Pituitary Glycoproteins and POMC derived peptides

Question 1

What hormones are secreted by the anterior pituitary?

Answer 1

• *F**SH
• *L**H
• *A**CTH
• *T**SH
• *P**rolactin
• *E**ndorphins
• *G**H
• *M**SH

Question 2

What are the 3 classes of anterior pituitary hormones?

Answer 2

Question 3

Which anterior pituitary hormones are somatotropes?

Answer 3

GH

Prolactin

Question 4

Which anterior pituitary hormones are glycoproteins?

Answer 4

TSH

LH

FSH

hCG (placenta)

Question 5

Which anterior pituitary hormones are POMC derived hormones?

Answer 5

ACTH

Endorphins

MSH

Question 6

What is the role of the alpha and beta subunits in the glycoprotein hormones?

Answer 6

Alpha - receptor transactivation

Beta - receptor specificity

Question 7

What signaling pathway do glycoprotein hormones utilize?

Answer 7

GPCRs

Question 8

What is a non-hypersecretory pituitary adenoma?

Answer 8

Question 9

How could you detect that a person has a non-hypersecretory pituitary adenoma?

Answer 9

Answer to Q: Gonadotropes and thyrotropes

Question 10

How can serum testing for alpha glycoprotein subunit be used as a monitoring and diagnostic tool?

Answer 10

Question 11

True or false - CRH production directly induces the production of ACTH.

Answer 11

False - it induces the production of POMC, which can be hydrolyzed to produce ACTH or 4 other hormones (Beta endorphins, or alpha - beta - or gamma - MSH). Different cells in the CNS produce these hormones so CRH can exert variable effects depending on which cells it stimulates.

Question 12

Answer 12

A - POMC

Question 13

• How is POMC processed to produce ACTH, alpha-beta-and gamma MSH, and beta endorphins?
• What determines which of these hormones is made from POMC in a cell?
• What receptors do each of these hormones bind to?

Answer 13

Question 14

• Where is POMC synthesized?
• What is the major cleavage product of POMC in these locations?

Answer 14

Question 15

Beta Endorphins

• Where does this bind?
• What are its effects once it binds?

Answer 15

Question 16

How are beta endorphins involved in addictive seeking UV - behavior?

Answer 16

Question 17

Answer 17

D - cortisone is similar to cortisol, so it can feedback on higher brain structures and inhibit production of POMC –> decreased alpha MSH

Question 19

Describe how alpha MSH regulates pigmentation.

Answer 19

In keratinocytes, cellular damage from UV light leads to production of p53, which increases POMC transcription. POMC is cleaved to alpha MSH which then binds to the MC1R receptor on melanocytes. This activates G_as GPCR (increase AC activity –> increase cAMP –> increase PKA –> increase CREB –> transcription of eumelanin) which leads to increased production of eumelanin in melanocytes and uptake of eumelanin into keratinocytes to protect against UVB radiation.

Question 20

How does alpha MSH play a role in energy metabolism?

Answer 20

MCR4 mutations that result in receptor deficiency are the most frequent single gene cause of obesity. Increased leptin binding in arcuate nucleus of hypothalamus activates POMC/CART neurons to produce increased alpha MSH, which then binds to MCR4 receptors in hypothalamus satiety centers and promotes feelings of satiety leading to decreased food intake.

Paradoxically, alpha MSH levels are very high in the brains of those with obesity (expected to be low) and alpha MSH levels are low in the brains of those with anorexia nervosa (expected to be high)

Question 21

• When stimulated, MC4R receptors in the parasympathetic preganglionic nuclei of the brainstem have what effect?
• When stimulated, MC4R receptors in the sympathetic preganglionic neurons in the spinal cord have what effect?

Answer 21