Signal transduction Flashcards
Sympathetic Catecholamines
Epinephrine, norepinephrine
Parasympathetic esters
Acetylcholine
Excitatory Amino Acid Neurotransmitters
Glutamine, aspartate
Inhibitory Amino Acid Neurotransmitters
GABA, Glycine
Most common class of receptors
G-protein coupled recetors
Action of G-proteins
Pass the signal from receptor proteins to effector proteins, releasing 2nd messengers
Second messengers produced by G-protein activation
cAMP, IP3, DAG, Ion channel activity
Subunits of G-proteins
Alpha, beta, gamma
G-protein Alpha subunit
Activation alters 2nd messenger levels, can open ion channels
Family that cAMP belongs to
Adenylate Cyclase (membrane spanning enzymes)
What stimulates adenylate cyclase?
Gs-type G-proteins (and their associated receptors)
What inhibits adenylate cyclase?
Gi-type G-proteins (and associate receptors
How does cAMP exert its effect?
Activates protein kinase A (PKA)
What is PKA’s action?
Phosphorylates proteins (enzymes, pumps, channels). Can either increase or decrease activity depending on protein
Adenylate Cyclase
Family of membrane spanning enzymes (10 identified). Isoforms differ in respect to activity modulation
Kinases Activity
Phosphorylate adenylate cyclase in some cells
What protein is linked to phospholipase C activation?
Gq-mediated protein receptor
What second messengers does PLC produce?
IP3 and DAG
What is associated with PLC activation?
Ca-channel activation
Action of IP3
Binds to IP3 receptors on the ER to release the intracellular Ca stores
Action of DAG
Remains membrance associated, activates protein kinase C
Activation of PKC
Translocates from the cytosol to the membrane. PKC will phosphorylate other proteins and alter their function state
What causes IP3-mediated Ca release?
PLC
NO’s effect on cGMP levels?
Increases cGMP levels
What does guanylate cyclase do?
Forms cGMP from GTP when receptors are occiped
How is NO formed
Arginine is broken down into NO citrulline by nitric oxide synthase
What activates NO synthase?
Ca/calmodulin complex
Why is NO a unique second messenger?
it is membrane soluble
NO’s action for increasing cGMP
activates a souble, cytosolic type of guanylate cyclase (which synthisizes cGMP)
What breaks down cGMP?
Phosphodiesterases
Nicotinic receptor
Subunit form a central cavity that extends across the membrane. Ach binds to create a conformational change.
Types of nicotinic receptors found in skeletal muscle
N1 or Nm
Types of nicotinic receptors found in autonomic ganglia
N2 or Ng
Muscarinic receptor
Operate thru G-proteins to alter activity of multiple 2nd messenger systems
Muscarinic receptor that activate PLC
(the odd ones) m1, m3, m5
Muscarinic receptor that inhibit adenylate cyclase
Even ones: m2 and m4
3 families of adrenergic receptors
Beta-receptors, alph1-receptor, alpha2-receptors
What is coupled to all adrenergic receptors?
G-proteins
Beta-adrenergic receptors
Gs-mediated stimulation of adenylate cyclase
Alpha 1- adrenergic receptors
Gq- mediated PLC activation
Alpha 2-adrenergic receptors
Gi-mediated inhibition of adenylate cyclase. G0 activates K+ channels
What happens to the cell when K channels are activated?
Hyperpolarizes cells
