K+-ATPase alpha 2-isoform gene-ablated, homozygous null knockout (alpha 2-KO) mice. Ca2+ stores were unloaded by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA) in Ca2+-free media to limit Ca2+ influx. Ca2+ clearance by the plasma membrane Ca2+-ATPase (PMCA), NCX, or mitochondria was selectively inhibited. In WT VSMCs, NCX accounted for 90% of the Ca2+ efflux. In alpha 2-KO VSMCs, preferential clearance of store-released Ca2+ by NCX was lost, whereas PMCA activity was increased. Selective inhibition of the alpha 2-isoform (0.5 microM ouabain for 20 min), before treatment with CPA enhanced the store load in VSMCs from WT, but not alpha 2-KO mice. A subsequent analysis of capacitative Ca2+ entry (CCE) indicated that the magnitude of Ca2+ influx was significantly greater in alpha 2-KO cells. Our findings support the concept of a subsarcolemmal space where the alpha 2-isoform coupled with NCX modulates Ca2+-store function and, thereby, CCE.
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Affiliation(s)
- Ronald M Lynch
- Department of Physiology, University of Arizona, Arizona Health Sciences Ctr., Tucson, AZ 85718, USA.
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Barthelson RA, Lambert GM, Vanier C, Lynch RM, Galbraith DW. Comparison of the contributions of the nuclear and cytoplasmic compartments to global gene expression in human cells. BMC Genomics 2007; 8:340. [PMID: 17894886 PMCID: PMC2048942 DOI: 10.1186/1471-2164-8-340] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Accepted: 09/25/2007] [Indexed: 11/10/2022] Open
Abstract
Background In the most general sense, studies involving global analysis of gene expression aim to provide a comprehensive catalog of the components involved in the production of recognizable cellular phenotypes. These studies are often limited by the available technologies. One technology, based on microarrays, categorizes gene expression in terms of the abundance of RNA transcripts, and typically employs RNA prepared from whole cells, where cytoplasmic RNA predominates. Results Using microarrays comprising oligonucleotide probes that represent either protein-coding transcripts or microRNAs (miRNA), we have studied global transcript accumulation patterns for the HepG2 (human hepatoma) cell line. Through subdividing the total pool of RNA transcripts into samples from nuclei, the cytoplasm, and whole cells, we determined the degree of correlation of these patterns across these different subcellular locations. The transcript and miRNA abundance patterns for the three RNA fractions were largely similar, but with some exceptions: nuclear RNA samples were enriched with respect to the cytoplasm in transcripts encoding proteins associated with specific nuclear functions, such as the cell cycle, mitosis, and transcription. The cytoplasmic RNA fraction also was enriched, when compared to the nucleus, in transcripts for proteins related to specific nuclear functions, including the cell cycle, DNA replication, and DNA repair. Some transcripts related to the ubiquitin cycle, and transcripts for various membrane proteins were sorted into either the nuclear or cytoplasmic fractions. Conclusion Enrichment or compartmentalization of cell cycle and ubiquitin cycle transcripts within the nucleus may be related to the regulation of their expression, by preventing their translation to proteins. In this way, these cellular functions may be tightly controlled by regulating the release of mRNA from the nucleus and thereby the expression of key rate limiting steps in these pathways. Many miRNA precursors were also enriched in the nuclear samples, with significantly fewer being enriched in the cytoplasm. Studies of mRNA localization will help to clarify the roles RNA processing and transport play in the regulation of cellular function.
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Affiliation(s)
- Roger A Barthelson
- Bio5 Institute for Collaborative Bioresearch and Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Georgina M Lambert
- Bio5 Institute for Collaborative Bioresearch and Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Cheryl Vanier
- Department of Biological Sciences, University of Nevada, Las Vegas, Nevada 89154, USA
| | - Ronald M Lynch
- Department of Physiology, University of Arizona, Tucson, Arizona 85721, USA
| | - David W Galbraith
- Bio5 Institute for Collaborative Bioresearch and Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
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Pritchard TJ, Parvatiyar M, Bullard DP, Lynch RM, Lorenz JN, Paul RJ. Transgenic mice expressing Na+-K+-ATPase in smooth muscle decreases blood pressure. Am J Physiol Heart Circ Physiol 2007; 293:H1172-82. [PMID: 17468335 DOI: 10.1152/ajpheart.00279.2007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Na(+)-K(+)-ATPase (NKA) is a transmembrane protein that sets and maintains the electrochemical gradient by extruding three Na(+) in exchange for two K(+). An important physiological role proposed for vascular smooth muscle NKA is the regulation of blood pressure via modulation of vascular smooth muscle contractility (5). To investigate the relations between the level of NKA in smooth muscle and blood pressure, we developed mice carrying a transgene for either the NKA alpha(1)- or alpha(2)-isoform (alpha(1 sm+) or alpha(2 sm+) mice) driven by the smooth muscle-specific alpha-actin promoter SMP8. Interestingly, both alpha-isoforms, the one contained in the transgene and the one not contained, were increased to a similar degree at both protein and mRNA levels. The total alpha-isoform protein was increased from 1.5-fold (alpha(1 sm+) mice) to 7-fold (alpha(2 sm+) mice). The increase in total NKA alpha-isoform protein was accompanied by a 2.5-fold increase in NKA activity in alpha(2 sm+) gastric antrum. Immunocytochemistry of the alpha(1)- and alpha(2)-isoforms in alpha(2 sm+) aortic smooth muscle cells indicated that alpha-isoform distributions were similar to those shown in wild-type cells. alpha(2 sm+) Mice (high expression) were hypotensive (109.9 +/- 1.6 vs. 121.3 +/- 1.4 mmHg; n = 13 and 11, respectively), whereas alpha(1 sm+) mice (low expression) were normotensive (122.7 +/- 2.5 vs. 117.4 +/- 2.3; n = 11 or 12). alpha(2 sm+) Aorta, but not alpha(1 sm+) aorta, relaxed faster from a KCl-induced contraction than wild-type aorta. Our results show that smooth muscle displays unique coordinate expression of the alpha-isoforms. Increasing smooth muscle NKA decreases blood pressure and is dependent on the degree of increased alpha-isoform expression.
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Affiliation(s)
- Tracy J Pritchard
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0576, USA
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Lynch RM, Barthelson R, Cates J, Brooks HL, Galbraith DW. Nucleomics of glucose sensing cells: methodology for cell‐type specific analysis of gene expression. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a476-d] [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] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ronald M. Lynch
- PhysiologyUniversity of Arizona1501 N. Campbell Avenue PO Box 245051TucsonAZ85724
| | - Roger Barthelson
- Plant SciencesUniversity of ArizonaMarley Building 822d, PO box: 210036TucsonAZ85724
| | - Julia Cates
- PhysiologyUniversity of Arizona1501 N. Campbell Avenue PO Box 245051TucsonAZ85724
| | - Heddwen L. Brooks
- PhysiologyUniversity of Arizona1501 N. Campbell Avenue PO Box 245051TucsonAZ85724
| | - David W. Galbraith
- Plant SciencesUniversity of ArizonaMarley Building 822d, PO box: 210036TucsonAZ85724
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50
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Zhou M, Nakatani E, Gronenberg LS, Tokimoto T, Wirth MJ, Hruby VJ, Roberts A, Lynch RM, Ghosh I. Peptide-Labeled Quantum Dots for Imaging GPCRs in Whole Cells and as Single Molecules. Bioconjug Chem 2007; 18:323-32. [PMID: 17373766 DOI: 10.1021/bc0601929] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [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: 11/28/2022]
Abstract
We report a robust and practical method for the preparation of water-soluble luminescent quantum dots (QDs) selectively coupled through an amine or thiol linkage to peptide ligands targeted to G-protein coupling receptors (GPCRs) and demonstrate their utility in whole-cell and single-molecule imaging. We utilized a low molecular weight ( approximately 1200 Da) diblock copolymer with acrylic acids as hydrophilic segments and amido-octyl side chains as hydrophobic segments for facile encapsulation of QDs (QD 595 and QD 514) in aqueous solutions. As proof of principle, these QDs were targeted to the human melanocortin receptor (hMCR) by chemoselectively coupling the polymer-coated QDs to either a hexapeptide analog of alpha-melanocyte stimulating hormone or to the highly potent MT-II ligand containing a unique amine. To label QDs with ligands lacking orthogonal amines, the diblock copolymers were readily modified with water-soluble trioxa-tridecanediamine to incorporate freely available amine functionalities. The amine-functionalized QDs underwent facile reaction with the bifunctional linker NHS-maleimide, allowing for covalent coupling to GPCR-targeted ligands modified with unique cysteines. We demonstrate the utility of these maleimide-functionalized QDs by covalent conjugation to a highly potent Deltorphin-II analog that allowed for selective cell-surface and single-molecule imaging of the human delta-opioid receptor (hDOR).
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MESH Headings
- Cells, Cultured/metabolism
- Fluorescence
- Humans
- Immunoenzyme Techniques
- Kidney/metabolism
- Lipid Bilayers/chemistry
- Metallothionein/chemistry
- Metallothionein/metabolism
- Oligopeptides/chemistry
- Oligopeptides/metabolism
- Peptide Fragments/chemical synthesis
- Peptide Fragments/chemistry
- Peptide Fragments/metabolism
- Polymers/chemistry
- Quantum Dots
- Receptor, Melanocortin, Type 4/chemistry
- Receptor, Melanocortin, Type 4/metabolism
- Receptors, G-Protein-Coupled/chemistry
- Receptors, Opioid, delta/chemistry
- Receptors, Opioid, delta/metabolism
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Affiliation(s)
- Min Zhou
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
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