Feb 27th Flashcards
What is the melanocortin system derived from?
Pro-opiomelanocortin (POMC).
What are the four posttranslational peptides of the melanocortin system?
α-MSH, β-MSH, γ-MSH, and ACTH.
How many melanocortin receptors exist?
Five (MC1R, MC2R, MC3R, MC4R, MC5R).
What kind of receptors are melanocortin receptors?
7-membrane, G-protein-coupled receptors (GPCRs).
What are the two melanocortin antagonists?
Agouti and Agouti-related protein (AGRP).
What are the two proteins that modulate melanocortin activity?
Mahogany and Syndecan-3.
What opioid peptide is produced from POMC but not part of the melanocortin system?
β-Endorphin (pituitary, blocks pain).
posttranslational processing of POMC is tissue-specific because:
- Different POMC peptides produced by different cell types
- Control of range of many physiological functions by same prohormone
- Mutations in POMC gene/processing rare but possible
What effect does α-MSH produced in the brain have?
It inhibits food intake.
What happens when there is a mutation in brain α-MSH?
It results in early-onset diabetes.
How does α-MSH affect skin?
It acts on melanocytes, which influence skin and coat color.
What happens when there is a mutation in α-MSH production in the skin?
It results in altered pigmentation.
Where is MCR (melanocortin receptor) produced?
In the adrenals, skin, brain, and penis.
What is a penile MCR mutation associated with?
Sexual function and dysfunction.
What effect does α-MSH have on skin pigmentation?
It increases dark pigment in the skin.
Which receptor does α-MSH bind to?
MC1R (Melanocortin 1 Receptor).
What signaling pathway does MC1R activation trigger?
G-protein-coupled receptors → cAMP → PKA → CREB.
What transcription factor does the MC1R triggered pathway lead to the synthesis of?
MITF (Microphthalmia-Associated Transcription Factor).
Which genes does MITF influence that affect pigmentation?
Tyr (Tyrosinase) & DCT (Dopachrome Tautomerase).
How does the Agouti protein affect skin pigmentation?
It antagonizes MC1R, leading to yellow pigmentation.
How does the Agouti protein affect the brain?
It antagonizes MC4R, leading to overeating & obesity.
what causes red hair
2 copies of a recessive mutation in the MC1R protein
What receptor mutation is linked to erectile dysfunction?
MC4R mutation.
What type of drugs can be used to treat erectile dysfunction related to MC4R?
α-MSH analogs.