Making neural connections 2 Flashcards
What do cell adhesion molecules (CAMs) do?
Sit in cell membrane and bind molecules in membranes of neighbouring cells
Sit in cell membrane and bind molecules in the extracellular matrix
Localised to specific junctions and bind proteins in similar junctions on neighbouring cells
Links to cytoskeleton + secondary messenger signalling pathways affecting cell behaviour
CAMs examples?
Cadherins, integrins
Key molecule for adhesion to the extracellular matrix?
Integrins
What are cadherins?
Calcium-dependent, transmembrane, homophilic, act as dimers, major component of adherens junctions.
How do cadherins link to the atin cytoskeleton?
via catenins
What effect can cadherins have on the cytoskeleton?
Stabilise it
How do Ig-CAMs work?
Interaction between IGG domains
The domain bind to equivalent domains in the partner proteins, mediates their adhesion
Which molecule are Ig-CAM similar to?
IgGs
Examples of Ig-CAM interactions?
NCAM-NCAM (neuroCAM)
Neurofascin-CASPR1
What happens after Ig-CAMs interact?
Change in conformation which signals to the intracellular C terminus
What does the intracellular C terminus of the Ig-CAMs do?
Links to the actin cytoskeleton
What are integrins?
Transmembrane proteins, bind adhesive glycoproteins e.g. fibronectin, in the extracellular matrix (ECM).
Structure of integrins?
Alpha Beta dimers
How do integins recognise ECM proteins?
Recognise an arginine-glycine-aspartate sequence in ECM proteins
Examples of ECM proteins that integrin can recognise?
vitronectin, fibronectin, laminin.
What is integrin binding dependent on?
Calcium
WHat does integrin link to intracellularly?
Beta subunit links to actin cytoskeleton
Four guidance mechanisms in axon pathfinding?
Chemoattraction, chemorepulsion, contact attraction, contact repulsion
Secreted ligands for axon pathfinding?
Chemoattraction, chemorepulsion
Membrane bound ligands for axon pathfinding?
contact attraction, contact repulsion
How is the strength of response changes if the gradient of the secreted ligands is across the growth cone?
The strength of response is diff on diff sides–> if the gradient is coming from one side and is repulsive then that side will move away more than the other side, causing it to turn
How does contact repulsion/adhesion work?
They form “channels/pathways” (i.e. either side is repulsion and in the middle is adhesion) to direct the growth cone as to where to go
Four types of guidance molecules?
Semaphorins, Netrins, Slits, Ephrins
What are pioneer axons?
Axons that travel ahead and read the environmental signals present
What do secondary axons do?
Fasiculation
What is fasiculation?
follow an axon and adhere to it
How do axons adhere to one another?
NCAMS, and some more specific contact mediated guidance cues
What is defasicualtion?
some axons in the bundles split off and go to different areas of the body
WHen does defasciculation happen?
When contact mediated guidance cues between axons become repellant
