| 1. |
- Haugaard-Kedström (published under the name Haugaard-Jönsson), Linda M., et al.
(författare)
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Structural Properties of Relaxin Chimeras: NMR Characterization of the R3/I5 Relaxin Peptide
- 2009
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 1160, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- Relaxin-3 interacts with high potency with three relaxin family peptide receptors (RXFP1, RXFP3, and RXFP4). Therefore, the development of selective agonist and antagonist analogs is important for in vivo studies characterizing the biological significance of the different receptor-ligand systems and for future pharmaceutical applications. Recent reports demonstrated that a peptide selective for RXFP3 and RXFP4 over RXFP1 can be generated by the combination of the relaxin-3 B chain with the A chain from insulin-like peptide 5 (INSL5), creating an R3/I5 chimera. We have used NMR spectroscopy to determine the three-dimensional structure of this peptide to gain structural insights into the consequences of combining chains from two different relaxins. The R3/I5 structure reveals a similar backbone conformation for the relaxin-3 B chain compared to native relaxin-3, and the INSL5 A chain displays a relaxin/insulin-like fold with two parallel helices. The findings indicate that binding and activation of RXFP3 and RXFP4 mainly require the B chain and that the A chain functions as structural support. RXFP1, however, demonstrates a more complex binding mechanism, involving both the A chain and the B chain. The creation of chimeras is a promising strategy for generating new structure-activity data on relaxins.
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| 2. |
- Haugaard-Kedström (published under the name Haugaard-Jönsson), Linda M., et al.
(författare)
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Structure of the human insulin-like peptide 5 and characterization of conserved hydrogen bonds and electrostatic interactions within the relaxin framework
- 2009
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 419, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- INSL5 (insulin-like peptide 5) is a two-chain peptide hormone related to insulin and relaxin. It was recently discovered through searches of expressed sequence tag databases and, although the fulfil biological significance of INSL5 is still being elucidated, high expression in peripheral tissues such as the colon, as well as in the brain and hypothalamus, suggests roles in gut contractility and neuroendocrine signalling. INSL5 activates the relaxin family peptide receptor 4 with high potency and appears to be the endogenous ligand for this receptor, on the basis of overlapping expression profiles and their apparent co-evolution. In the present Study, we have used solution-state NMR to characterize the three-dimensional structure of synthetic human INSL5. The structure reveals an insulin/relaxin-like fold with three helical segments that are braced by three disulfide bonds and enclose a hydrophobic core. Furthermore, we characterized in detail the hydrogen-bond network and electrostatic interactions between charged groups in INSL5 by NMR-monitored temperature and pH titrations and Undertook a comprehensive structural comparison with other members of the relaxin family, thus identifying the conserved structural features of the relaxin fold. The B-chain helix, which is the primary receptor-binding site of the relaxins, is longer in INSL5 than in its close relative relaxin-3. As this feature results in a different positioning of the receptor-activation domain Arg(B23) and Trp(B24), it may be an important contributor to the difference in biological activity observed for these two peptides. Overall, the structural Studies provide mechanistic insights into the receptor selectivity of this important family of hormones.
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| 3. |
- Hossain, M. Akhter, et al.
(författare)
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Synthesis, conformation, and activity of human insulin-like peptide 5 (INSL5)
- 2008
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Ingår i: ChemBioChem (Print). - : Wiley. - 1439-4227 .- 1439-7633. ; 9:11, s. 1816-1822
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-like peptide 5 (INSL5) was first identified through searches of the expressed sequence tags (EST) databases. Primary sequence analysis showed it to be a prepropeptide that was predicted to be processed in vivo to yield a two-chain sequence (A and B) that contained the insulin-like disulfide cross-links. The high affinity interaction between INSL5 and the receptor RXFP4 (GPCR142) coupled with their apparent coevolution and partially overlapping tissue expression patterns strongly suggest that INSL5 is an endogenous ligand for RXFP4. Given that the primary function of the INSL5–RXFP4 pair remains unknown, an effective means of producing sufficient quantities of this peptide and its analogues is needed to systematically investigate its structural and biological properties. A combination of solid-phase peptide synthesis methods together with regioselective disulfide bond formation were used to obtain INSL5. Both chains were unusually resistant to standard synthesis protocols and required highly optimized conditions for their acquisition. In particular, the use of a strong tertiary amidine, DBU, as Nα-deprotection base was required for the successful assembly of the B chain; this highlights the need to consider incomplete deprotection rather than acylation as a cause of failed synthesis. Following sequential disulfide bond formation and chain combination, the resulting synthetic INSL5, which was obtained in good overall yield, was shown to possess a similar secondary structure to human relaxin-3 (H3 relaxin). The peptide was able to inhibit cAMP activity in SK-N-MC cells that expressed the human RXFP4 receptor with a similar activity to H3 relaxin. In contrast, it had no activity on the human RXFP3 receptor. Synthetic INSL5 demonstrates equivalent activity to the recombinant-derived peptide, and will be an important tool for the determination of its biological function.
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| 4. |
- Hossain, M. Akhter, et al.
(författare)
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The A-chain of the human relaxin family peptides has distinct roles in the binding and activation of the different relaxin family peptide receptors
- 2008
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 283:25, s. 17287-17297
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Tidskriftsartikel (refereegranskat)abstract
- The relaxin peptides are a family of hormones that share a structural fold characterized by two chains, A and B, that are cross-braced by three disulfide bonds. Relaxins signal through two different classes of G-protein-coupled receptors (GPCRs), leucine-rich repeat-containing GPCRs LGR7 and LGR8 together with GPCR135 and GPCR142, now referred to as the relaxin family peptide (RXFP) receptors 1-4, respectively. Although key binding residues have been identified in the B-chain of the relaxin peptides, the role of the A-chain in their activity is currently unknown. A recent study showed that INSL3 can be truncated at the N terminus of its A-chain by up to 9 residues without affecting the binding affinity to its receptor RXFP2 while becoming a high affinity antagonist. This suggests that the N terminus of the INSL3 A-chain contains residues essential for RXFP2 activation. In this study, we have synthesized A-chain truncated human relaxin-2 and -3 (H2 and H3) relaxin peptides, characterized their structure by both CD and NMR spectroscopy, and tested their binding and cAMP activities on RXFP1, RXFP2, and RXFP3. In stark contrast to INSL3, A-chain-truncated H2 relaxin peptides lost RXFP1 and RXFP2 binding affinity and concurrently cAMP-stimulatory activity. H3 relaxin A-chain-truncated peptides displayed similar properties on RXFP1, highlighting a similar binding mechanism for H2 and H3 relaxin. In contrast, A-chain-truncated H3 relaxin peptides showed identical activity on RXFP3, highlighting that the B-chain is the sole determinant of the H3 relaxin-RXFP3 interaction. Our results provide new insights into the action of relaxins and demonstrate that the role of the A-chain for relaxin activity is both peptide- and receptor-dependent.
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| 5. |
- Rosengren, K. Johan, et al.
(författare)
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Structural insights into the function of relaxins
- 2009
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 1160, s. 20-26
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Tidskriftsartikel (refereegranskat)abstract
- The relaxin peptide hormones are members of the insulin superfamily and share a structural fold that is characterized by two peptide chains which are cross-braced by three disulfide bonds. On this framework, various amino acid side chains are presented, allowing specific interactions with different receptors. The relaxin receptors belong to two unrelated classes of G-protein-coupled receptors, but interestingly they are not selective for a single relaxin peptide. Relaxin-3, which is considered to be an extreme example of the relaxin family, can activate receptors from both classes and in fact interacts to some degree with all four receptors identified to date. To deduce how changes in the primary sequence can fine-tune the overall structure and thus the ability to interact with the various receptors, we have studied a range of relaxin-like peptides using solution nuclear magnetic resonance analysis. Three-dimensional structures of relaxin-3, insulin-like peptide 3 (INSL3), and INSL5 were determined and revealed a number of interesting features. All peptides showed a significant amount of line-broadening in certain regions, in particular around the intra-A-chain disulfide bond, suggesting that despite the disulfide bonds the fold is rather dynamic. Although the peptides share a common structural core there are significant differences, particularly around the termini. The structural data in combination with mutational studies provide valuable insights into the structure-activity relationships of relaxins.
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| 6. |
- Andersson, Håkan S., et al.
(författare)
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The alpha-defensin salt-bridge induces backbone stability to facilitate folding and confer proteolytic resistance
- 2012
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Ingår i: Amino Acids. - : Springer Science and Business Media LLC. - 0939-4451 .- 1438-2199. ; 43:4, s. 1471-1483
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Tidskriftsartikel (refereegranskat)abstract
- Salt-bridge interactions between acidic and basic amino acids contribute to the structural stability of proteins and to protein-protein interactions. A conserved salt-bridge is a canonical feature of the alpha-defensin antimicrobial peptide family, but the role of this common structural element has not been fully elucidated. We have investigated mouse Paneth cell alpha-defensin cryptdin-4 (Crp4) and peptide variants with mutations at Arg(7) or Glu(15) residue positions to disrupt the salt-bridge and assess the consequences on Crp4 structure, function, and stability. NMR analyses showed that both (R7G)-Crp4 and (E15G)-Crp4 adopt native-like structures, evidence of fold plasticity that allows peptides to reshuffle side chains and stabilize the structure in the absence of the salt-bridge. In contrast, introduction of a large hydrophobic side chain at position 15, as in (E15L)-Crp4 cannot be accommodated in the context of the Crp4 primary structure. Regardless of which side of the salt-bridge was mutated, salt-bridge variants retained bactericidal peptide activity with differential microbicidal effects against certain bacterial cell targets, confirming that the salt-bridge does not determine bactericidal activity per se. The increased structural flexibility induced by salt-bridge disruption enhanced peptide sensitivity to proteolysis. Although sensitivity to proteolysis by MMP7 was unaffected by most Arg(7) and Glu(15) substitutions, every salt-bridge variant was degraded extensively by trypsin. Moreover, the salt-bridge facilitates adoption of the characteristic alpha-defensin fold as shown by the impaired in vitro refolding of (E15D)-proCrp4, the most conservative salt-bridge disrupting replacement. In Crp4, therefore, the canonical alpha-defensin salt-bridge facilitates adoption of the characteristic alpha-defensin fold, which decreases structural flexibility and confers resistance to degradation by proteinases.
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| 7. |
- Göransson, Ulf, et al.
(författare)
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The Conserved Glu in the Cyclotide Cycloviolacin O2 Has a Key Structural Role
- 2009
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Ingår i: ChemBioChem (Print). - : Wiley. - 1439-4227 .- 1439-7633. ; 10:14, s. 2354-2360
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Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are a large family of plant peptides that are characterised by a head-to-tail circular backbone and three disulfide bonds that are arranged in a cystine knot. This unique structural feature, which is referred to as a cyclic cystine knot, gives the cyclotides remarkable stability against chemical and biological degradation. In addition to their natural function as insecticides for plant defence, the cyclotides have a range of bioactivities with pharmaceutical relevance, including cytotoxicity against cancer cell lines. A glutamic acid residue, aside from the invariable disulfide array, is the most conserved feature throughout the cyclotide family, and it has recently been shown to be crucial for biological activity. Here we have used solution-state NMR spectroscopy to determine the three-dimensional structures of the potent cytotoxic cyclotide cycloviolacin O2, and an inactive analogue in which this conserved glutamic acid has been methylated. The structures of the peptides show that the glutamic acid has a key structural role in coordinating a set of hydrogen bonds in native cycloviolacin O2; this interaction is disrupted in the methylated analogue. The proposed mechanism of action of cyclotides is membrane disruption and these results suggest that the glutamic acid is linked to cyclotide function by stabilising the structure to allow efficient aggregation in membranes, rather than in a direct interaction with a target receptor.
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| 8. |
- Haugaard-Kedström, Linda M., et al.
(författare)
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A High-Affinity Peptide Ligand Targeting Syntenin Inhibits Glioblastoma
- 2021
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 64:3, s. 1423-1434
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Tidskriftsartikel (refereegranskat)abstract
- Despite the recent advances in cancer therapeutics, highly aggressive cancer forms, such as glioblastoma (GBM), still have very low survival rates. The intracellular scaffold protein syntenin, comprising two postsynaptic density protein-95/discslarge/zona occludens-1 (PDZ) domains, has emerged as a novel therapeutic target in highly malignant phenotypes including GBM. Here, we report the development of a novel, highly potent, and metabolically stable peptide inhibitor of syntenin, KSL-128114, which binds the PDZ1 domain of syntenin with nanomolar affinity. KSL-128114 is resistant toward degradation in human plasma and mouse hepatic microsomes and displays a global PDZ domain selectivity for syntenin. An X-ray crystal structure reveals that KSL128114 interacts with syntenin PDZ1 in an extended noncanonical binding mode. Treatment with KSL-128114 shows an inhibitory effect on primary GBM cell viability and significantly extends survival time in a patient-derived xenograft mouse model. Thus, KSL-128114 is a novel promising candidate with therapeutic potential for highly aggressive tumors, such as GBM.
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| 9. |
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| 10. |
- Haugaard-Kedström (published under the name Haugaard-Jönsson), Linda M., et al.
(författare)
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Structure of the R3/I5 chimeric relaxin peptide, a selective GPCR135 and GPCR142 agonist
- 2008
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 283:35, s. 23811-23818
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Tidskriftsartikel (refereegranskat)abstract
- The human relaxin family comprises seven peptide hormones with various biological functions mediated through interactions with G-protein-coupled receptors. Interestingly, among the hitherto characterized receptors there is no absolute selectivity toward their primary ligand. The most striking example of this is the relaxin family ancestor, relaxin-3, which is an agonist for three of the four currently known relaxin receptors: GPCR135, GPCR142, and LGR7. Relaxin-3 and its endogenous receptor GPCR135 are both expressed predominantly in the brain and have been linked to regulation of stress and feeding. However, to fully understand the role of relaxin-3 in neurological signaling, the development of selective GPCR135 agonists and antagonists for in vivo studies is crucial. Recent reports have demonstrated that such selective ligands can be achieved by making chimeric peptides comprising the relaxin-3 B-chain combined with the INSL5 A-chain. To obtain structural insights into the consequences of combining A-and B-chains from different relaxins we have determined the NMR solution structure of a human relaxin-3/INSL5 chimeric peptide. The structure reveals that the INSL5 A-chain adopts a conformation similar to the relaxin-3 A-chain, and thus has the ability to structurally support a native-like conformation of the relaxin-3 B-chain. These findings suggest that the decrease in activity at the LGR7 receptor seen for this peptide is a result of the removal of a secondary LGR7 binding site present in the relaxin-3 A-chain, rather than conformational changes in the primary B-chain receptor binding site.
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