signal transduction Flashcards
Dr Danny Zisterer
Communication by extracellular signals(so racist that David thought racist thoughts)
Synthesis
* Release of signalling molecule by signalling cell
* Transport of signal to target cell
* Detection of signal by specific receptor protein
* Transduction of signal (e.g. using second messengers)
* Response: change in cellular metabolism, function or
development triggered by receptor:signal complex
* Termination of signal
name the four types of cell surface receptors
G-protein coupled receptors (GPCR),
Ion-channel receptors,
Tyrosine kinase-linked receptors,
Receptors with intrinsic enzymatic activity.
example of g protein receptors
epinephrine
example of Ion-channel receptors
acetylcholine
example of Tyrosine kinase-linked receptors
erythropoietin
Receptors with intrinsic enzymatic activity
insulin
Lipophilic hormones with intracellular receptors
steroid hormones, thyroxine, Vitamin D
Lipophilic hormones with cell-surface receptors
prostaglandins
Hydrophilic hormones with cell surface receptors
Peptide hormones e.g. insulin and glucagon
Small charged molecules e.g. epinephrine and histamine
An example of a Signal Transduction Pathways
epinephrine+beta adergentic receptor = energy store mobalistaion
Common second messengers
cAMP, IP3, Calcium ion
what is the problem associated with secondary messengers?
Use of common second messengers in multiple
signalling pathways creates both opportunities (cross
talk) and potential problems
Protein phosphorylation is a common means of
information transfer but how? ie name the enzyme.
Specific enzymes, known as protein kinases
phosphorylate target proteins. ATP is the most common donor
what do protein kinases do?
transfer phosphoryl groups from ATP to specific serine, threonine
and tyrosine residues on specific proteins
what removes the phosphate groups hydrolytically?
Protein phosphatases
*Phosphorylation and dephosphorylation reactions are not
the reverse of one another.Why is this so?
Each is essentially irreversible
under physiological conditions.
Indeed a phosphate group does what?
A phosphate group adds two negative charges to the
protein-allows new electrostatic interactions to be formed. A phosphate group can allow for three hydrogen binds to be formed.
what is amplification?
when enzymes activate enzymes, the number of affected molecules increases geometrically in an enzyme cascade.
Cyclic AMP activates protein kinase A (PKA)
by what?
altering the quaternary structure
g-protein receptors look like what?
contains seven helices that
span the membrane bilayer
how are G-Protiens activated by ligands?
Cytoplasmic loops and C-termini change
conformation in response to ligand
binding
name some of the Biological Functions Mediated by
GPCR or 7TM Receptor
Smell
Taste
Neurotransmission
Hormone Action
Hormone Secretion
Control of Blood Pressure
Embryogenesis
Development
Vision
Viral Infection
what was the first cellular g-protein receptor identified
Rhodopsin: takes part in visual signal
transduction
GCPR are the sites for what?
Target of almost half of all modern pharmaceutical
drugs (e.g. beta-blockers, anti-histamines and
various psychiatric drugs)