Date of Award

Winter 3-22-2025

Document Type

Undergraduate Honors Thesis

Degree Name

B.S. in Biological Sciences

Organizational Unit

College of Natural Science and Mathematics, Biological Sciences

First Advisor

Robert M. Dores

Second Advisor

Joe Angleson

Third Advisor

Scott Nichols

Fourth Advisor

Schuyler Van Engelenburg

Copyright Statement / License for Reuse

All Rights Reserved
All Rights Reserved.

Keywords

Melanocortin system, Melanocortin, Receptors, Melanocortin peptides, cAMP PKA pathway, IP3/DAG signal transduction pathway, Eptatretus burgeri, Endocrinology

Abstract

Two putative melanocortin-like genes (tentatively identified as ebMca and ebMcb) were discovered when the Pacific Hagfish Genome Database was updated in 2022. However, before this thesis, there was no clear indication that the hagfish genome contained melanocortin receptors or melanocortin peptides. Our research began by analyzing the deduced amino acid sequences of the two orphan receptors (ebMca and ebMcb), where key characteristics of melanocortin receptors were noted. Subsequently, we inspected the Mca and Mcb receptors of another jawless fish, the marine lamprey (pm). A high primary sequence identity between the lamprey receptors (pmMca and pmMcb) and the putative hagfish receptors was discovered in doing so. These findings provided the first clue that ebMca and ebMcb are melanocortin receptors. The second clue suggested the melanocortin nature of ebMca and ebMcb, in its ability to be activated by melanocortin peptides (matching the ancestral state of melanocortin receptors). This was shown by the robust dose-response curves produced when ebMca and ebMcb were stimulated with Human ACTH(1-24) and Human ACTH(1-13)NH2. Because lamprey melanocortin receptors (and some gnathostome melanocortin receptors) interact with the accessory proteinMrap2, we co-expressed ebMca and ebMcb with ebMrap2 (extracted from the mrap2 gene in the hagfish genome). No significant effect on either receptor was observed. The last part of the thesis investigated two previously undetected putative hagfish peptides: ebACTH(1-34) and ebACTH(1-13)NH2. Stimulation of ebMca and ebMcb with ebACTH(1-34) and ebACTH(1-13)NH2 worked equally well, indicating that hagfish melanocortin receptors are generic. Finally, since the topic of this paper is in endocrinology, we determined that the hagfish melanocortin receptors prefer activation through the cAMP PKA pathway (CRE Luciferase) over the IP3/DAG signal transduction pathway (NFAT Luciferase).

Copyright Date

5-31-2024

Publication Statement

Copyright is held by the author. This work may only be accessed by members of the University of Denver community. The work is provided by permission of the author for individual research purposes only and may not be further copied or distributed. User is responsible for all copyright compliance.

Rights Holder

Emma E. Kuhn

Provenance

Received from Author

File Format

application/pdf

Language

English (eng)

Extent

39 pgs

File Size

2.07 MB

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