Kandpal - Signal Transduction and Gene Expression Flashcards
what are 2 types of signals
- to environment = pheromones (sex pheromones)
2. signal for other cells in same organism = hormones, morphogens, and neurotransmitters
what are 4 ways a signal is transmitted
contact-dependent, paracrine, synaptic, and endocrine
what is contact-dependent signaling and when is it used
signal is sent forward or backward physically touching other cell - in development and immune response
what is paracrine signaling and when is it used
uses a local mediator - signals neighboring cells
what is synaptic signaling and when is it used
signaling a specific target (one signal can affect multiple targets) - neurotransmitter
what is endocrine signaling and when is it used
hormone goes into blood stream to signal a whole organism - goes to every cell with that receptor (different types of signals but only specific receptors)
what is autocrine signaling
signals secreted by cell can bind to itself to reinforce developmental decisions (differentiation) - community of cells
in what situation is autocrine signaling more effective
if neighboring cells follow the same development and all respond to same signal (many tumor cells use autocrine)
what is combinatorial signaling
a large number of receptors are expressed in a specific cell at a specific time - the receptor determines the behavior (survive, divide, or differentiate) if signal is gone = apoptosis
what type of signals can pass readily through the plasma membrane
hydrophobic signals
what do hydrophilic signals need in order to go through the plasma membrane
ligands need to bind to receptors on cell surface and transduce an effect
how is nitric oxide NO made
arginine + NADPH -> (nitric oxide synthase) -> citrulline + nitric oxide + NADP+
what is the response when acetylcholine is released by autonomic nerves in the walls of blood vessels
smooth muscle relaxation
what mediates acetylcholine
activation of NO synthase which produces NO inside endothelial cells
what does NO bind to after crossing membrane into smooth muscle cells
guanylyl cyclase
how is cGMP activated to mediate a rapid relaxation of smooth muscle cells
after NO is bound to guanylyl cyclase -> GTP -> cGMP
what is the target protein for protein kinase G (PKG)
phospholipase C-beta dependent IP3 (insoitol triphosphate)
how is PKG activated and what is the effect/response
Protein kinase G (PKG) is inactive until cGMP binds to R site and is phosphorylated at the C site = active PKG
response = PKG can phosphorylate a protein
what does viagra inhibit in the NO signaling pathway
it inhibits phosphodiesterase (PDE5) so Ca2+ levels decrease from accumulation of cyclic nucleotides and cause sustained relaxation of smooth muscle cells allowing blood vessels to expand
what are 2 possible ways nitroglycerine enter the NO signaling pathway
- nitroglycerine is being converted to NO and then binding to guanylyl cyclase
- nitroglycerine is directly modifying the reaction is some way (mechanisms are still unknown)
what do phosphodiesterases (PDE) do
convert cyclic nucleotides (ex. cGMP or cAMP) into nucleotide monophosphates by hydrolyzing them
what happens if phosphodiesterases (PDE) are inhibited
accumulation of cyclic nucleotides (that are not hydrolyzed) -> lower Ca2+ levels -> sustained relaxation of smooth muscle cells (instead of rapid)
what are 3 types of phosphodiestereases and where are the expressed
PDE3- cardiac cells
PDE5 - expandable erectile tissue
PDE6- retina
what are some examples of hydrophobic signals
cortisol, estradiol, thyroxine, testosterone, vitamin D, retinoic acid
what do all the hormone receptors belong to and have in common
nuclear receptor superfamily - all have DNA binding domain = ability to modulate transcription
what is a primary (early) response to steroid hormones
induction of transcription in nucleus (steroid hormone + steroid hormone receptor = binds to receptor-steroid-hormone complex)
what is a secondary (delayed) response to steroid hormones
primary response activates secondary-response genes to transcribe for proteins other than the target protein
what is HSP90
an inhibitor - it binds to ligand-domain until ligand comes in and it dissociates
