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10 Cards in this Set

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  • Back
What is typically the precursor for a small peptide hormone?
A larger protein that gets cleaved into a final active peptide, along with inactive fragments. AVP and ACTH are examples of this.
What cell in the pituitary is responsible for GH production?
What hormone is responsible for stimulating GH synthesis and release?
What hormone opposes the release of GH?
What is the mechanism of stimulation for GH synthesis and release?
GH-RH binds to a somatotroph receptor and couples with the Gs protein. That will activate the secondary messenger pathway (cAMP and PKA) to activate GH transcription in the nucleus and storage into vesicles. PKA will also stimulate Ca influx, which will cause those vesicles to fuse with the membrane and release GH into the circulation.
What is the mechanism of suppression for GH synthesis and secretion?
Somatostatin binds with receptors that couple with the Gi protein, which will activate K+ efflux, hyperpolarizing the plasma membrane and shutting down the Ca influx channels. This will prevent GH secretion.
What is the role of phospholipase A2?
Gi-proteins activate PLA2 that will release arachadonic acid, which can be converted to a variety of eicosanoids.
What is the mechanism of bradykinin on blood vessel endothelium?
Bradykinin binding to its receptor on blood vessel endothelium activates Gi proteins, which indirectly activate PLA2, which releases arachidonic acid , which is converted to prostaglandin I2. That will eventually bind to its own receptors which will couple to Gs-proteins on vascular smooth muscle cells causing relaxation.
How do receptor tyrosine kinases work?
Hormone binds to the receptor, causing receptor dimerization. This activates the two tyrosine kinase domains on the cytoplasmic side, which then phosphorylate each other as well as other downstream proteins. The receptors for insulin and IGF-1 behave in this manner. The prophorylated receptor then activates otehr intracellular signaling pathways.
How do tyrosine kinase-associated receptors work?
They themselves have no enzyme activity. When bound (as a homodimer or heterodimer), each receptor is bound to a tyrosine kinase (JAK), which are activated when the hormone binds to their receptors. The JAKs will then phosphorylate themselves and each other, and STATs will dock on the phosphotyrosines and dissociate. These will migrate to the nucleus and activate transcription.