Lecture 5 - Membrane signalling overview

Question 1

Membrane as barriers

Answer 1

• Need transduction mechanisms (receptors: in contact with both external and internal environment)
• Allows selectivity in responses
• Exploitation of Barrier
• Ca²⁺ signalling, LGICs – exploit impermeability of membranes to generate transient signals

Question 2

Signal organisation

Answer 2

• Membranes keep receptors and signalling proteins with lipid anchors concentrated, and restrict movement to 2 dimensions
• Useful surfaces for the assembly of signalling complexes – dynamic recruitment (protein-protein or protein-lipid interaction)
• Sequestration of signalling molecules in the absence of a stimulus

Question 3

Membrane fluidity

Answer 3

• Mobility of membrane proteins allows interaction with other signalling molecules:
  RTK monomers; GPCRs, G-proteins, small GTPases, GRKs.

Question 4

Signalling intermediates

Answer 4

• Lipids act as signalling molecules
• Lipids act as precursors of second messengers
• Membrane-localised signalling enzymes

Question 5

Signal termination

Answer 5

Role of membrane proteins (or proteins recruited to the membrane) in signal inactivation: ion pumps, enzymes, GAPs

Internalisation (endocytosis) of receptors