Lecture 18 2/16/24 Flashcards
What is the single parent precursor of hormones in the ACTH family?
POMC
Which molecules are produced when POMC is split roughly in half?
-AACTH
-b-LPH
What must occur in order for AACTH and b-LPH to be secreted?
the two molecules must be separated via hydrolysis and co-secreted by pituitary cells
What can ACTH be hydrolyzed into?
-aMSH
-CLIP
What can b-LPH be hydrolyzed into?
-y-LPH
-b-endorphin
Which amino acids in ACTH are the most important and bioactive?
the first 24 AAs
Why is it important that ACTH is measured via an antibody recognition site in the tail?
-mutated ACTH with a normal bioactive region and abnormal tail can be active in the animal without being detected via assay
-mutated ACTH with a normal tail but abnormal bioactive region can lead to signs of ACTH deficiency while producing normal assay results
What are the potential roles of oxytocin?
-synthetic oxytocin used to reinforce contractions during birth process
-naturally produced oxytocin triggers milk ejection during breastfeeding
What is the primary source of both oxytocin and ADH?
hypothalamus
Which family is ADH classified into?
oxytocin family
What is a receptor?
molecule on the cell surface or within the cell that recognizes and binds with ligands to produce some effect in the cells
What are the characteristics that can vary between different receptors?
-specificity for hormone
-affinity
-saturability
-reversibility of binding
-specific response
What are the characteristics of receptor specificity?
-often HIGH specificity for the hormone/ligand
-can have some overlap with very similar hormones
What are the characteristics of the mineralocorticoid receptor (MR)?
-belongs to cytoplasmic/nuclear receptor family
-activated by mineralocorticoids and glucocorticoids
-protected from glucocorticoids via enzyme that converts cortisol into cortisone
What are the characteristics of receptor affinity?
-strength by which hormone is bound to its receptor
-high affinity receptor requires less hormone to reach 50% receptor saturation
How does affinity relate to concentration?
decreased concentration requires receptor to have increased affinity
How does affinity relate to bioactivity?
increased affinity leads to increased bioactivity
What are the characteristics of receptor saturability?
-number of receptors in a target cell can change by day, or even by minute
-receptor down-regulation leads to decreased target tissue responsiveness
-receptor up-regulation leads to increased target tissue responsiveness
What can lead to receptor down-regulation?
-inactivation of receptor molecules
-inactivation of intracellular protein signaling molecules
-temporary sequestration of receptors
-destruction of receptors via lysosomes
-decreased receptor production
What are the two types of hormone receptor models?
-plasma membrane receptors: bind hormones that cannot enter cell
-intracellular receptors: bind hormones that can freely enter cell
What is signal transduction?
process involving the conversion of a signal from outside the cell to a functional change within the cell
What is the pathway of signal transduction?
-first messenger + membrane receptor leads to series of reactions in cell membrane
-rxns release second messenger into cell
-second messenger leads to biological effect
What are the 4 second messengers?
-cAMP
-IP3
-DAG
-Ca++
What are the characteristics of intracellular hormone receptors?
-floating receptors
-called non-transformed when connected to molecular chaperones
-activated receptors move to DNA and bind
-binding leads to genomic effects
-no second messenger
