Enzyme-Linked Receptors

Enzyme-Linked Receptors

1. Characteristics

   • Often exist as inactive monomers
   • Ligand binding induces activation by di/trimerisation
   • the monomers transphosphorylate each other
   • adaptor proteins recognise change in structure

2. Transforming Growth Factor Beta (A Ligand)

   • brings the monomers together (that exist seperatly)
     • Heterodimerisation occurs (the monomers are not idetical)
       • Phosphorylation occurs on the serine-threonine residues
         • This ultimately activates the TGF receptor

3. Nerve Growth Factor (NGF) (A Ligand)

   • NGF presence causes homodimerisation of receptors with intrinsic cytosolic tyrosine kinase activity
     • Phosphorylation occurs on the tyrosine residues
     • note here, that the monomers are identical

4. Cytokines

   • Heterodimerisation of receptors...
     • whose cytosolic domains are associated with seperate non-tyrosine kinases

5. Receptor Tyrosine Kinase Signalling

   • Trk Receptors = Tropomyosin-related Kinases
     • The receptor for NGF is TrkA
     • The receptor for BDNF (brain-derived neurotrophic factor) is TrkB
     • The receptor for NT3 (Neurotrophin-3) is Trk C
     • The receptor for NT4/5 is Trk B