L1 - Overview of cell signalling

• Cell to cell communication is also called cell signalling
• Cell Signalling/Intercellular Communication → signal send message to target cell

  1. Synthesis of signal molecule
  2. Release of signal molecule
  3. Transport of signal molecule to target detection of signal (reception) by target cell
  4. Response by target cell
  5. Some form of feedback - (that) signal has been received
• Water Soluble:

  • Stored in lipid vesicle
  • Allow rapid release via exocytosis
  • Travel freely in blood
  • Can't enter cell (phospholipid bilayer)
  • Message transduced via cell surface receptor
  • eg neurotransmitters, peptides
• Lipid Soluble:

  • Can't be stored as leaks across membrane
  • Made on demand (slow response)
  • Travels in blood with a carrier protein
  • not chemically compatible (blood = water environment)
  • Can enter target cells by crossing membrane
  • Acts on intracellular receptors often to directly regulate gene expression
  • eg steroid, testosterone
• Juxtacrine via gap junctions (via direct cell to cell contact)

  • Specificity = by direct contact
  • specific receptor for specific signal

  or

  • Specificity by receptor expression & direct contact
  • eg notch pathway
  • For more complex info
• Autocrine via nearby cells of same type

  • Specificity by selective receptor expression & rapid degradation of signal molecule
• Paracrine = local signalling between different cell types

  • Specificity by selective receptor expression & rapid degradation of signal molecule
• Endocrine = hormones carried in the blood

  • Specificity selective receptor expression
• Neuronal = neurotransmitter released from neurons are localised synaptic sites

  • Specificity by precise contacts & rapid removal of neurotransmitter to prevent diffusion
• Neuroendocrine = from neurons in to blood