Details

Autor(en) / Beteiligte

• Hoglin, Brianne E.
• Miner, Marin V.
• Erbenebayar, Uguumur
• Shaughnessy, Ciaran A.
• Dores, Robert M.

Titel

Trends in the evolution of the elasmobranch melanocortin-2 receptor: Insights from structure/function studies on the activation of whale shark Mc2r

Ist Teil von

• General and comparative endocrinology, 2023-07, Vol.338, p.114278-114278, Article 114278

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2023

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• •ACTH(1–24) analog analysis indicated that W9 and R8 are involved in the activation of wsMc2r.•ACTH(1–24) analog analysis indicated that W9, R8, and F7 are involved in the activation of bfMc2r.•Alanine substitution of the KKRRP motif in ACTH(1–24) completely blocked activation of bfMc2r.•Alanine substitution of the KKRRP motif in ACTH(1–24) partially blocked activation of wsMc2r.•The EC2 domain of wsMc2r does not appear to be involved in activation of wsMc2r. To understand the mechanism for activation of the melanocortin-2 receptor (Mc2r) of the elasmobranch, Rhincodon typus (whale shark; ws), wsmc2r was co-expressed with wsmrap1 in CHO cells, and the transfected cells were stimulated with alanine-substituted analogs of ACTH(1–24) at the “message” motif (H6F7R8W9) and the “address” motif (K15K16R17R18P19). Complete alanine substitution of the H6F7R8W9 motif blocked activation, whereas single alanine substitution at this motif indicated the following hierarchy of position importance for activation: W9 > R8, and substitution at F7 and H6 had no effect on activation. The same analysis was done on a representative bony vertebrate Mc2r ortholog (Amia calva; bowfin; bf) and the order of position importance for activation was W9 > R8 = F7, (alanine substitution at H6 was negligible). Complete alanine substitution at the K15K16R17R18P19 motif resulted in distinct outcomes for wsMc2r and bfMc2r. For bfMc2r, this analog blocked activation-an outcome typical for bony vertebrate Mc2r orthologs. For wsMc2r, this analog resulted in a shift in sensitivity to stimulation of the analog as compared to ACTH(1–24) by two orders of magnitude, but the dose response curve did reach saturation. To evaluate whether the EC2 domain of wsMc2r plays a role in activation, a chimeric wsMc2r was made in which the EC2 domain was replaced with the EC2 domain from a melanocortin receptor that does not interact with Mrap1 (i.e., Xenopus tropicalis Mc1r). This substitution did not negatively impact the activation of the chimeric receptor. In addition, alanine substitution at a putative activation motif in the N-terminal of wsMrap1 did not affect the sensitivity of wsMc2r to stimulation by ACTH(1–24). Collectively, these observations suggest that wsMc2r may only have a HFRW binding site for melanocortin-related ligand which would explain how wsMc2r could be activated by either ACTH or MSH-sized ligands.