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Dhar N, Mohan A, Thakur C, Chandra NR, Dighe RR. Dissecting the structural and functional features of the Luteinizing hormone receptor using receptor specific single chain fragment variables. Mol Cell Endocrinol 2016; 427:1-12. [PMID: 26940038 DOI: 10.1016/j.mce.2016.02.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/27/2016] [Accepted: 02/27/2016] [Indexed: 01/16/2023]
Abstract
The Luteinizing hormone receptor (LHR) has a large extracellular domain (amino acid residues, a.a.1-355) and a transmembrane domain (TMD; a.a. 356-699), essential for hormone binding and signaling, respectively. The LHR hinge region (a.a. 256-355) connects the two domains and acts as an activating switch for the receptor by an unknown mechanism. LHR hinge-specific Single chain fragment variables (ScFv) stimulated cAMP production by the stable and transiently transfected cell lines expressing LHR in a hormone-independent manner and the C-terminal region of LHR hinge (a.a. 313-349) was identified as the probable epitope for one agonistic ScFv. This epitope attained a helical conformation upon agonistic ScFv binding and the activity of the ScFv was dependent on Y331 sulfation. ScFv was also able to activate TMD mutants, D578Y and A593P, reemphasizing the role of TM helix VI in LHR activation.
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Affiliation(s)
- Neha Dhar
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Abhilash Mohan
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Chandrani Thakur
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Nagasuma R Chandra
- Department of Biochemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Rajan R Dighe
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, Karnataka 560012, India.
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Malachowska-Ugarte M, Sperduto C, Ermolovich YV, Sauchuk AL, Jurášek M, Litvinovskaya RP, Straltsova D, Smolich I, Zhabinskii VN, Drašar P, Demidchik V, Khripach VA. Brassinosteroid-BODIPY conjugates: Design, synthesis, and properties. Steroids 2015. [PMID: 26210210 DOI: 10.1016/j.steroids.2015.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Three BS-BODIPY (brassinosteroids-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) conjugates were synthesized and their fluorescent and immunological properties were investigated. Two of the conjugates, having present all the functional groups characteristic of BS, were shown to be potentially useful as biological probes to study involvement of BS into physiological processes in living cells.
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Affiliation(s)
- Magdalena Malachowska-Ugarte
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus; University of Chemistry and Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic
| | - Claudio Sperduto
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus; University of Chemistry and Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic
| | - Yuri V Ermolovich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus
| | - Alina L Sauchuk
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus
| | - Michal Jurášek
- University of Chemistry and Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic
| | - Raisa P Litvinovskaya
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus
| | - Darya Straltsova
- Department of Plant Cell Biology and Bioengineering, Biological Faculty, Belarusian State University, Minsk, Belarus
| | - Igor Smolich
- Department of Plant Cell Biology and Bioengineering, Biological Faculty, Belarusian State University, Minsk, Belarus
| | - Vladimir N Zhabinskii
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus.
| | - Pavel Drašar
- University of Chemistry and Technology, Technická 5, CZ-166 28 Praha 6, Czech Republic
| | - Vadim Demidchik
- Department of Plant Cell Biology and Bioengineering, Biological Faculty, Belarusian State University, Minsk, Belarus
| | - Vladimir A Khripach
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus
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Jiang X, Dias JA, He X. Structural biology of glycoprotein hormones and their receptors: insights to signaling. Mol Cell Endocrinol 2014; 382:424-451. [PMID: 24001578 DOI: 10.1016/j.mce.2013.08.021] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/20/2013] [Accepted: 08/24/2013] [Indexed: 01/18/2023]
Abstract
This article reviews the progress made in the field of glycoprotein hormones (GPH) and their receptors (GPHR) by several groups of structural biologists including ourselves aiming to gain insight into GPH signaling mechanisms. The GPH family consists of four members, with follicle-stimulating hormone (FSH) being the prototypic member. GPH members belong to the cystine-knot growth factor superfamily, and their receptors (GPHR), possessing unusually large N-terminal ectodomains, belong to the G-protein coupled receptor Family A. GPHR ectodomains can be divided into two subdomains: a high-affinity hormone binding subdomain primarily centered on the N-terminus, and a second subdomain that is located on the C-terminal region of the ectodomain that is involved in signal specificity. The two subdomains unexpectedly form an integral structure comprised of leucine-rich repeats (LRRs). Following the structure determination of hCG in 1994, the field of FSH structural biology has progressively advanced. Initially, the FSH structure was determined in partially glycosylated free form in 2001, followed by a structure of FSH bound to a truncated FSHR ectodomain in 2005, and the structure of FSH bound to the entire ectodomain in 2012. Comparisons of the structures in three forms led a proposal of a two-step monomeric receptor activation mechanism. First, binding of FSH to the FSHR high-affinity hormone-binding subdomain induces a conformational change in the hormone to form a binding pocket that is specific for a sulfated-tyrosine found as sTyr 335 in FSHR. Subsequently, the sTyr is drawn into the newly formed binding pocket, producing a lever effect on a helical pivot whereby the docking sTyr provides as the 'pull & lift' force. The pivot helix is flanked by rigid LRRs and locked by two disulfide bonds on both sides: the hormone-binding subdomain on one side and the last short loop before the first transmembrane helix on the other side. The lift of the sTyr loop frees the tethered extracellular loops of the 7TM domain, thereby releasing a putative inhibitory influence of the ectodomain, ultimately leading to the activating conformation of the 7TM domain. Moreover, the data lead us to propose that FSHR exists as a trimer and to present an FSHR activation mechanism consistent with the observed trimeric crystal form. A trimeric receptor provides resolution of the enigmatic, but important, biological roles played by GPH residues that are removed from the primary FSH-binding site, as well as several important GPCR phenomena, including negative cooperativity and asymmetric activation. Further reflection pursuant to this review process revealed additional novel structural characteristics such as the identification of a 'seat' sequence in GPH. Together with the 'seatbelt', the 'seat' enables a common heteodimeric mode of association of the common α subunit non-covalently and non-specifically with each of the three different β subunits. Moreover, it was possible to establish a dimensional order that can be used to estimate LRR curvatures. A potential binding pocket for small molecular allosteric modulators in the FSHR 7TM domain has also been identified.
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Affiliation(s)
- Xuliang Jiang
- EMD Serono Research & Development Institute, Billerica, MA 01821, United States.
| | - James A Dias
- Department of Biomedical Sciences, School of Public Health, University at Albany-SUNY, Albany, NY 12222, United States
| | - Xiaolin He
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, United States
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Majumdar R, Railkar R, Dighe RR. The antibodies against the computationally designed mimic of the glycoprotein hormone receptor transmembrane domain provide insights into receptor activation and suppress the constitutively activated receptor mutants. J Biol Chem 2012; 287:34514-32. [PMID: 22904318 DOI: 10.1074/jbc.m112.355032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The exoloops of glycoprotein hormone receptors (GpHRs) transduce the signal generated by the ligand-ectodomain interactions to the transmembrane helices either through direct hormonal contact and/or by modulating the interdomain interactions between the hinge region (HinR) and the transmembrane domain (TMD). The ligand-induced conformational alterations in the HinRs and the interhelical loops of luteinizing hormone receptor/follicle stimulating hormone receptor/thyroid stimulating hormone receptor were mapped using exoloop-specific antibodies generated against a mini-TMD protein designed to mimic the native exoloop conformations that were created by joining the thyroid stimulating hormone receptor exoloops constrained through helical tethers and library-derived linkers. The antibody against the mini-TMD specifically recognized all three GpHRs and inhibited the basal and hormone-stimulated cAMP production without affecting hormone binding. Interestingly, binding of the antibody to all three receptors was abolished by prior incubation of the receptors with the respective hormones, suggesting that the exoloops are buried in the hormone-receptor complexes. The antibody also suppressed the high basal activities of gain-of-function mutations in the HinRs, exoloops, and TMDs such as those involved in precocious puberty and thyroid toxic adenomas. Using the antibody and point/deletion/chimeric receptor mutants, we demonstrate that changes in the HinR-exoloop interactions play an important role in receptor activation. Computational analysis suggests that the mini-TMD antibodies act by conformationally locking the transmembrane helices by means of restraining the exoloops and the juxta-membrane regions. Using GpHRs as a model, we describe a novel computational approach of generating soluble TMD mimics that can be used to explain the role of exoloops during receptor activation and their interplay with TMDs.
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Affiliation(s)
- Ritankar Majumdar
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560012, India
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Sharma A, Paranjape AN, Rangarajan A, Dighe RR. A monoclonal antibody against human Notch1 ligand-binding domain depletes subpopulation of putative breast cancer stem-like cells. Mol Cancer Ther 2011; 11:77-86. [PMID: 22075160 DOI: 10.1158/1535-7163.mct-11-0508] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Overexpression of Notch receptors and ligands has been associated with various cancers and developmental disorders, making Notch a potential therapeutic target. Here, we report characterization of Notch1 monoclonal antibodies (mAb) with therapeutic potential. The mAbs generated against epidermal growth factor (EGF) repeats 11 to 15 inhibited binding of Jagged1 and Delta-like4 and consequently, signaling in a dose-dependent manner, the antibodies against EGF repeats 11 to 12 being more effective than those against repeats 13 to 15. These data emphasize the role of EGF repeats 11 to 12 in ligand binding. One of the mAbs, 602.101, which specifically recognizes Notch1, inhibited ligand-dependent expression of downstream target genes of Notch such as HES-1, HES-5, and HEY-L in the breast cancer cell line MDA-MB-231. The mAb also decreased cell proliferation and induced apoptotic cell death. Furthermore, exposure to this antibody reduced CD44(Hi)/CD24(Low) subpopulation in MDA-MB-231 cells, suggesting a decrease in the cancer stem-like cell subpopulation. This was confirmed by showing that exposure to the antibody decreased the primary, secondary, and tertiary mammosphere formation efficiency of the cells. Interestingly, effect of the antibody on the putative stem-like cells appeared to be irreversible, because the mammosphere-forming efficiency could not be salvaged even after antibody removal during the secondary sphere formation. The antibody also modulated expression of genes associated with stemness and epithelial-mesenchymal transition. Thus, targeting individual Notch receptors by specific mAbs is a potential therapeutic strategy to reduce the potential breast cancer stem-like cell subpopulation.
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Affiliation(s)
- Ankur Sharma
- Department of Molecular Reproduction Development and Genetics, Indian Institute of Science, Bangalore, India
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Roy S, Setlur S, Gadkari RA, Krishnamurthy HN, Dighe RR. Translational fusion of two beta-subunits of human chorionic gonadotropin results in production of a novel antagonist of the hormone. Endocrinology 2007; 148:3977-86. [PMID: 17478554 DOI: 10.1210/en.2006-1499] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The strategy of translationally fusing the alpha- and beta-subunits of human chorionic gonadotropin (hCG) into a single-chain molecule has been used to produce novel analogs of hCG. Previously we reported expression of a biologically active single-chain analog hCGalphabeta expressed using Pichia expression system. Using the same expression system, another analog, in which the alpha-subunit was replaced with the second beta-subunit, was expressed (hCGbetabeta) and purified. hCGbetabeta could bind to LH receptor with an affinity three times lower than that of hCG but failed to elicit any response. However, it could inhibit response to the hormone in vitro in a dose-dependent manner. Furthermore, it inhibited response to hCG in vivo indicating the antagonistic nature of the analog. However, it was unable to inhibit human FSH binding or response to human FSH, indicating the specificity of the effect. Characterization of hCGalphabeta and hCGbetabeta using immunological tools showed alterations in the conformation of some of the epitopes, whereas others were unaltered. Unlike hCG, hCGbetabeta interacts with two LH receptor molecules. These studies demonstrate that the presence of the second beta-subunit in the single-chain molecule generated a structure that can be recognized by the receptor. However, due to the absence of alpha-subunit, the molecule is unable to elicit response. The strategy of fusing two beta-subunits of glycoprotein hormones can be used to produce antagonists of these hormones.
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Affiliation(s)
- Satarupa Roy
- Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India
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