10. Melanocortinin sys Flashcards
What is the parent gene for ACTH?
POMC - proopiomelanocorticotropin
Describe the following types of components of the melanocortin sys. how many of each are involved in one POMC gene?
a) melanocortin peptides
b) receptors
c) antagonist
d) modulators
e) opioid peptide
a) 4 posttranslational peptide products of POMC a-MSH, b-MSH, g-MSH, and ACTH (melanocortin-stimulating hormones)
b) 5 receptors G-coupled protein receptors - MC1R, MC2R, MC3R, MC4R, MC5R (melanocortin receptors)
c) 2
- Agouti = melanocortin antagonist
- AGRP = agouti-related proteins
d) 2 proteins that regulate melanocortin activity = mahogany + syndecan-3
e) 1 opioid peptide that blocks pain = b-endorphin
Match the following components of the melanocortin sys w/ these; MC1R, Agouti, AGRP, MC2R, ACTH, a-MSH, mahogany, MC3R, MC4R, b-MSH, syndecan-3, b-endorphin, MC5R, g-MSH
a) product of POMC - 4
b) melanocortin receptors - 5
c) melanocortin antagonists - 2
d) melanocortin modulators - 2
e) opioid peptide - 1
a) a-MSH, b-MSH, g-MSH, ACTH
b) MC1R, MC2R, MC3R, MC4R, MC5R
c) Agouti, AGRP
d) syndecan-3, mahogany
e) b-endorphin
Match the following melanocortin components w/ the associated tissue
a) a-MSH
b) MC4R
1. Altered pigmentation
2. early onset obestiy
3. sexual fxn/dysfxn
a) 1 + 2
b) 3
Which of the following is associated w/ a-MSH?
a) inhibition of food intake
b) sexual fxn/dysfxn
c) skin pigment
d) a and b
e) a and c
e
Which type of mutation can cause early onset obesity? How?
a) POMC - MCR4 mutation
b) MCR4 is a receptor that binds to a-MSH which inhibits food intake thus if that receptor doesn’t work properly it will causes INC food intake -> obesity
Describe the 5 steps for how a-MSH INC darkening of skin pigmentation using the following terms; a-MSH, MC1R, G-coupled proteins, AC, ATP, cAMP, PKA, CREB, CRE, MITF, E box, tyrosinase/DCT, melanogenic enzymes
- binding = a-MSH binds to MC1R on mem
- Activate signal pathway = G-couped proteins which activate AC. This in turn uses ATP to produce cAMP, which activates PKA allowing for the binding of CREB into the CRE DNA sequence
- synthesis = MITF is transcribed
- Transcription = MITF regulates the transcription of melanogenic enzymes by binding to the E box DNA sequence which transcribes tyrosinase/DCT
- Tyrosinease/DCT influences pigmentation
agouti mice tend to be yellow and obese. What type of mutation causes this? How?
a mutation that causes the overproduction of the agouti protein which is an MCR1 and MCR4 antagonist. This in turn prevents the binding of a-MSH which is necessary for the inhibition of food (MCR4) intake as well as the darkening of skin pigmentation (MCR1)
6% of jaguars have a condition known as melanism what type of mutation is this and what does it cause? How?
a) MC1R mutation
b) causes the receptor to become oversensitive to a-MSH resulting in darker-pigmented skin (black)
What mutation causes red hair in humans?
mutation in 2 recessive mutations in the MC1R
The MC1R is associated w/ which of the following?
a) food intake
b) skin pigmentation
c) sexual fxn
d) a + b
b
The MC4R is associated w/ which of the following?
a) food intake
b) skin pigmentation
c) sexual fxn
d) a + b
a
Describe how PT-141 can be used to treat erectile dysfxn
it is analogous to a-MSH which means it binds ot MC3R and MC4R ans activates the pathway allowing more production of cAMP resulting in INC sex drive
T of F - While PT-141 can be used to treat erectile dysfxn in males it has no effect on females
F - it can act as an aphrodisiac for females
