Hormone Synthesis and Surface Receptors Flashcards
How do insulin and prolactin interact with each other? What is the result of this interaction?
They act synergistically to stimulate mRNA translation of beta-casein.
What feature usually precedes the transcription start site?
The TATA box.
How do Activators affect transcription? What about repressors? (include mechanism)
Activators: bind enhancer DNA seq. = increase transcription
Repressors: bind silencer DNA seq. = decrease transcription
What is responsible for transcribing genes into mRNA?
RNA Polymerase 2
What 6 steps describe RNA processing?
- Splice out introns, leave exons and untranslated regions
- “Cap” 5’ end of RNA
- Add poly A tail to 3’ end
- Export mRNA from nucleus
- Translate mRNA from start codon
- End translation at stop codon
What are the 3 types of coat proteins?
- Coat-associated protein 1 (COP 1)
- Coat-associated protein 2 (COP 2)
- Clathrin
What is the function of coat-associated protein 1 (COP 1)?
Mediate retrograde transport from trans- to cis-Golgi, as well as cis-Golgi to RER.
What is the function of coat-associated protein 2 (COP 2)?
Mediate transfer of vesicles from RER to Golgi.
What is the function of clathrin?
Mediates transfer of vesicles from Golgi and membrane.
What 6 steps outline the process of vesicular secretion?
- Sort which hormones get secreted
- Coat proteins associate
- Vesicle buds and translocates
- Coat proteins dissociate
- v-SNARE/t-SNARE recognition > docking
- Membrane fusion and hormone delivery
What is the purpose of v-SNARE and t-SNARE in vesicular secretion?
Receptors/ligands on vesicle and target membrane which recognize each other and allow docking.
What structural features of mRNA influence its half-life?
The 5’ cap and the length of the 3’ poly A tail.
On a Scatchard plot, which feature denotes Ro (total receptor concentration)?
The x-intercept.
On a Scatchard plot, what does the y-intercept represent?
Ro/KD
Where KD is the concentration of free hormone when 50% of the receptors are bound.
On a Scatchard plot, what does the slope of the graph represent?
-1/KD
Where KD is the concentration of free hormone when 50% of the receptors are bound.
What is pindolol?
A beta-adrenergic antagonist.
What are the 5 types of cell surface receptors (based on structure)?
- 7 Transmembrane domain G protein coupled receptors
- Growth factor receptors
- Cytokine receptors
- Guanylyl cyclase receptors
- Novel cell surface receptors (ex: ferroportin)
What differentiates growth factor receptors (GFRs) from cytokine receptors (CRs)?
GFRs have an attached tyrosine kinase domain while CRs do not, and must recruit accessory proteins with tyrosine kinase domains.
Which part of the 7TM receptor protrudes outside the membrane as the ligand-binding domain? Which part protrudes into the cytoplasm?
The N-terminus is extracellular, the C-terminus is in the cytoplasm.
What differentiates the function of the 3 types of G protein alpha subunits?
Galpha-s: stimulation of adenylate cyclase (AC)
Galpha-i: inhibition of adenylate cyclase (AC)
Galpha-q: stimulation of phospholipase C (PLC)
What 5 steps describe Galpha-s coupled signalling?
- Ligand binds to receptor
- AC activated, produces cAMP from ATP
- cAMP removes inhibitory subunit of PKA
- PKA phosphorylates substrates (CREB)
- CREB binds to DNA, enhances transcription
What does PIP2 become when cleaved? What do these products do?
Inositol triphosphate (IP3): mediates intracellular calcium release Diacylglycerol (DAG): activates protein kinase C (PKC)
What 4 steps describe Galpha-q coupled signalling?
- Ligand binds receptor
- PIP2 cleaved to IP3 and DAG
- Calcium is released with various effects, also PKC is activated
- PKC has many effects, some on transcription
What 4 domains are present in the guanyly cyclase receptor?
- Binding domain
- Transmembrane domain
- Kinase-like domain
- Guanylyl cyclase
What are the 2 major classes of guanylyl cyclase receptors?
- Membrane bound
2. Soluble
What are iNOS and eNOS? What activates these? What do they activate?
Inducible and endothelial nitric oxide synthetase. Activated by GPCR Galpha-q, converted to nitric oxide which activates soluble guanylyl cyclases.
What is hepcidin? What is its main function? What receptor does it bind to?
A polypeptide hormone which controls body iron levels. Binds to ferroportin and causes channel degradation.
