DR Medhat MRCP

Disease
Signal
transduction
Ligands
(1 st messenger)
Classes
Ligand-gated ion
channels
(= ionotropic receptors)
o Open in response to
ligand to allow passage
of ions (e.g Na,K,Ca,..)
Transmitters :
- Nicotinic A.ch
- GABA-A
- Glutamate
Mediate fast responses
e.g
1) Neurotransmission
2) Muscle contraction
Classification of target cell receptors
Membrane-bound receptors
G-protein coupled
receptors
o They sense ligand
outside the cell & ++
intracellular signal
transduction pathways
Transmitters :
- Muscarenic A.ch
- GABA-B
- Adrenaline, noradrenaline
- Dopamine
Hormones (see below)
2G in flat camp→cAMP
GTAG→IP3 pathway
Mediate slow responses
via :
1) cAMP pathway.
2) Inositol triphosphate
(IP3) pathway.
Receptors with integral (intrinsic) enzymatic
function
Tyrosine kinase
receptors
Growth factor (GH)
(mainly)
Insulin
Interferon
Prolactin
Oxytocin
Erythropoietin
Ligand-receptor
binding dimerisation
of receptor & ++ of
intrinsic tyrosine kinase
activity.
Guanylate cyclase
receptors
Atrial natriuretic peptide
(ANP).
Nitric oxide (NO)
Intracellular
(cytosolic)
receptors
Lipid-soluble
hormones e.g steroid
hormones
(VET CAP)
Lipophilic ligands
- Vit D
- Estrogen
- Testosterone
- Cortisol
- Aldosterone
- Progesterone.
cGMP pathway ligand-receptor
complex goes to
nucleus→ ++
gene
transcription
e.g ++ NMDA
glutamate receptors
allows Ca 2+ entry
++ apoptosis &
neurotoxicity .e.g
(Alzhiemer, parkinson)
Cholera ++ GP-CR in
enterocytes ++
adenylate cyclase
cAMP Nacl
(+H2O) efflux into stool
سؤال diarrhea. watery
Mutation in RET gene
on chromosome 10
that encodes for
protein of tyrosine
kinase receptors
overactive R MEN II
Mutation in RETGC-1 gene
that encodes for guanylate
cyclase photo-receptors in
cons of retina disturbing
of phototransduction
process (con dystrophy)