Signalling Flashcards
How types of interactions form between ligands and receptors?
Non-covalent
Steroid hormones bind to ___________ to modify ________
intracellular receptors
gene expression
How do steroid hormones differ from most other signaling molecules?
steroid hormones: bind intracellularly, alter gene expression
most other signaling molecules: bind receptors on cell surface; modify enzyme activity or open ion channels
Why don’t cells always respond the same way to an extracellular signal?
[signal] can vary # of available receptors can vary intracellular 2nd messenger systems may be different types of receptors expressed may be different
Which routes of signal delivery have highest, intermediate, and lowest receptor affinity?
endocrine = highest
intermediate = paracrine
lowest = neuronal
also have contact-dependent
how does nitric oxide signaling in blood vessels work?
Enters endothelial cell, invlved Ach
diffuses out of cell and into smooth muscle cell
binds target protein in smooth muscle cell
relaxes cell
how does signal transduction for steroid hormones work?
steroid hormone binds receptor
changes conformation to expose DNA binding region
can bind to all promoters with complementary sequence
what are four classes of signaling molecules, and example of each?
small, diffusible molecules (CO, NO)
hydrophobic (steroids and eicosnoids bind 2 types of receptors)
hydrophilic (peptides, AA derivatives)
sensory (smell, taste)
what are the three most common cell surface receptors for hydrophilic molecules and eicosinoids?
ion channel linked - neuronal
trimeric g protein - metabolic
enzyme linked
what is an important example of an enzyme linked receptor involved in cell division and differentiation that responds to growth factors?
receptor tyrosine kinase
what happens upon ligand binding to a trimeric g protein receptor? how is the complex inactivated again?
ligan binds
GDP–> GTP on alpha subunit = active
trimeric complex dissociates into 2 active complexes
these two complexes mediate other proteins but stay LINKED to membrane - can move laterally
bind targets, etc
when two subunits rebind alpha, GDP rebinds and trimeric complex is inactive
What does a Gs receptor do?
activates adenylate cyclase, which makes cAMP
cAMP activates PKA
PKA phosphorylates CREB so it can bind CRE sequences in gene promoters
what do Gq receptors do?
activate Phospholipase C, which generates DAG and IP3
Dag activates PKC
IP3 binds gated channels in ER and releases Ca2+
Ca2+ stimulates activated PKC (and CAM kinases)
______ of SH2-SH3_______ bind and activate the _____ monomeric G protein pathway
SH2 domains
Ras
Monomeric G proteins are activated by _____ and turned off by _______
activated by GEFs
turned off by GAPs (–> GAP in activity)
