communication between cells Flashcards
signal transduction pathways: explain the transmission of an extracellular signal within a cell and recall physiological examples
stages of ionotropic receptor signal transduction
ligand binds to receptor protein → change in conformation of channel protein → pore opens → pore allows ions to diffuse in or out according to conc. gradient
what is the nicotinic acetylcholine receptor involved in
muscular contraction in skeletal muscle
what is the GABAa receptor involved in
decreasing neuronal excitability in neurones
examples of secondary messengers
IP3, G-protein
how many transmembrane sections of a G-protein are there
7
what are the heterotimers of a G-protein
a, B and y
stages of G-protein linked receptor signal transduction
7-TM receptor and IC heterotrimeric G-protein (a, B and y; B and y are always bound together) are inactive → ligand binding to 7-TM changes conformation of receptor → unassociated G-protein binds to receptor as less energy required following conformational change → bound GDP molecule is exchanged for GTP, providing energy for a-subunit to dissociate from B-y-subunit → a-subunit binds to target proteins → internal GTPase activity on a-subunit dephosphorylates GTP to GDP → a-subunit dissociates from target protein, becoming inactive again, and returns to bind to B-y-subunit
diagram of G-protein linked receptor signal transduction
diagram from tissues 9
what happens to G-protein activation as long as ligand remains bound receptor
any number of G-proteins can become activated
what happens to G-protein activation once a ligand has bound
G-protein cannot be activated
3 types of G-protein linked receptor
Gs, Gi and Gq
what branch of the peripheral nervous system does the Gs protein linked receptor control
sympathetic
what does the Gs protein linked receptor stimulate and what does this do
adenyl cyclase; converts ATP to cAMP
what does cAMP do
activate protein kinase A (PKA)
example of Gs protein linked receptor and function
B1-adrenergic receptor to increase heart rate
what branch of the peripheral nervous system does the Gi protein linked receptor control
parasympathetic
what does the Gi protein linked receptor inhibit and what is the consequence
adenyl cyclase so reduces protein kinase A (PKA) levels
example of Gi protein linked receptor and function
M2-muscarinic receptor to decrease heart rate
what does Gq protein linked receptor stimulate
phospholipase C (PLC)
what does phospholipase C (PLC) do
converts PIP2 to IP3 and DAG
what does IP3 stimulate
Ca2+ release
what does DAG activate
protein kinase A (PKA)
example of Gq protein linked receptor and function
AT-1 angiotensin receptor to cause vasoconstriction
when a ligand binds to an enzyme-linked receptor, what does it cause the receptors to do
cluster
why do the receptors cluster
clustering activates enzyme activity within cytoplasmic domain
what is the enzyme activity
receptor phosphorylation
what happens when the receptors are phosphorylated
binding of signalling proteins to cytoplasmic domain
what do these signalling proteins do and what is the outcome
recruit other signalling proteins causing a signal to be generated within cell
what are enzyme-linked receptors important for
cell growth and proliferation
example of enzyme-linked receptor
tyrosine kinase
in tyrosine kinase, what is phosphorylated
tyrosine
examples of tyrosine kinase in a receptor and consequences
insulin receptor for glucose uptake; epidermal growth factor, transforming growth factor B (ErbB) for cell growth and proliferation
other enzyme-linked receptors
guanylyl-cyclase in NPRA, Ser/Thr-kinase in TBR1
what is the function of guanylyl-cyclase in NPRA
vasodilation and decrease blood pressure
what is the function of Ser/Thr-kinase in TBR1
apoptosis
types of intracellular receptors depending on location
cytoplasmic and nuclear
what are cytoplasmic intracellular receptors associated with
chaperone molecules such as heat shock proteins
stages of cytoplasmic intracellular receptor signal transduction
hormone binds to receptor → hsp dissociates → 2 hormone bound receptors form a homodimer (clustering) → homodimer translocates to nucleus → binds to DNA (very slow)
diagram of cytoplasmic intracellular receptor signal transduction
diagram from tissues 9
example of cytoplasmic intracellular receptor
glucocorticoid receptor
in the glucocotricoid receptor, what binds and what is the consequence
cortisol and corticosterone bind; decreases immune response and increases gluconeogenesis
stages of nuclear intracellular receptor signal transduction
binding of hormone ligand → transcriptional regulation
diagram of nuclear intracellular receptor signal transduction
diagram from tissues 9
example of nuclear intracellular receptor
thyroid hormone receptor
in the thyroid hormone receptor, what binds and what is the consequence
thyroxine (T4) and triiodothyronine (T3) bind; growth and development
what can detect changes in Ca2+ concentration when Ca2+ is used as a secondary messenger
proteins e.g. calmodulin, Ca2+-dependent protein kinases
4 ways of switching off an intracellular signal
receptor inactivation; receptor down-regulation (i.e. breakdown by lysosomes); production of inhibitory proteins; inactivation of intracellular signalling proteins
