Nuclear receptors Flashcards
what is the difference between cell surface and intracellular receptors ?
- cell surface receptors cannot cross membrane
- intracellular can diffuse through membrane
what are the 2 types of hormones ?
- lipophilic (lipid-soluble)
- hydrophilic (water-soluble)
what are properties of lipophilic hormones ?
- lipid soluble
- pass through plasma membrane
- binds to intracellular receptors
- slower than hydrophilic hormones
how do lipophilic hormones work ?
-pass through plasma membrane
- bind to intracellular receptor at target cells
- activate genes that produce new proteins
how do hydrophilic hormones work ?
- bind to receptors on target cell membranes
- activates signal transduction pathway which produces 2nd messenger
- activates existing enzymes
is lipophillic or hydrophilic action faster ?
- hydrophilic
- new proteins are made in lipophilic
which hormones are produced by the gonads?
- androgen, progesterone, estrogens (steroid hormones)
what are corticosteroid hormones and where are they produced ?
- steroid hormones
- 2 types = glucocorticoids and mineralocorticoids
- produced by adrenal gland
what is the function of glucocorticoids and where are they produced ?
- produced by adrenal gland, stimulate glucose production
- produced in adrenal gland
what is the function of mineralocorticoids and where are they produced?
- produced by adrenal gland
- control salt and water balance in kidney
where is thyroid hormone synthesized, and what does it regulate?
- synthesized from tyrosine in thyroid gland
- regulated metabolism
what is the role of Vitamin D3 in the body?
- It regulates ca2+ metabolism and bone growth.
what is Retinoic Acid, and what is its biological significance?
- it is synthesized from Vitamin A
- key roles in vertebrate development.
what are the 2 types of intracellular receptors ?
- cytoplasmic
- nuclear
examples of cytoplasmic receptors ?
- glucocorticoid
- mineralocorticoid
examples of nuclear receptors ?
- estrogen
- progestrone
- thyroid hormone
- retinoic acid
what are the 3 domains in nuclear receptors ?
- transactivation domain (A/B,E)
- DNA binding/dimerization domain (C)
- nuclear localization domain (D)
what is role of transactivation domain ?
- contains ligand binding domain E
- causes conformational change of DNA shape
- initiates transcription
what is role of DNA-binding/dimerisation domain ?
- allows dimerisation of receptors and binding to DNA
what is role of nuclear localization domain (D) ?
- allows receptor to enter nucleus
mechanism of cytoplasmic receptor activation ?
- ligand enters cell + binds to receptor
- binding dislodges regulatory (repressor) protein
- ligand-receptor complex enters nucleus + binds to specific DNA sequence in promoter region
- binding can either activate gene transcription or inhibit it
mechanism of nuclear receptor ?
- lipid-soluble hormones diffuse through the plasma membrane
- bind to nuclear receptors
- hormone-receptor complex binds to a hormone response element on DNA
- this initiates transcription of mRNA
- mRNA binds to ribosome for translation
what kind of hormone carries out mechanism for both cytoplasmic and nuclear receptors ?
- lipophilic need to enter cell
what is the role of aldosterone + where is it produced ?
- produced by adrenal cortex
- regulates Na+ concentration
- type of mineralocorticoid / steroid hormone
what happens when Na+ concentration is too high ?
- Nedd4-2 binds to ENaC
- causes channels to be internalised
- so decreased reabsorption of Na+
- more Na+ lost in urine
what happens when Na+ concentration is too low ?
- aldosterone promotes expression of SGK1
- SGK1 phosphorylates Nedd4-2
- prevents binding to ENaC
- so it remain in membrane so more Na+ reabsorbed
what is the fucntion of ENaC
- epithelium Na+ channel
- reabsorb Na+
