Cell Signalling

Cell Signalling

1. types of cell signalling

   • Autocrine
     • signalling molecules bind to the receptors of the cell releasing the signalling molecules. - cell to same cell
     • an example is the regulation of somatostatin secretion in the stomach
   • Paracrine
     • signalling molecules bind to receptors on adjacent cells. - they do not travel through the circulatory system.
     • an example is the action of histamine in the stomach
   • endocrine
     • signalling from one cell to another (which is further away). signalling molecules have to bind to carrier molecules and travel through the circulatory system.
     • an example is the hypophyseal portal system

2. receptors

   • nuclear receptors
     • occurs in hours
     • gene transcription -> protein synthesis -> cellular effects
     • example: oestrogen receptors
   • ligand gated ion channels
     • occurs in milliseconds
     • ions -> hyperpolarisation or depolarisation -> cellular effects
     • examples are; Nicotinic and Ach receptor
       • nicotinic acetylcholine receptors are permeable to Na+, K+ and Ca+. They are non-specific cation channels. And modulate fast synaptic excitations
   • kinase-linked receptors
     • occurs in hours
     • protein phosphorylation -> gene transcription -> protein synthesis -> cellular effects
     • example; cytokine receptor
   • G-protein coupled receptors
     • occurs in seconds
     • signalling molecule binds to receptor. receptor changes conformation which the turns GDP to GTP. GTP binds to G alpha S which then binds to AC. AC turns ATP to cAMP and then cAMP to PKA. This inhibits MLCK activity.
     • Examples are; Muscarinic and Ach receptor