Anti-MC5R monoclonal antibody Made to order

alpha-Melanotropin, Ac-Ser(1)-Tyr-Ser-Met-Glu-HiS(6)-Phe(7)-Are-Trp(9)-Gly-Lys-Pro -Val(13)-NH21, is anon-selective endogenous agonist for the melanocortin receptor 5; the receptor present in various peripheral tissues and in the brain, cortex and cerebellum. Most of the synthetic analogs of alpha MSH, including a broadly used and more potent the NDP-alpha MSH peptide, Ac-Ser(1)Tyr-Ser-Nle(4)-GIu-His(6)-D-Phe (7)-Are-Trp(9)-Gly-Lys-Pro-Val(13)-NH2, are also not particularly selective for MC5R. To elucidate physiological functions of the melanocortin receptor 5 in rodents and humans, the receptor subtype selective research tools are needed. We report herein syntheses and pharmacological evaluation in vitro of several analogs of NDP-aMSH which are highly potent and specific agonists for the human MC5R. The new linear peptides, of structures and solubility properties similar to those of the endogenous ligand aMSH, are exemplified by compound 7, Ac-Ser(1)-Tyr-Ser-Met-Glu-Oic(6)-D-4,4'-Bip(7)-Pip(8)-Trp(9)-Gly-Lys-Pro-Val(13)-NH2 (Oic: octahydroindole-2-COOH, 4,4'-Bip: 4,4'-biphenylalanine, Pip: pipecolic acid), shortly NODBP-alpha MSH, which has an IC50 = 0.74 nM (binding assay) and EC50 = 0.41 (cAMP production assay) at hMC5R nM and greater than 3500-fold selectivity with respect to the melanocortin receptors 1b, 3 and 4. A shorter peptide derived from NODBP-alpha MSH: Ac-Nle-Glu-Oic(6)-D-4,4'-Bip(7)-Pip(8)-Trp(9)-NH2 (17) was measured to be an agonist only 10-fold less potent at hMC5R than the full length parent peptide. In the structure of this smaller analog, the Nle-Glu-Oic(6)-D-4,4'-Bip(7)-Pip(8) segment was found to be critical for high agonist potency, while the C-terminal Trp(9) residue was shown to be required for high hMC5R selectivity versus hMC1b,3,4R. (c) 2007 Elsevier Inc. All right reserved.

In birds, alpha-MSH is anorexigenic, but effects on adipose tissue are unknown. Four day-old chicks were intraperitoneally injected with 0 (vehicle), 5, 10, or 50 mu g of alpha-MSH and subcutaneous and abdominal adipose tissue collected at 60 min for RNA isolation (n = 10). Plasma was collected post-euthanasia at 60 and 180 min for measuring non-esterified fatty acids (NEFA) and a-MSH (n = 10). Relative to the vehicle, food intake was reduced in the 50 mu g-treated group. Plasma NEFAs were greater in 10 mu g than vehicle-treated chicks at 3 h. Plasma alpha-MSH was 3.06 +/- 0.57 ng/ml. In subcutaneous tissue, melanocortin receptor 5 (MCSR) mRNA was increased in 10 mu g, MC2R and CCAAT-enhancer-binding protein beta (C/EBP beta) mRNAs increased in 50 mu g, peroxisome proliferator-activated receptor gamma and C/EBP alpha decreased in 5, 10. and 50 mu g, and Ki67 mRNA decreased in 50 pg alpha-MSH-injected chicks, compared to vehicle-injected chicks. In abdominal tissue, adipose triglyceride lipase mRNA was greater in 10 mu g alpha-MSH-than vehicle-treated chicks. Cells isolated from abdominal fat that were treated with 10 and 100 nM alpha-MSH for 4 h expressed more MC5R and perilipin-1 than control cells (n = 6). Cells that received 100 nM alpha-MSH expressed more fatty acid binding protein 4 and comparative gene identification-58 mRNA than control cells. Glycerol-3-phosphate dehydrogenase (G3PDH) activity was greater in cells at 9 days post-differentiation that were treated with 1 and 100 nM alpha-MSH for 4 h than in control cells (n = 3). Results suggest that a-MSH increases lipolysis and reduces adipogenesis in adipose tissue.