Cell Signaling Part 1 Flashcards
process of converting one type of signal to another type
signal transduction
4 types of ways in which cells signal
- endocrine
- paracrine
- synaptic
- contact-dependent
hormone produced in endocrine glands are secreted into the bloodstream and are distributed widely throughout the body
endocrine
paracrine signals are released by cells into the ECF in their neighborhood and act locally
paracrine
neuronal signals are transmitted electrically along a nerve cell axon. when this electrical signal reaches the nerve terminal, it causes the release of neurotransmitters onto adjacent target cells.
synaptic
a cell-surface-bound signal molecule binds to a receptor protein on a adjacent cell.
contact dependent
complexity of receptors is amplified due to
- 1000 of individual receptors within a family
- multiple transducers
- second messengers
if a cell is deprived of survival signals most cells undergo
suicide (apoptosis)
multiple extracellular signals can produce what different outcomes?
- survive
- grow and divide
- differentiate
- suicide
which cell processes of EC signals occur faster
metabolic, secretion, altered protein function (non gene expression)
which cell processes of EC signals occur slowest
gene expression and protein synthesis
extracellular signal molecules generally fall into two classes —-
- (largest) too large/too hydrophilic require a receptor protein
2 (smaller) hydrophobic
steroid hormones rely on
intracellular receptor proteins (hydrophobic)
when activated by hormone binding, they act as transcription regulators in the nucleus
nuclear receptor
3 key steps in cell signaling
- reception
- transduction
- response
intracellular signaling molecules can (4 steps)
- relay
- amplify
- integrate
- distribute
mechanism where a signaling pathway can regulate itself
feedback regulation
two types of protein switches
- protein phosphorylation
2. gtp-binding proteins
turn on of protein phosphorylation
protein kinase (ATP-ADP) adds the phosphate group
turn off of protein phosphorylation
protein phosphatase (removing a phosphate)
two main groups of kinases
serine/threonine kinases and tyrosine kinases
activated when GDP is exchanged for GTP
GTP binding protein
protein then switched itself off by
GTP hydrolysis
the activity of monomeric gtp-binding proteins is controlled by
GEF and GAPS
promote the exchange of GDP for GTP “on”
GEF (guanine exchange factors)
stimulate the hydrolysis of GTP to GDP “off”
GAPS (GTPase activating proteins)
3 main classes of cell-surface receptors
- ion channel coupled
- g protein could
- enzyme coupled
Change the permeability of the plasma membrane to selected ion, produce and electrical current
ion channel coupled receptors
Activate membrane bound trimeric GTP-binding proteins that in turn activate an enzyme or an ion channel in the cell membrane that then initiates a signaling cascade
g-protein coupled receptors
Act as enzymes or associate with enzymes inside the cell, which in turn activate a signaling cascade
enzyme-coupled
Polypeptide transverses the membrane as seven alpha helixes
GPCRs
all g proteins have what type of subunits
alpha, beta, and gamma
How long activation lasts depends on
GTPase activity in the alpha subunit
g proteins can activate what type of channels
ion
Ach activates what g protein
Gi
beta gamma complex opens which channel
K+ (slows heart rate)
closes the channel
hydrolysis in GTP
intracellular signaling molecules
second messengers
- Small molecules that carry signals into a cell or signal locally within a cell
- Chemically diverse – include inorganic ions, lipids, gases, and nucleotides
second messengers
4 types of second messengers
- cyclic nucleotides
- lipids
- calcium
- nitric oxide
Used for transferring into cells the effects of hormones like glucogen and adrenaline, which themselves do not enter the cell
binds and regulates the function of ion channels and can be involved in immune inflammatory responses
cAMP
two types of cyclic nucleotides
cAMP and cGMP
cAMP is formed from ____, that removes ____ phosphate groups, allowing the remaining one to join back on the AMP molecule
ATP, two,
removal of two phosphates to make the cyclic AMP is catalyzed by what?
adenylyl cyclase
can inactivate cAMP
cyclic AMP phosphodiesterase
adrenaline signaling uses what type of protein binding
G-protein
arenaline signaling process
adrenaline binds to G-protein, which activates cAMP, which activates PKA, which results in rapid breakdown of glycogen
activation of PKA in an adrenaline response can also activate
downstream gene transcription
Phospholipase C =
Gq
Phospholipase C actives 2 signaling pathways
- IP3 and DAG
some cell responses mediated by phospholipase C activation
- vasopression—-liver—glycogen breakdown
- Ach—- pancreas—- sec of amylase
- Ach—– smooth muscle—-contraction
- thrombin—–blood platelets—-aggregation
three parent lipids that give rise to most lipid 2nd messengers
- PIP2
- PC
- Spingolmyelin
translocates from the cytosol to the plasma membrane
can regulate gene expression, cell motility, generation of 2nd messengers
PKC
It is the only second messenger that is controlled by release into and removal from the cytosol. All other are synthesized and metabolized
Calcium
calcium controls what 4 things
synaptic transmission
fertilization
secretion
muscle contraction
calcium + calmodulin actives
CaM-kinases
when CAM kinases are activates calmodulin will
wrap around its target protein to activate it
diffuses through cytosol and binds to ER to open calcium channels
IP3
takes calcium ions and adheres to activate PKC
DAG
