Cellular communication 3 Flashcards
What are the three downstream effectors that produce second messengers?
- adenylyl cyclase
- phospholipase C
- Phospholipase A2
Adenylyl cyclase stimulates
cAMP
Phospholipase C stimulates
IP3 and diacylglycerol
Phospholipase A2 stimulates
eicosanoids (20-carbon lipid mediators)
cAMP plays a key role in the regulation of
intracellular signal transduction
Second messenger effects are
tissue-specific
for example, cAMP may cause a response in one cell type but a completely different response in another
The intracellular effects of cAMP are mediated by the enzyme
cAMP-dependent protein kinase, PKA
IP3 is a second messenger that leads to
Ca+2 release from intracellular storage sites
Many downstream signaling events mediated by Ca+2 are modulated by a
Ca+2 sensing and binding protein, calmodulin (CaM)
What activates phospholipase C?
Gq,11 with Ca2+
Phospholipase A2 is a Ca2+ dependent enzyme that liberates _____________- from the cell membrane
arachidonic acid
What three families of lipid signaling molecules is arachidonic acid the precursor of?
prostaglandins & thromboxanes
leukotrienes
HETEs and EETs
Prostanoids, leukotrienes, HETEs, and EETs are collectively called
eicosanoids
Phosphates catalyze the removal of
phosphate groups from their substrate
Phosphorylation/dephosphorylation of a protein acts as
a molecular switch On/OFF
Binding of cAMP to the regulatory subunits causes
dissociation of the catalytic subunits
The catalytic subunits of PKA are
serine/threonine (Ser/Thr) kinases
Phosphorylation of Ser and The residues by PKA alters
protein function and cellular effects
The action of cAMP is terminated by
phosphodiesterases
the action of protein kinases is terminated by
protein phosphates
DAG and Ca2+ activate
protein kinase C
Protein kinase C is involved in many cellular functions including
receptor desensitization
modulating membrane structure events
regulating transcription
mediating immune responses
regulating cell growth
learning and memory
The action of DAG is terminated when the molecule is
recycled into new phospholipids
IP3 is a second messenger that liberates
Ca2+ from intracellular storage sites
Ca2+ signals are terminated by
ATP dependent processes:
Ca2+ is pumped out of the cell
Ca2+ is returned to the endoplasmic reticulum
The action of IP3 is terminated when the molecule is
recycled into new phospholipids
Unlike other second messengers, _____________ is NOT synthesized, liberated from a precursor molecule, or activated by enzymes
calcium
Calcium’s action is terminated by
removal from the cytoplasm by pumps and transporters to terminate its action
The active Ca2+/CAM complex has a wide range of downstream targets including
NO synthase
Ca2+/CAM-dependent protein kinases (e.g. myosin light-chain kinase)
adenylyl cyclase
cAMP-specific PDE
Which two calcium transporters are found in the plasma membrane?
the sodium-calcium exchanger (NCX)
Ca2+ ATPase (pump, PMCA)
What enzyme family catalyzes the addition of a phosphate group to a substrate?
kinases catalyze the addition of a phosphate group to their substrates
The two types of synapses in the human body are: (select 2)
a. chemical
b. thermal
c. mechanical
d. electrical
a. chemical
d. electrical
___________ play a crucial role in action potentials and other electrical behavior of membranes
Ion channels
Ion channels usually have
gated pores
An intracellular junction called ____________ helps the nervous system get the right signal to the right place in the body at the right time
the synapse
What are the two types of synapses?
electrical and chemical
_______________ are the key proteins of signal transduction at chemical synapses
Neurotransmitter receptors
Neurotransmitter receptors are transmembrane proteins that are either:
- ion channels (ionotropic receptors)
- coupled to heterotrimeric G proteins (metabotropic receptors)
Chemical synapses are
polarized (primarily one-way communication)
Chemical synapses are comprised of the
presynaptic terminal
synaptic cleft
postsynaptic membrane of the target cell
Ion channels increase the permeability of the membrane to
ions
Ion channels exhibit
ion selectivity
Ion channels usually have
gated pores
Important signals that open and close the gated pores are:
membrane voltage–> voltage-gated ion channels
chemicals–>ligand gated ion channels
pressure–> mechanically gated ion channels
Chemical signals are designed to convert _________________ into a ___________________- through the release of neurotransmitters
an electrical signal into a chemical signal
Chemical synapses communicate messages in
one direction from the presynaptic membrane to the postsynaptic membrane
Electrical synapses are designed to allow ____________ and ____________- messages to flow directly from
electrical & chemical messages to flow directly from one cell to another in a bi-directional fashion
At electrical synapses, cells are connected by
gap junctions
