L64 - Hormone Action + 2nd Messengers

What can occur when hormone sensitivity decreases?

Down regulation of receptors → number or affinity of receptors decreases

• Decrease synthesis of new receptors

• Increase receptor degrading

• Inactivation of receptors

What can occur when hormone sensitivity increases?

Up-Regulation of Receptors → number or affinity of receptors increases

• Increase synthesis of new receptors

• Decrease receptor degrading

• Activation of receptors

What does a classic cell membrane receptor system use?

Secondary messenger

What does a catalytic cell membrane receptor system use?

Enzyme system (ex. kinases)

What does a catalytic intracellular receptor system use?

Cytoplasmic or nuclear receptors

How do G-proteins work?

Active when GTP bound

Stimulatory or Inhibitory

2ndary Messenger Systems:

• Adenylyl Cyclase → cAMP

• Phospholipase C → IP3 + DAG + Ca

What hormones activate the adenylyl cyclase system?

“FLAT PiG” “CAC”

• FSH

• LH

• ADH

• TSH

• PTH

• Glucagon

• CRH/ACTH

• Calcitonin

What hormones activate the Phospholipase C system?

GnRH

GHRH

Angiotensin II

ADH

TRH

Oxytocin

What enzymes are a part of the catalytic cell receptor systems?

Guanylyl Cyclase + Serine/Threonine Kinase Enzymes

What is the pathway of the guanylyl cyclase enzyme system? What hormones activate it?

GTP → cGMP → cGMP-dependent kinase → phosphorylates proteins

Activated by: ANP and NO

What is the pathway of the serine/threonine kinase enzyme system? What hormones activate it?

CaMK + MAPK + Protein Kinase A/C phosphorlyates threonine and serine (which are on target proteins)→ produces physiological actions