Lecture 7 Flashcards
what are most cell signals?
extracellular signaling molecules: any moleculle that can transmit a signal (proteins, hormones, ions, gases)
receptor
binds a signaling molecule, can also be inside cell
ligand
receptors bind to ligands, another word for extracellular signaling molecule that binds to receptors
specific ligand-receptor interaction
intracellular signaling molecules
anything that transmits a signal inside the cell
secondary messenger
subtype of intracellular signaling molecule, any NON-PROTEIN
effector proteins
recieve signal, example: transcriptional regulator
2 types of SHORT DISTANCE extracellular signaling molecules
- contact dependant - membrane bound signal molecule (example - niches for stem cells)
- paracrine - one cell secretes signaling molecule, only travels short distance (example - morphogens)
how are paracrine signals regulated to onlly travel a short distance?
- internalized
- degraded
- limited diffusion
- receptor expression of other cells
autocrine signaling
secretes a signal that can interact with secreting cell
long distance signaling
- synaptic - cell bodies far apart but axon membrane is very close to target membrane
- endocrine cell - signal travels through bloodstream, only cells expressing receptor recieve signal
what are the 2 classes of receptor/ligand interactions
- cell-surface receptors - usually hydrophobic signaling molecule, large TM domain, molecule does not enter
- intracellular receptors - small signal molecule (sometimes with carrier protein) crosses membrane and interacts with target protein inside cell
can phosphorylation change charge? is it reversible?
- yes
- yes
G protein activated when is bound and inactive when is bound
- GTP
- GDP
what is GEF and what does it do
guanine nucleotide exchange factor
exchange GDP for GTP therefore activating the protein
what is GAP and what does it do
GTPase-activating protein
hydrolyze GTP to GDP inactivating G protein
what does polyubiquination indicate to the cell
signals protein for degredation
what does multi ubiquitination do
endocytosis
what does ubiquitination USUALLY do
turns signaling off
how do inhibitor proteins work with transcriptional regulators
bind transcriptional regulator, but when phosphorylated it can’t inhibit. signal signals for kinase to release regulator
all or none switch
even when signal is gone, output/response continues
what does an oscilating output indicate about the signaling pathway
negative feedback
5 types of negatative feedback
- short delay
- long delay
- receptor inactivation
- receptor sequestration
- receptor destruction
can acetylcholine trigger different responses in different cells?
yes! can have same receptor but different downstream effects/effectors or different receptors triggering different downstream signaling
how can cells be specific in a complex of cellular environment?
- signaling complexes
- coincidence detectors
what are scaffold proteins?
binds to several components in signaling pathway bringing them close together and in order (proteins can bind before or after signal)
what are phosphoinositides/PIPs?
membrane lipids with head group that can be phosphorylated in different positions
help scaffold signaling proteins
what do SH3 domains bind to
proline-rich sequences
what do SH2 and PTB domains bind to
phosphorylated tyrosines
PH domains bind to
phosphoionositides (PIPs)
if a scaffold protein doesn’t require phosphorylation to bind intracellular signal proteins, what domains would it have in these binding regions?
SH3 and proline rich domains
if a scaffold protein DOES require phosphorylation to bind intracellular signal proteins, what domains would it have in these binding regions?
SH2 and PTB domains
what is a coincidence detector?
intermediate proteins that must be activated by 2 different signals, usually by 2 different kinases, to initiate further downstream signaling
