2_MechanismsOfHormoneAction Flashcards
What are the various signaling pathways for hormone receptors?
1) enzymatic, 2) channel gating, 3) vesicular trafficking, 4) cell motility, 5) transcription
Where are steroid receptors generally found?
cytosol
Where are thyroid hormone receptors generally found?
nucleus
How are hormone receptors regulated?
by type, by sensitivity, and by abundance
What G proteins are in Family I?
G-alpha-S; G-alpha-olf
What G proteins are in Family II?
G-alpha-I; G-alpha-O; G-beta-gamma-O; G-alpha-T
What G proteins are in Family III?
G-alpha-q
What is the function of G-alpha-S?
activates adeylyl cyclase and activates Ca++
What is the function of G-alpha-olf?
activates adenylyl cyclase
What is the function of G-alpha-I?
inhibits adenylyl cyclase
What is the function of G-alpha-O?
activates phospholipase C-beta
What is the function of G-beta-gamma-O?
activates K+, activates phospholipase C-beta, inactivates Ca++
What is the function of G-alpha-T?
activates cGMP phosphodiesterase in rods
What is the function of G-alpha-Q?
activates phospholipase C-beta
Describe the structure of a GPCR.
7-transmembrane segments; extracellular N-terminus; trimeric G-proteins (alpha/beta/gamma)
Describe the structure of G-alpha?
varies – 28 proteins from 16 genes
Describe the structure of G-beta-gamma.
5-beta and 12-gamma members regarded as 1 unit
Describe the structure of an enzyme-linked hormone receptor.
Signaling complex as a molecular scaffold that is pre-assembled in lipid racts
What are the discussed types of enzyme-linked receptors?
RTK & RATK
How do RTKs & RATKs function?
as dimers
What are the 3 essential receptor components for a steroid receptor?
transcription-regulation domain; DNA-binding domain; steroid-binding domain
What is a hormone-response element?
DNA sequence specific for an intracellular receptor
How do steroid receptors make a transcription facotr?
dimerization
How are nuclear receptors different from steroid receptors in structure?
additional extension in DNA-binding domain
How do nuclear receptors produce a transcription factor?
as monomers, as homodimers, or as heterodimers with RXR
How are nuclear receptors regulated?
by abundance & sensitivity through: 1) spatiotemporal expression, 2) phosphorylation, 3) protein-protein interaction, 4) ubuiquitination, 5) acetylation
How are cell-surface receptors regulated?
1) sequestration, 2) lysosomal down-regulation, 3) inactivation, 4) signaling protein inactivation, 5) production of inhibitory protein
What pathway does Leptin function through?
Jak/STAT
