A series of 7 new human/rat Corticotropin Releasing Hormone (h/r-CRH) analogues were synthesized. The induced alterations include substitution of Phe at position 12 with D-Phe, Leu at positions 14 and 15 with Aib and Met at positions 21 and 38 with Cys(Et) and Cys(Pr). The analogues were tested regarding their binding affinity to the CRH-1 receptor and their activity which is represented by means of percentage of maximum response in comparison to the native molecule. The results indicated that the introduction of Aib, or Cys derivatives although altering the secondary structure of the molecule, did not hinder receptor recognition and binding. 1. Introduction Ever since its identification by Vale et al. [1], Corticotropin Releasing Hormone (CRH) has proven to be a major neuromodulator responsible not only for the secretion of ACTH by the anterior pituitary gland but also for the regulation of the endocrine, autonomic, immunological and behavioral responses to stress [2–4]. Furthermore, this 41-amino acid neuropeptide displays a plethora of additional roles in either physiological homeostasis or pathogenic manifestations varying from the well-established implication on neuropsychiatric disorders [5, 6] to the yet to be clarified actions on various forms of cardiovascular diseases [7] obesity [8] or gut motility [9], among others. A series of studies demonstrating the extent and perplexity of the roles and implications of CRH led to the identification of other peptides appearing to possess a similar role [10–13]. Both the isolation and characterization of the CRH family receptors has been achieved revealing two receptor subtypes, one of them appearing as three splice variants (CRH-R1, CRH-R2α, CRH-R2β, and CRH-R2γ). A binding protein (CRH-BP) was also described [14–18].The most-studied receptor types are CRH-R1, CRH-R2α, and CRH-R2β not only due to their vast distribution but also for their implication in physiological functions or disorders of great importance. CRH-R1 is broadly distributed in the brain and the pituitary gland but also appears in a number of peripheral tissues [19]. It possesses a critical role in mediating the hypophysiotropic action of CRH [20] but furthermore is involved in anxiogenic behaviours, depression and anxiety [21], anorexia and bulimia, drug seeking and withdrawal, and seizure [22, 23]. CRH-R2α is mainly a brain receptor whereas CRH-R2β is largely expressed in the periphery. The role of CRH-R2 is more diverse since it extends from “stress-coping” responses (anxiolysis, hypotension) to gastric emptying, regulation of energy
References
[1]
W. Vale, J. Spiess, C. Rivier, and J. Rivier, “Characterization of a 41-residue ovine hypothalamic peptide that stimulates secretion of corticotropin and β-endorphin,” Science, vol. 213, no. 4514, pp. 1394–1397, 1981.
[2]
W. Vale, C. Rivier, and C. Rivier, “Chemical and biological characterization of corticotropin releasing factor,” Recent Progress in Hormone Research, vol. 39, pp. 245–270, 1983.
[3]
F. A. Antoni, “Hypothalamic control of adrenocorticotropin secretion: advances since the discovery of 41-residue corticotropin-releasing factor,” Endocrine Reviews, vol. 7, no. 4, pp. 351–378, 1986.
[4]
D. N. Orth, “Corticotropin-releasing hormone in humans,” Endocrine Reviews, vol. 13, no. 2, pp. 164–191, 1992.
[5]
F. Holsboer, “The rationale for corticotropin-releasing hormone receptor (CRH-R) antagonists to treat depression and anxiety,” Journal of Psychiatric Research, vol. 33, no. 3, pp. 181–214, 1999.
[6]
A. Erhardt, M. Ising, and M. Ising, “Regulation of the hypothalamic-pituitary-adrenocortical system in patients with panic disorder,” Neuropsychopharmacology, vol. 31, no. 11, pp. 2515–2522, 2006.
[7]
D. G. Parkes, R. S. Weisinger, and C. N. May, “Cardiovascular actions of CRH and urocortin: an update,” Peptides, vol. 22, no. 5, pp. 821–827, 2001.
[8]
J. Raber, S. Chen, L. Mucke, and L. Feng, “Corticotropin-releasing factor and adrenocorticotrophic hormone as potential central mediators of OB effects,” The Journal of Biological Chemistry, vol. 272, no. 24, pp. 15057–15060, 1997.
[9]
P. J. Gilligan, D. W. Robertson, and R. Zaczek, “Corticotropin releasing factor (CRF) receptor modulators: progress and opportunities for new therapeutic agents,” Journal of Medicinal Chemistry, vol. 43, no. 9, pp. 1641–1660, 2000.
[10]
J. Vauhan, C. Donaldson, and C. Donaldson, “Urocortin, a mammalian neuropeptide related to fish urotensin I and to corticotropin-releasing factor,” Nature, vol. 378, no. 6554, pp. 287–292, 1995.
[11]
S. Y. Hsu and A. J. W. Hsueh, “Human stresscopin and stresscopin-related peptide are selective ligands for the type 2 corticotropin-releasing hormone receptor,” Nature Medicine, vol. 7, no. 5, pp. 605–611, 2001.
[12]
T. M. Reyes, K. Lewis, and K. Lewis, “Urocortin II: a member of the corticotropin-releasing factor (CRF) neuropeptide family that is selectively bound by type 2 CRF receptors,” Proceedings of the National Academy of Sciences of the United States of America, vol. 98, no. 5, pp. 2843–2848, 2001.
[13]
K. Lewis, C. Li, and C. Li, “Identification of urocortin III, an additional member of the corticotropin-releasing factor (CRF) family with high affinity for the CRF2 receptor,” Proceedings of the National Academy of Sciences of the United States of America, vol. 98, no. 13, pp. 7570–7575, 2001.
[14]
D. T. Chalmers, T. W. Lovenberg, D. E. Grigoriadis, D. P. Behan, and E. B. De Souza, “Corticotrophin-releasing factor receptors: from molecular biology to drug design,” Trends in Pharmacological Sciences, vol. 17, no. 4, pp. 166–172, 1996.
[15]
W. A. Kostich, A. Chen, K. Sperle, and B. L. Largent, “Molecular identification and analysis of a novel human corticotropin-releasing factor (CRF) receptor: the CRF(2γ) receptor,” Molecular Endocrinology, vol. 12, no. 8, pp. 1077–1085, 1998.
[16]
O. Valdenaire, T. Giller, V. Breu, J. Gottowik, and G. Kilpatrick, “A new functional isoform of the human CRF2 receptor for corticotropin- releasing factor,” Biochimica et Biophysica Acta, vol. 1352, no. 2, pp. 129–132, 1997.
[17]
B. E. DeSouza, W. T. Lovenberg, T. D. Chalmers, et al., “Heterogeneity of corticotropin releasing factor receptors: multiple targets for the treatment of CNS and inflammatory disorders,” Annual Reports in Medicinal Chemistry, vol. 30, pp. 21–30, 1995.
[18]
P. J. Lowry, R. J. Woods, and S. Baigent, “Corticotropin releasing factor and its binding protein,” Pharmacology Biochemistry and Behavior, vol. 54, no. 1, pp. 305–308, 1996.
[19]
R. Chen, K. A. Lewis, M. H. Perrin, and W. W. Vale, “Expression cloning of a human corticotropin-releasing-factor receptor,” Proceedings of the National Academy of Sciences of the United States of America, vol. 90, no. 19, pp. 8967–8971, 1993.
[20]
G. W. Smith, J.-M. Aubry, and J.-M. Aubry, “Corticotropin releasing factor receptor 1-deficient mice display decreased anxiety, impaired stress response, and aberrant neuroendocrine development,” Neuron, vol. 20, no. 6, pp. 1093–1102, 1998.
[21]
L. Facci, D. A. Stevens, M. Pangallo, D. Franceschini, S. D. Skaper, and P. J. L. M. Strijbos, “Corticotropin-releasing factor (CRF) and related peptides confer neuroprotection via type 1 CRF receptors,” Neuropharmacology, vol. 45, no. 5, pp. 623–636, 2003.
[22]
S. C. Heinrichs and Y. Taché, “Therapeutic potential of CRF receptor antagonists: a gut-brain perspective,” Expert Opinion on Investigational Drugs, vol. 10, no. 4, pp. 647–659, 2001.
[23]
Z. Sarnyai, Y. Shaham, and S. C. Heinrichs, “The role of corticotropin-releasing factor in drug addiction,” Pharmacological Reviews, vol. 53, no. 2, pp. 209–243, 2001.
[24]
D. Richard, Q. Lin, and E. Timofeeva, “The corticotropin-releasing factor family of peptides and CRF receptors: their roles in the regulation of energy balance,” European Journal of Pharmacology, vol. 440, no. 2-3, pp. 189–197, 2002.
[25]
G. R. Valdez, “Development of CRF1 receptor antagonists as antidepressants and anxiolytics: progress to date,” CNS Drugs, vol. 20, no. 11, pp. 887–896, 2006.
[26]
P. A. Keller, L. Elfick, J. Garner, J. Morgan, and A. Mccluskey, “Corticotropin releasing hormone: therapeutic implications and medicinal chemistry developments,” Bioorganic and Medicinal Chemistry, vol. 8, no. 6, pp. 1213–1223, 2000.
[27]
N. Gibbs, R. B. Sessions, P. B. Williams, and C. E. Dempsey, “Helix bending in alamethicin: molecular dynamics simulations and amide hydrogen exchange in methanol,” Biophysical Journal, vol. 72, no. 6, pp. 2490–2495, 1997.
[28]
C. Toniolo, G. M. Bonora, and G. M. Bonora, “Conformation of pleionomers of α-aminoisobutyric acid,” Macromolecules, vol. 18, no. 5, pp. 895–902, 1985.
[29]
D. Theodoropoulus, “Synthesis of certain S-substituted L-cysteines,” Acta Chemica Scandinavica, vol. 13, no. 383, p. 384, 1959.
[30]
G. B. Fields and R. L. Noble, “Solid phase peptide synthesis utilizing 9-fluorenylmethoxycarbonyl amino acids,” International Journal of Peptide and Protein Research, vol. 35, no. 3, pp. 161–214, 1990.
[31]
H. Rink, “Solid-phase synthesis of protected peptide fragments using a trialkoxy-diphenyl-methylester resin,” Tetrahedron Letters, vol. 28, no. 33, pp. 3787–3790, 1987.
[32]
K. Barlos, O. Chatzi, D. Gatos, and G. Stavropoulos, “2-Chlorotrityl chloride resin: studies on anchoring of Fmoc-amino acids and peptide cleavage,” International Journal of Peptide and Protein Research, vol. 37, no. 6, pp. 513–520, 1991.
[33]
M. S. Bernatowicz, S. B. Daniels, and H. K？ster, “A comparison of acid labile linkage agents for the synthesis of peptide C-terminal amides,” Tetrahedron Letters, vol. 30, no. 35, pp. 4645–4648, 1989.
[34]
W. K？nig and R. Geiger, “A new method for synthesis of peptides: activation of the carboxyl group with dicyclohexylcarbodiimide using 1-hydroxybenzotriazoles as additives,” Chemische Berichte, vol. 103, no. 3, pp. 788–798, 1970.
[35]
D. Sarantakis, J. Teichman, E. L. Lien, and R. L. Fenichel, “A novel cyclic undecapeptide, WY-40,770, with prolonged growth hormone release inhibiting activity,” Biochemical and Biophysical Research Communications, vol. 73, no. 2, pp. 336–342, 1976.
[36]
R. Knorr, A. Trzeciak, W. Bannwarth, and D. Gillessen, “New coupling reagents in peptide chemistry,” Tetrahedron Letters, vol. 30, no. 15, pp. 1927–1930, 1989.
[37]
E. Kaiser, R. L. Colescott, C. D. Bossinger, and P. I. Cook, “Color test for detection of free terminal amino groups in the solid-phase synthesis of peptides,” Analytical Biochemistry, vol. 34, no. 2, pp. 595–598, 1970.
[38]
T. Vojkovsky, “Detection of secondary amines on solid phase,” Peptide Research, vol. 8, no. 4, pp. 236–237, 1995.
[39]
G. A. Spyroulias, S. Papazacharias, G. Pairas, and P. Cordopatis, “Monitoring the structural consequences of Phe12 D-Phe and Leu15 Aib substitution in human/rat corticotropin releasing hormone: implications for design of CRH antagonists,” European Journal of Biochemistry, vol. 269, no. 24, pp. 6009–6019, 2002.
[40]
J. Pérodin, R. Bouley, and R. Bouley, “Angiotensin II analogues with sulphur-containing side-chains in position 5. A structure-activity relationship study,” Arzneimittel-Forschung/Drug Research, vol. 50, no. 6, pp. 526–529, 2000.
