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Susec M, Sencanski M, Glisic S, Veljkovic N, Pedersen C, Drinovec L, Stojan J, Nøhr J, Vrecl M. Functional characterization of β 2-adrenergic and insulin receptor heteromers. Neuropharmacology 2019; 152:78-89. [PMID: 30707913 DOI: 10.1016/j.neuropharm.2019.01.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 01/01/2019] [Accepted: 01/23/2019] [Indexed: 01/06/2023]
Abstract
This study aimed to functionally characterize β2-adrenergic (β2AR) and insulin receptor (IR) heteromers in regard to β-arrestin 2 (βarr2) recruitment and cAMP signaling and to examine the involvement of the cytoplasmic portion of the IR β chain in heteromerization with β2AR. Evidence for β2AR:IR:βarr2 complex formation and the specificity of the IR:βarr2 interaction was first provided by bioinfomatics analysis. Receptor-heteromer investigation technology (HIT) then provided functional evidence of β2AR:IR heterodimerization by showing isoproterenol-induced but not insulin-induced GFP2-βarr2 recruitment to the β2AR:IR complex; the IR:βarr2 interaction was found to only be constitutive. The constitutive IR:βarr2 BRET signal (BRETconst) was significantly smaller in cells coexpressing IR-RLuc8 and a GFP2-βarr2 1-185 mutant lacking the proposed IR binding domain. β2AR:IR heteromerization also influenced the pharmacological phenotype of β2AR, i.e., its efficacy in recruiting βarr2 and activating cAMP signaling. Evidence suggesting involvement of the cytoplasmic portion of the IR β chain in the interaction with β2AR was provided by BRET2 saturation and HIT assays using an IR 1-1271 stop mutant lacking the IR C-terminal tail region. For the complex consisting of IR 1-1271-RLuc8:β2AR-GFP2, saturation was not reached, most likely reflecting random collisions between IR 1-1271 and β2AR. Furthermore, in the HIT assay, no substantial agonist-induced increase in the BRET2 signal was detected that would be indicative of βarr2 recruitment to the IR 1-1271:β2AR heteromer. Complementary 3D visualization of β2AR:IR provided supporting evidence for stability of the heterotetramer complex and identified amino acid residues involved in β2AR:IR heteromerization. This article is part of the Special Issue entitled 'Receptor heteromers and their allosteric receptor-receptor interactions'.
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Affiliation(s)
- Maja Susec
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Slovenia
| | - Milan Sencanski
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Sanja Glisic
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Nevena Veljkovic
- Center for Multidisciplinary Research, Institute of Nuclear Sciences VINCA, University of Belgrade, Belgrade, Serbia
| | - Christina Pedersen
- Department of Incretin & Islet Biology, Novo Nordisk A/S, Måløv, Denmark
| | - Luka Drinovec
- Department of Condensed Matter Physics, Jožef Stefan Institute, Slovenia
| | - Jurij Stojan
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Jane Nøhr
- Department of Incretin & Islet Biology, Novo Nordisk A/S, Måløv, Denmark
| | - Milka Vrecl
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Slovenia.
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Sharma A, Pooraiiouby R, Guzman B, Vu P, Gulia-Nuss M, Nuss AB. Dynamics of Insulin Signaling in the Black-Legged Tick, Ixodes scapularis. Front Endocrinol (Lausanne) 2019; 10:292. [PMID: 31164865 PMCID: PMC6536706 DOI: 10.3389/fendo.2019.00292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 04/23/2019] [Indexed: 01/05/2023] Open
Abstract
Insulin-like peptides (ILPs) have been identified in several invertebrates, particularly insects, and work on these ILPs has revealed many roles including regulation of energy homeostasis, growth, development, and lifespan to name a few. However, information on arthropod ILPs outside of insects is sparse. Studies of Ixodid tick ILPs are particularly scarce, despite their importance as vectors of infectious agents, most notably Lyme disease. The recent publication of the genome of the black-legged tick, Ixodes scapularis, has advanced opportunities to study this organism from a molecular standpoint, a resource sorely needed for an organism with challenging life history requirements for study in the laboratory, such as a long life cycle and obligate, prolonged, blood-feeding at each life stage. Through bioinformatics searches of the tick genome and other available I. scapularis databases, we identified four putative ILP sequences. Full-length sequences of these ILP transcripts were confirmed, and quantitative RT-PCR was used to examine expression levels of these ILPs in different life stages, feeding states, and adult tissues. This work serves as an initial characterization of ILP expression in ticks and provides the foundation for further exploration of the roles of ILPs in these important arthropod vectors.
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Affiliation(s)
- Arvind Sharma
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
| | - Rana Pooraiiouby
- Department of Agriculture, Veterinary, and Rangeland Sciences, University of Nevada, Reno, NV, United States
| | - Blanca Guzman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
| | - Preston Vu
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
| | - Monika Gulia-Nuss
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
- *Correspondence: Andrew B. Nuss
| | - Andrew B. Nuss
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
- Department of Agriculture, Veterinary, and Rangeland Sciences, University of Nevada, Reno, NV, United States
- Monika Gulia-Nuss
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Sharma A, Nuss AB, Gulia-Nuss M. Insulin-Like Peptide Signaling in Mosquitoes: The Road Behind and the Road Ahead. Front Endocrinol (Lausanne) 2019; 10:166. [PMID: 30984106 PMCID: PMC6448002 DOI: 10.3389/fendo.2019.00166] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/28/2019] [Indexed: 12/18/2022] Open
Abstract
Insulin signaling is a conserved pathway in all metazoans. This pathway contributed toward primordial metazoans responding to a greater diversity of environmental signals by modulating nutritional storage, reproduction, and longevity. Most of our knowledge of insulin signaling in insects comes from the vinegar fly, Drosophila melanogaster, where it has been extensively studied and shown to control several physiological processes. Mosquitoes are the most important vectors of human disease in the world and their control constitutes a significant area of research. Recent studies have shown the importance of insulin signaling in multiple physiological processes such as reproduction, innate immunity, lifespan, and vectorial capacity in mosquitoes. Although insulin-like peptides have been identified and functionally characterized from many mosquito species, a comprehensive review of this pathway in mosquitoes is needed. To fill this gap, our review provides up-to-date knowledge of this subfield.
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Affiliation(s)
- Arvind Sharma
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
| | - Andrew B. Nuss
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
- Department of Agriculture, Veterinary, and Rangeland Sciences, University of Nevada, Reno, NV, United States
- *Correspondence: Andrew B. Nuss
| | - Monika Gulia-Nuss
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, United States
- Monika Gulia-Nuss
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Strand MR, Brown MR, Vogel KJ. Mosquito Peptide Hormones: Diversity, Production, and Function. ADVANCES IN INSECT PHYSIOLOGY 2016; 51:145-188. [PMID: 30662099 PMCID: PMC6338476 DOI: 10.1016/bs.aiip.2016.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Mosquitoes, like other insects, produce a diversity of peptide hormones that are processed from different precursor proteins and have a range of activities. Early studies relied on purification of bioactive peptides for hormone identification, but more recently genomic data have provided the information needed to more comprehensively identify peptide hormone genes and associated receptors. The first part of this chapter summarizes the known or predicted peptide hormones that are produced by mosquitoes. The second part of this chapter discusses the sources of these molecules and their functions.
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Affiliation(s)
- M R Strand
- University of Georgia, Athens, GA, United States
| | - M R Brown
- University of Georgia, Athens, GA, United States
| | - K J Vogel
- University of Georgia, Athens, GA, United States
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Wu M, Dai G, Yao J, Hoyt S, Wang L, Mu J. Potentiation of insulin-mediated glucose lowering without elevated hypoglycemia risk by a small molecule insulin receptor modulator. PLoS One 2015; 10:e0122012. [PMID: 25799496 PMCID: PMC4370409 DOI: 10.1371/journal.pone.0122012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Accepted: 02/10/2015] [Indexed: 12/30/2022] Open
Abstract
Insulin resistance is the key feature of type 2 diabetes and is manifested as attenuated insulin receptor (IR) signaling in response to same levels of insulin binding. Several small molecule IR activators have been identified and reported to exhibit insulin sensitization properties. One of these molecules, TLK19781 (Cmpd1), was investigated to examine its IR sensitizing action in vivo. Our data demonstrate that Cmpd1, at doses that produced minimal efficacy in the absence of insulin, potentiated insulin action during an OGTT in non-diabetic mice and enhanced insulin-mediated glucose lowering in diabetic mice. Interestingly, different from insulin alone, Cmpd1 combined with insulin showed enhanced efficacy and duration of action without increased hypoglycemia. To explore the mechanism underlying the apparent glucose dependent efficacy, tissue insulin signaling was compared in healthy and diabetic mice. Cmpd1 enhanced insulin’s effects on IR phosphorylation in both healthy and diabetic mice. In contrast, the compound potentiated insulin’s effects on Akt phosphorylation in diabetic but not in non-diabetic mice. These differential effects on signaling corresponding to glucose levels could be part of the mechanism for reduced hypoglycemia risk. The in vivo efficacy of Cmpd1 is specific and dependent on IR expression. Results from these studies support the idea of targeting IR for insulin sensitization, which carries low hypoglycemia risk by standalone treatment and could improve the effectiveness of insulin therapies.
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Affiliation(s)
- Margaret Wu
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
| | - Ge Dai
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
| | - Jun Yao
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
| | - Scott Hoyt
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
| | - Liangsu Wang
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
| | - James Mu
- Early Development and Discovery Sciences, Merck Research Laboratories, Merck Sharp & Dohme Corp., Whitehouse Station, NJ 08889, United States of America
- * E-mail:
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Vauquelin G, Hall D, Charlton SJ. 'Partial' competition of heterobivalent ligand binding may be mistaken for allosteric interactions: a comparison of different target interaction models. Br J Pharmacol 2015; 172:2300-15. [PMID: 25537684 DOI: 10.1111/bph.13053] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 10/25/2014] [Accepted: 12/14/2014] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND AND PURPOSE Non-competitive drugs that confer allosteric modulation of orthosteric ligand binding are of increasing interest as therapeutic agents. Sought-after advantages include a ceiling level to drug effect and greater receptor-subtype selectivity. It is thus important to determine the mode of interaction of newly identified receptor ligands early in the drug discovery process and binding studies with labelled orthosteric ligands constitute a traditional approach for this. According to the general allosteric ternary complex model, allosteric ligands that exhibit negative cooperativity may generate distinctive 'competition' curves: they will not reach baseline levels and their nadir will increase in par with the orthosteric ligand concentration. This behaviour is often considered a key hallmark of allosteric interactions. EXPERIMENTAL APPROACH The present study is based on differential equation-based simulations. KEY RESULTS The differential equation-based simulations revealed that the same 'competition binding' pattern was also obtained when a monovalent ligand binds to one of the target sites of a heterobivalent ligand, even if this process is exempt of allosteric interactions. This pattern was not strictly reciprocal when the binding of each of the ligands was recorded. The prominence of this phenomenon may vary from one heterobivalent ligand to another and we suggest that this phenomenon may take place with ligands that have been proposed to bind according to 'two-domain' and 'charnière' models. CONCLUSIONS AND IMPLICATIONS The present findings indicate a familiar experimental situation where bivalency may give rise to observations that could inadvertently be interpreted as allosteric binding. Yet, both mechanisms could be differentiated based on alternative experiments and structural considerations.
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Affiliation(s)
- Georges Vauquelin
- Department Molecular and Biochemical Pharmacology, Vrije Universiteit Brussel, Brussels, Belgium
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Affiliation(s)
- Pierre De Meyts
- Department of Diabetes Biology; Novo Nordisk A/S; Måløv Denmark
- De Meyts R&D Consulting; Kraainem; Belgium
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8
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MHC class I limits hippocampal synapse density by inhibiting neuronal insulin receptor signaling. J Neurosci 2014; 34:11844-56. [PMID: 25164678 DOI: 10.1523/jneurosci.4642-12.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Proteins of the major histocompatibility complex class I (MHCI) negatively regulate synapse density in the developing vertebrate brain (Glynn et al., 2011; Elmer et al., 2013; Lee et al., 2014), but the underlying mechanisms remain largely unknown. Here we identify a novel MHCI signaling pathway that involves the inhibition of a known synapse-promoting factor, the insulin receptor. Dominant-negative insulin receptor constructs decrease synapse density in the developing Xenopus visual system (Chiu et al., 2008), and insulin receptor activation increases dendritic spine density in mouse hippocampal neurons in vitro (Lee et al., 2011). We find that genetically reducing cell surface MHCI levels increases synapse density selectively in regions of the hippocampus where insulin receptors are expressed, and occludes the neuronal insulin response by de-repressing insulin receptor signaling. Pharmacologically inhibiting insulin receptor signaling in MHCI-deficient animals rescues synapse density, identifying insulin receptor signaling as a critical mediator of the tonic inhibitory effects of endogenous MHCI on synapse number. Insulin receptors co-immunoprecipitate MHCI from hippocampal lysates, and MHCI unmasks a cytoplasmic epitope of the insulin receptor that mediates downstream signaling. These results identify an important role for an MHCI-insulin receptor signaling pathway in circuit patterning in the developing brain, and suggest that changes in MHCI expression could unexpectedly regulate neuronal insulin sensitivity in the aging and diseased brain.
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Corbin JA, Bhaskar V, Goldfine ID, Issafras H, Bedinger DH, Lau A, Michelson K, Gross LM, Maddux BA, Kuan HF, Tran C, Lao L, Handa M, Watson SR, Narasimha AJ, Zhu S, Levy R, Webster L, Wijesuriya SD, Liu N, Wu X, Chemla-Vogel D, Lee SR, Wong S, Wilcock D, Rubin P, White ML. Inhibition of insulin receptor function by a human, allosteric monoclonal antibody: a potential new approach for the treatment of hyperinsulinemic hypoglycemia. MAbs 2014; 6:262-72. [PMID: 24423625 PMCID: PMC3929448 DOI: 10.4161/mabs.26871] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Novel therapies are needed for the treatment of hypoglycemia resulting from both endogenous and exogenous hyperinsulinema. To provide a potential new treatment option, we identified XMetD, an allosteric monoclonal antibody to the insulin receptor (INSR) that was isolated from a human antibody phage display library. To selectively obtain antibodies directed at allosteric sites, panning of the phage display library was conducted using the insulin-INSR complex. Studies indicated that XMetD bound to the INSR with nanomolar affinity. Addition of insulin reduced the affinity of XMetD to the INSR by 3-fold, and XMetD reduced the affinity of the INSR for insulin 3-fold. In addition to inhibiting INSR binding, XMetD also inhibited insulin-induced INSR signaling by 20- to 100-fold. These signaling functions included INSR autophosphorylation, Akt activation and glucose transport. These data indicated that XMetD was an allosteric antagonist of the INSR because, in addition to inhibiting the INSR via modulation of binding affinity, it also inhibited the INSR via modulation of signaling efficacy. Intraperitoneal injection of XMetD at 10 mg/kg twice weekly into normal mice induced insulin resistance. When sustained-release insulin implants were placed into normal mice, they developed fasting hypoglycemia in the range of 50 mg/dl. This hypoglycemia was reversed by XMetD treatment. These studies demonstrate that allosteric monoclonal antibodies, such as XMetD, can antagonize INSR signaling both in vitro and in vivo. They also suggest that this class of allosteric monoclonal antibodies has the potential to treat hyperinsulinemic hypoglycemia resulting from conditions such as insulinoma, congenital hyperinsulinism and insulin overdose.
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Affiliation(s)
- John A Corbin
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Vinay Bhaskar
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Ira D Goldfine
- Department of Medicine; University of California; San Francisco, CA USA
| | | | | | - Angela Lau
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | | | - Lisa M Gross
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Betty A Maddux
- Department of Medicine; University of California; San Francisco, CA USA
| | - Hua F Kuan
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Catarina Tran
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Llewelyn Lao
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Masahisa Handa
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Susan R Watson
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | | | - Shirley Zhu
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Raphael Levy
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Lynn Webster
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | | | - Naichi Liu
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Xiaorong Wu
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | | | - Steve R Lee
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Steve Wong
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Diane Wilcock
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Paul Rubin
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
| | - Mark L White
- Preclinical Research; XOMA Corporation; Berkeley, CA USA
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Vauquelin G. Simplified models for heterobivalent ligand binding: when are they applicable and which are the factors that affect their target residence time. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:949-62. [DOI: 10.1007/s00210-013-0881-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/05/2013] [Indexed: 01/27/2023]
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Vauquelin G, Charlton SJ. Exploring avidity: understanding the potential gains in functional affinity and target residence time of bivalent and heterobivalent ligands. Br J Pharmacol 2013; 168:1771-85. [PMID: 23330947 PMCID: PMC3623049 DOI: 10.1111/bph.12106] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 11/05/2012] [Accepted: 11/28/2012] [Indexed: 12/13/2022] Open
Abstract
Bivalent ligands are increasingly important therapeutic agents. Although the naturally occurring antibodies are predominant, it is becoming more common to combine different antibody fragments or even low molecular weight compounds to generate heterobivalent ligands. Such ligands exhibit markedly increased affinity (i.e. avidity) and target residence time when both pharmacophores can bind simultaneously to their target sites. This is because binding of one pharmacophore forces the second tethered one to stay close to its corresponding site. This 'forced proximity' favours its binding and rebinding (once dissociated) to that site. However, rebinding will also take place when the diffusion of freshly dissociated ligands is merely slowed down. The present differential equation-based simulations explore the way both situations affect ligand binding. Both delay the attainment of binding equilibrium (resulting in steep saturation curves) and also increase the target residence time. Competitive ligands are able to interfere in a concentration-dependent manner, although much higher concentrations are required in the 'forced proximity' situation. Also, it is only in that situation that the ligand shows increased affinity. These simulations shed light on two practical consequences. Depending on the pharmacokinetic half-life of the bivalent ligand in the body, it may not have sufficient time to achieve equilibrium with the target. This will result in lower potency than expected, although it would have significant advantages in terms of residence time. In in vitro experiments, the manifestation of steep saturation curves and of accelerated dissociation in the presence of competitive ligands could mistakenly be interpreted as evidence for non-competitive, allosteric interactions.
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Affiliation(s)
- Georges Vauquelin
- Department Molecular and Biochemical Pharmacology, Vrije Universiteit Brussel, Brussels, Belgium.
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Vauquelin G, Van Liefde I. Radioligand dissociation measurements: potential interference of rebinding and allosteric mechanisms and physiological relevance of the biological model systems. Expert Opin Drug Discov 2012; 7:583-95. [DOI: 10.1517/17460441.2012.687720] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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13
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Bhaskar V, Goldfine ID, Bedinger DH, Lau A, Kuan HF, Gross LM, Handa M, Maddux BA, Watson SR, Zhu S, Narasimha AJ, Levy R, Webster L, Wijesuriya SD, Liu N, Wu X, Chemla-Vogel D, Tran C, Lee SR, Wong S, Wilcock D, White ML, Corbin JA. A fully human, allosteric monoclonal antibody that activates the insulin receptor and improves glycemic control. Diabetes 2012; 61:1263-71. [PMID: 22403294 PMCID: PMC3331746 DOI: 10.2337/db11-1578] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Many patients with diabetes mellitus (both type 1 and type 2) require therapy to maintain normal fasting glucose levels. To develop a novel treatment for these individuals, we used phage display technology to target the insulin receptor (INSR) complexed with insulin and identified a high affinity, allosteric, human monoclonal antibody, XMetA, which mimicked the glucoregulatory, but not the mitogenic, actions of insulin. Biophysical studies with cultured cells expressing human INSR demonstrated that XMetA acted allosterically and did not compete with insulin for binding to its receptor. XMetA was found to function as a specific partial agonist of INSR, eliciting tyrosine phosphorylation of INSR but not the IGF-IR. Although this antibody activated metabolic signaling, leading to enhanced glucose uptake, it neither activated Erk nor induced proliferation of cancer cells. In an insulin resistant, insulinopenic model of diabetes, XMetA markedly reduced elevated fasting blood glucose and normalized glucose tolerance. After 6 weeks, significant improvements in HbA(1c), dyslipidemia, and other manifestations of diabetes were observed. It is noteworthy that hypoglycemia and weight gain were not observed during these studies. These studies indicate, therefore, that allosteric monoclonal antibodies have the potential to be novel, ultra-long acting, agents for the regulation of hyperglycemia in diabetes.
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Affiliation(s)
- Vinay Bhaskar
- Preclinical Research Department, XOMA (US) LLC, Berkeley, California, USA.
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Insight into the molecular basis for the kinetic differences between the two insulin receptor isoforms. Biochem J 2012; 440:397-403. [PMID: 21838706 DOI: 10.1042/bj20110550] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
More than 20 years after the description of the two IR (insulin receptor) isoforms, designated IR-A (lacking exon 11) and IR-B (with exon 11), nearly every functional aspect of the alternative splicing both in vitro and in vivo remains controversial. In particular, there is no consensus on the precise ligand-binding properties of the isoforms. Increased affinity and dissociation kinetics have been reported for IR-A in comparison with IR-B, but the opposite results have also been reported. These are not trivial issues considering the reported possible increased mitogenic potency of IR-A, and the reported link between slower dissociation and increased mitogenesis. We have re-examined the ligand-binding properties of the two isoforms using a novel rigorous mathematical analysis based on the concept of a harmonic oscillator. We found that insulin has 1.5-fold higher apparent affinity towards IR-A and a 2-fold higher overall dissociation rate. Analysis based on the model showed increased association (3-fold) and dissociation (2-fold) rate constants for binding site 1 of IR in comparison with IR-B. We also provide a structural interpretation of these findings on the basis of the structure of the IR ectodomain and the proximity of the sequence encoded by exon 11 to the C-terminal peptide that is a critical trans-component of site 1.
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Vauquelin G. Determination of drug–receptor residence times by radioligand binding and functional assays: experimental strategies and physiological relevance. MEDCHEMCOMM 2012. [DOI: 10.1039/c2md20015e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Allen MD, Neumann S, Gershengorn MC. Occupancy of both sites on the thyrotropin (TSH) receptor dimer is necessary for phosphoinositide signaling. FASEB J 2011; 25:3687-94. [PMID: 21705666 DOI: 10.1096/fj.11-188961] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The thyroid-stimulating hormone (TSH) receptor signals via G(s) to produce cAMP and via G(q/11) to produce inositol-1,4,5-trisphosphate, which is degraded to inositol monophosphate (IP1; phosphoinositide signaling). The potency of TSH for cAMP signaling is higher than for phosphoinositide signaling, and it was suggested that there are "spare receptors" for cAMP signaling. In a human embryonic kidney macrophage scavenger receptor-expressing (HEK-EM) 293 model system, there are no spare receptors, but the cells still exhibited 100-fold differences in potencies. Dose responses for TSH-stimulated dissociation of prebound (125)I-TSH (negative cooperativity; EC(50)=70 mU/ml), which requires TSH binding to both sites of the TSH receptor (TSHR) homodimer, and TSH-stimulated IP1 production (EC(50)=50 mU/ml) were indistinguishable. Fluorescence resonance energy transfer (FRET) using tagged receptors showed that TSHR formed homodimers and heterodimers with two binding-deficient mutant TSHRs, L252P and C41S. When L252P or C41S was expressed with TSHR, that is, when TSHR/L252P or TSHR/C41S heterodimers could only bind one TSH, TSH-stimulated IP1 production was decreased relative to cAMP production. The slopes of linear regression analyses comparing fold stimulation by TSH of IP1 vs. cAMP production were 0.044 ± 0.0047, 0.0043 ± 0.0041, and 0.0059 ± 0.0014 for cells expressing TSHR alone, TSHR and L252P, or TSHR and C41S, respectively. We suggest that TSHR coupling to phosphoinositide signaling is dependent on binding 2 molecules of TSH to TSHR homodimer, causing a conformational change allowing coupling to G(q/11).
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Affiliation(s)
- Michael D Allen
- Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-8029, USA
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Gaidukov L, Nager AR, Xu S, Penman M, Krieger M. Glycine dimerization motif in the N-terminal transmembrane domain of the high density lipoprotein receptor SR-BI required for normal receptor oligomerization and lipid transport. J Biol Chem 2011; 286:18452-64. [PMID: 21454587 PMCID: PMC3099662 DOI: 10.1074/jbc.m111.229872] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 03/23/2011] [Indexed: 12/15/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI), a CD36 superfamily member, is an oligomeric high density lipoprotein (HDL) receptor that mediates negatively cooperative HDL binding and selective lipid uptake. We identified in the N-terminal transmembrane (N-TM) domain of SR-BI a conserved glycine dimerization motif, G(15)X(2)G(18)X(3)AX(2)G(25), of which the submotif G(18)X(3)AX(2)G(25) significantly contributes to homodimerization and lipid uptake activity. SR-BI variants were generated by mutations (single or multiple Gly → Leu substitutions) or by replacing the N-TM domain with those from other CD36 superfamily members containing (croquemort) or lacking (lysosomal integral membrane protein (LIMP) II) this glycine motif (chimeras). None of the SR-BI variants exhibited altered surface expression (based on antibody binding) or HDL binding. However, the G15L/G18L/G25L triple mutant exhibited reductions in cell surface homo-oligomerization (>10-fold) and the rate of selective lipid uptake (∼ 2-fold). Gly(18) and Gly(25) were necessary for normal lipid uptake activity of SR-BI and the SR-BI/croquemort chimera. The lipid uptake activity of the glycine motif-deficient SR-BI/LIMP II chimera was low but could be increased by introducing glycines at positions 18 and 25. The rate of lipid uptake mediated by SR-BI/LIMP II chimeras was proportional to the extent of receptor oligomerization. Thus, the glycine dimerization motif G(18)X(3)AX(2)G(25) in the N-TM domain of SR-BI contributes substantially to the homo-oligomerization and lipid transport activity of SR-BI but does not influence the negative cooperativity of HDL binding. Oligomerization-independent binding cooperativity suggests that classic allostery is not involved and that the negative cooperativity is probably the consequence of a "lattice effect" (interligand steric interference accompanying binding to adjacent receptors).
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Affiliation(s)
- Leonid Gaidukov
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Andrew R. Nager
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Shangzhe Xu
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Marsha Penman
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Monty Krieger
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Cornils A, Gloeck M, Chen Z, Zhang Y, Alcedo J. Specific insulin-like peptides encode sensory information to regulate distinct developmental processes. Development 2011; 138:1183-93. [PMID: 21343369 DOI: 10.1242/dev.060905] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
An insulin-like signaling pathway mediates the environmental influence on the switch between the C. elegans developmental programs of reproductive growth versus dauer arrest. However, the specific role of endogenous insulin-like peptide (ILP) ligands in mediating the switch between these programs remains unknown. C. elegans has 40 putative insulin-like genes, many of which are expressed in sensory neurons and interneurons, raising the intriguing possibility that ILPs encode different environmental information to regulate the entry into, and exit from, dauer arrest. These two developmental switches can have different regulatory requirements: here we show that the relative importance of three different ILPs varies between dauer entry and exit. Not only do we find that one ILP, ins-1, ensures dauer arrest under harsh environments and that two other ILPs, daf-28 and ins-6, ensure reproductive growth under good conditions, we also show that daf-28 and ins-6 have non-redundant functions in regulating these developmental switches. Notably, daf-28 plays a more primary role in inhibiting dauer entry, whereas ins-6 has a more significant role in promoting dauer exit. Moreover, the switch into dauer arrest surprisingly shifts ins-6 transcriptional expression from a set of dauer-inhibiting sensory neurons to a different set of neurons, where it promotes dauer exit. Together, our data suggest that specific ILPs generate precise responses to dauer-inducing cues, such as pheromones and low food levels, to control development through stimulus-regulated expression in different neurons.
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Affiliation(s)
- Astrid Cornils
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
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Metzger F, Sajid W, Saenger S, Staudenmaier C, van der Poel C, Sobottka B, Schuler A, Sawitzky M, Poirier R, Tuerck D, Schick E, Schaubmar A, Hesse F, Amrein K, Loetscher H, Lynch GS, Hoeflich A, De Meyts P, Schoenfeld HJ. Separation of fast from slow anabolism by site-specific PEGylation of insulin-like growth factor I (IGF-I). J Biol Chem 2011; 286:19501-10. [PMID: 21460230 DOI: 10.1074/jbc.m110.172189] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Insulin-like growth factor I (IGF-I) has important anabolic and homeostatic functions in tissues like skeletal muscle, and a decline in circulating levels is linked with catabolic conditions. Whereas IGF-I therapies for musculoskeletal disorders have been postulated, dosing issues and disruptions of the homeostasis have so far precluded clinical application. We have developed a novel IGF-I variant by site-specific addition of polyethylene glycol (PEG) to lysine 68 (PEG-IGF-I). In vitro, this modification decreased the affinity for the IGF-I and insulin receptors, presumably through decreased association rates, and slowed down the association to IGF-I-binding proteins, selectively limiting fast but maintaining sustained anabolic activity. Desirable in vivo effects of PEG-IGF-I included increased half-life and recruitment of IGF-binding proteins, thereby reducing risk of hypoglycemia. PEG-IGF-I was equipotent to IGF-I in ameliorating contraction-induced muscle injury in vivo without affecting muscle metabolism as IGF-I did. The data provide an important step in understanding the differences of IGF-I and insulin receptor contribution to the in vivo activity of IGF-I. In addition, PEG-IGF-I presents an innovative concept for IGF-I therapy in diseases with indicated muscle dysfunction.
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Nieland TJ, Xu S, Penman M, Krieger M. Negatively cooperative binding of high-density lipoprotein to the HDL receptor SR-BI. Biochemistry 2011; 50:1818-30. [PMID: 21254782 PMCID: PMC3065119 DOI: 10.1021/bi101657j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Scavenger receptor class B, type I (SR-BI), is a high-density lipoprotein (HDL) receptor, which also binds low-density lipoprotein (LDL), and mediates the cellular selective uptake of cholesteryl esters from lipoproteins. SR-BI also is a coreceptor for hepatitis C virus and a signaling receptor that regulates cell metabolism. Many investigators have reported that lipoproteins bind to SR-BI via a single class of independent (not interacting), high-affinity binding sites (one site model). We have reinvestigated the ligand concentration dependence of (125)I-HDL binding to SR-BI and SR-BI-mediated specific uptake of [(3)H]CE from [(3)H]CE-HDL using an expanded range of ligand concentrations (<1 μg of protein/mL, lower than previously reported). Scatchard and nonlinear least-squares model fitting analyses of the binding and uptake data were both inconsistent with a single class of independent binding sites binding univalent lipoprotein ligands. The data are best fit by models in which SR-BI has either two independent classes of binding sites or one class of sites exhibiting negative cooperativity due to either classic allostery or ensemble effects ("lattice model"). Similar results were observed for LDL. Application of the "infinite dilution" dissociation rate method established that the binding of (125)I-HDL to SR-BI at 4 °C exhibits negative cooperativity. The unexpected complexity of the interactions of lipoproteins with SR-BI should be taken into account when interpreting the results of experiments that explore the mechanism(s) by which SR-BI mediates ligand binding, lipid transport, and cell signaling.
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Affiliation(s)
- Thomas J.F. Nieland
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
- Broad Institute of Harvard and MIT, 7 Cambridge Center, Cambridge, MA 02142
| | - Shangzhe Xu
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Marsha Penman
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
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Nieland TJF, Xu S, Penman M, Krieger M. Negatively cooperative binding of high-density lipoprotein to the HDL receptor SR-BI. Biochemistry 2011. [PMID: 21254782 DOI: 10.1021/bi1011657j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Scavenger receptor class B, type I (SR-BI), is a high-density lipoprotein (HDL) receptor, which also binds low-density lipoprotein (LDL), and mediates the cellular selective uptake of cholesteryl esters from lipoproteins. SR-BI also is a coreceptor for hepatitis C virus and a signaling receptor that regulates cell metabolism. Many investigators have reported that lipoproteins bind to SR-BI via a single class of independent (not interacting), high-affinity binding sites (one site model). We have reinvestigated the ligand concentration dependence of (125)I-HDL binding to SR-BI and SR-BI-mediated specific uptake of [(3)H]CE from [(3)H]CE-HDL using an expanded range of ligand concentrations (<1 μg of protein/mL, lower than previously reported). Scatchard and nonlinear least-squares model fitting analyses of the binding and uptake data were both inconsistent with a single class of independent binding sites binding univalent lipoprotein ligands. The data are best fit by models in which SR-BI has either two independent classes of binding sites or one class of sites exhibiting negative cooperativity due to either classic allostery or ensemble effects ("lattice model"). Similar results were observed for LDL. Application of the "infinite dilution" dissociation rate method established that the binding of (125)I-HDL to SR-BI at 4 °C exhibits negative cooperativity. The unexpected complexity of the interactions of lipoproteins with SR-BI should be taken into account when interpreting the results of experiments that explore the mechanism(s) by which SR-BI mediates ligand binding, lipid transport, and cell signaling.
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Affiliation(s)
- Thomas J F Nieland
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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Hernández Mijares A, Solá Izquierdo E, García Malpartida K, Verge D. [Safety of insulin analogues: what to evaluate, how to do it, and how to interpret the results]. ACTA ACUST UNITED AC 2010; 57:376-80. [PMID: 20621572 DOI: 10.1016/j.endonu.2010.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Revised: 04/26/2010] [Accepted: 05/17/2010] [Indexed: 11/26/2022]
Abstract
The widespread use of insulin analogues is based not only on the pharmacokinetics of these preparations, which is much closer to the physiology of insulin secretion under normal conditions, but also on their safety and effectiveness. The publication of a possible association between the use of a long-acting insulin analogue (glargine) and breast cancer has caused uneasiness among the medical community regarding the safety of these analogues. The mechanism of increased tumor activity of insulin analogues is explained by the fact that they act through insulin receptors (IR) and insulin-like growth factor-1 (IGF-1R), stimulating cell growth and inhibiting apoptosis. There are two major mechanisms: an increase in the binding time of insulin to IR and increased activation of IGF-1R. Therefore, to evaluate the safety of an analogue, the slower dissociation rate from its insulin receptor must be excluded, as well as the increased affinity for the IGF-1 receptor. This is equivalent to an index of mitogenic/metabolic activity of less than 1. These aspects can only be evaluated through study of cell lines and animal testing, which are reductionist models that cannot always be extrapolated to humans. To date, there are no data to question the safety of insulin analogues in general. However, the results of observational studies and some in vitro studies, suggesting a potential risk of mitogenicity with the administration of glargine, have caused some alarm among the medical community. Until now, there are no data to refute or confirm this risk and, therefore, evaluation of the existing data is crucial to obtain objective information.
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Dong M, Lam PCH, Pinon DI, Orry A, Sexton PM, Abagyan R, Miller LJ. Secretin occupies a single protomer of the homodimeric secretin receptor complex: insights from photoaffinity labeling studies using dual sites of covalent attachment. J Biol Chem 2010; 285:9919-9931. [PMID: 20100828 DOI: 10.1074/jbc.m109.089730] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The secretin receptor, a prototypic family B G protein-coupled receptor, forms a constitutive homodimeric complex that is stable even in the presence of hormone. Recently, a model of this agonist-bound receptor was built based on high resolution structures reported for amino-terminal domains of other family members. Although this model provided the best solution for all extant data, including 10 photoaffinity labeling constraints, a new such constraint now obtained with a position 16 photolabile probe was inconsistent with this model. As the secretin receptor forms constitutive homodimers, we explored whether secretin might dock across both protomers of the complex, an observation that could also contribute to the negative cooperativity observed. To directly explore this, we prepared six secretin analogue probes that simultaneously incorporated two photolabile benzoylphenylalanines as sites of covalent attachment, in positions known to label distinct receptor subdomains. Each bifunctional probe was a full agonist that labeled the receptor specifically and saturably, with electrophoretic migration consistent with labeling a single protomer of the homodimeric secretin receptor. No band representing radiolabeled receptor dimer was observed with any bifunctional probe. The labeled monomeric receptor bands were cleaved with cyanogen bromide to demonstrate that both of the photolabile benzoylphenylalanines within a single probe had established covalent adducts with a single receptor in the complex. These data are consistent with a model of secretin occupying a single secretin receptor protomer within the homodimeric receptor complex. A new molecular model accommodating all constraints is now proposed.
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Affiliation(s)
- Maoqing Dong
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259
| | - Polo C-H Lam
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92037; Molsoft LLC, La Jolla, California 92037
| | - Delia I Pinon
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259
| | - Andrew Orry
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92037; Molsoft LLC, La Jolla, California 92037
| | - Patrick M Sexton
- Drug Discovery Biology Laboratory, Monash Institute of Pharmaceutical Sciences, and Department of Pharmacology, Monash University, Parkville 3052, Australia
| | - Ruben Abagyan
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92037; Molsoft LLC, La Jolla, California 92037
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259.
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