Discovery of Corticotropin Releasing Factor 2 Receptor Selective Sauvagine Analogues for Treatment of Skeletal Muscle Atrophy

Abstract

The corticotropin release factor 2 receptor (CRF2R) has many biological activities including modulation of the stress response. Recently, we have demonstrated that CRF2R activation functions to prevent skeletal muscle wasting resulting from a variety of physiological stimuli. Thus we are interested in identifying CRF2R selective agonists with optimal pharmacological properties for use in treating muscle wasting diseases. Several CRF2R agonists are known including the frog peptide sauvagine (Svg), which display superior pharmacological properties compared to other CRF2R agonists. Unfortunately sauvagine is a nonselective CRFR agonist, thus making it of less utility due to side effects resulting from corticotropin release factor 1 receptor (CRF1R) activation. Because our initial modifications of Svg at position 11 improved CRF2R selectivity, we investigated the role of amino acids at positions 12 and 13 in Svg. We observed that phenylalanine, leucine, isoleucine, threonine, glutamine, histidine, and tyrosine at the 12th position were the strongest promoters of CRF2R selectivity whereas phenylalanine, glutamine, trytophane, tyrosine, valine, isoleucine, leucine, and 2-naphthylalanine were the preferred residues at the 13th position. Selective sauvagine peptides demonstrated improved antiatrophy effects in a mouse-casting model when compared to sauvagine itself. Thus, we demonstrate that the CRF2R selectivity can be improved by optimizing amino acids at positions 12 and 13 (all with proline at position 11) and that the selective sauvagine analogues demonstrate better in vivo efficacy than sauvagine itself.

Corticotropin Releasing Hormone - A GPCR Drug Target

“…[36] While being highly potent for both CRH receptors it does bind with higher affinity to CRHR 2 , it is 5-10 times more potent for these receptors than CRH. [6,8,37] It has been suggested that there is still a sauvagine like ligand in mammals that is yet to be discovered that would be the native ligand for CRHR 2 rather than Urocortin. [38] The only CRHR 1 selective natural ligand identified is ovine CRH (oCRH).…”

Effects of a CRF2R agonist and exercise on mdx and wildtype skeletal muscle

“…31 Recently, it was shown that sauvagine, a nonselective CRFR agonist, completely inhibited muscle atrophy in casted CRF1R knockout mice. 17 However, the same treatment with noncasted mice had no significant effect on muscle mass. 17 Amino acids were substituted in sauvagine and were tested in vivo in wildtype, CRF1R knockout, and CRF2R knockout mice, in both control and casted conditions.…”

“…17 However, the same treatment with noncasted mice had no significant effect on muscle mass. 17 Amino acids were substituted in sauvagine and were tested in vivo in wildtype, CRF1R knockout, and CRF2R knockout mice, in both control and casted conditions. 17 Several CRF2R-selective sauvagine analogs were found to be more effective and potent than sauvagine in preventing atrophy due to casting.…”

“…5,[12][13][14]22 There are two CRFRs; corticotrophin-releasing factor 1 receptor (CRF1R) is found predominately in the brain, whereas corticotrophin-releasing factor 2 receptor (CRF2R) is expressed ubiquitously throughout all tissues. 17 The CRF2R protein is localized in neuromuscular and myotendinous junctions as well as in endomysium and perimysium surrounding muscle fibers in rats, mice, and humans; however, expression was not observed in myocytes. 31 Blood vessels have also been shown to express the CRF2R protein.…”

“…17 Amino acids were substituted in sauvagine and were tested in vivo in wildtype, CRF1R knockout, and CRF2R knockout mice, in both control and casted conditions. 17 Several CRF2R-selective sauvagine analogs were found to be more effective and potent than sauvagine in preventing atrophy due to casting. 17 We hypothesized that the CRF2R agonist would cause an increase in muscle mass in both mdx and wildtype mice.…”