19/10/18
Dr Tania Maffucci
Types of Receptors and Signal Regulation
Receptors Found in Membrane
1. Ligand Gated Ion Channels
• Channels need to be activated by ligands to open
• This then allows the ion to pass through
o E.g. GABA receptor in nervous system allows Cl- through when GABA site is full
2. Enzyme Linked Receptors
• Ligand binds to ligand binding domain – LBD
• Enzyme intracellular side of receptor
o This enzyme activates 2nd messenger
• Examples:
o Guanyl cyclase
▪ Receptor converts GTP to cGMP
▪ cGMP activates cascade of kinases e.g. PKG
▪ Relaxes smooth muscle, regulates
apoptosis
o Transforming growth factor β
▪ Involved in proliferation, chemotaxis and
differentiation
▪ Growth factor binds, and enzyme
phosphorylated
▪ Enters nucleus and affects transcription
of mRNA
o Serine/Threonine kinases
▪ Enzyme from receptor phosphorylates
either protein and these go on to affect cell
o Tyrosine kinase
▪ Kinase enzyme is on receptor but this one only phosphorylates tyrosine
▪ Used for receptors like insulin, PI3K/Akt cascade and growth factors
▪ Very common
▪ Some receptors dimerise after ligand binding then phosphorylate each other
• But some receptors autophosphorylate
o MAPK cascade
▪ Ras activates cascade of mitogen activated protein kinases (MAPKs)
▪ MAPKs activate proteins in the cell
Dr Tania Maffucci
Types of Receptors and Signal Regulation
Receptors Found in Membrane
1. Ligand Gated Ion Channels
• Channels need to be activated by ligands to open
• This then allows the ion to pass through
o E.g. GABA receptor in nervous system allows Cl- through when GABA site is full
2. Enzyme Linked Receptors
• Ligand binds to ligand binding domain – LBD
• Enzyme intracellular side of receptor
o This enzyme activates 2nd messenger
• Examples:
o Guanyl cyclase
▪ Receptor converts GTP to cGMP
▪ cGMP activates cascade of kinases e.g. PKG
▪ Relaxes smooth muscle, regulates
apoptosis
o Transforming growth factor β
▪ Involved in proliferation, chemotaxis and
differentiation
▪ Growth factor binds, and enzyme
phosphorylated
▪ Enters nucleus and affects transcription
of mRNA
o Serine/Threonine kinases
▪ Enzyme from receptor phosphorylates
either protein and these go on to affect cell
o Tyrosine kinase
▪ Kinase enzyme is on receptor but this one only phosphorylates tyrosine
▪ Used for receptors like insulin, PI3K/Akt cascade and growth factors
▪ Very common
▪ Some receptors dimerise after ligand binding then phosphorylate each other
• But some receptors autophosphorylate
o MAPK cascade
▪ Ras activates cascade of mitogen activated protein kinases (MAPKs)
▪ MAPKs activate proteins in the cell
