Synaptic cell adhesion molecules

Question 1

What are SCAMS?

Answer 1

SCAMS or Synaptic Cell Adhesion Molecules are transmembrane proteins that are localised to the synapse and interact with each other across the synapse.

Question 2

What are the functions of SCAMS?

Answer 2

They interact with each other across the synapse & contribute to synaptic plasticity

Question 3

What are examples of SCAMS

Answer 3

• Neurexin
• Neuroligings
• Ig-domain proteins – synCAMS
• Receptor phosphoserine kinases and phosphatases
• Leucine-rich repeat proteins

Question 4

What are the 4 stages of synapse formation & function?

Answer 4

1. Establishment - the pre-and postsynaptic neurons are recognized by possibly the interaction between SCAMS
2. Assembly - Recruitment of synaptic vesicles, active zones, and PSDs. SCAMS regulate physical cell-cell adhesion and serve as anchor proteins to cluster or recruit receptors or components of the synaptic signalling machinery
3. Specification - Organisation of the molecular components of the synapse which results in the functionality of the synapse
4. Plasticity - SCAMS may contribute to structural and functional synaptic plasticity in activity-dependent events.

Question 5

What are neurexins and neuroligins and what are their functions?

Answer 5

Both SCAMs and neurexins have a large alpha and short beta isoform. The alpha forms contain 6 LNS domains and 3 interspersed EGF-like domains, while beta forms contain one single LNS domain. The 6th LNS domain of the alpha neurexins and the single LNS domain of the beta neurexin bind to neuroligin to form a trans-synaptic cell adhesion complex. This complex coordinates the recruitment of calcium channels and components of the release machinery to presynaptic active zones.