Figure 7. Model illustrating flexible RPTPσ ectodomain sampling of extracellular ligands.

(a) At the growth cone, RPTPσ interacts with cell surface and basal membrane proteoglycans to mediate axonal extension. (b) Upon contact with target cells, to shift to the role of synaptic organizer, RPTPσ adopts elongated conformations to protrude from the presynaptic proteoglycan haze and bind postsynaptic ligands such as TrkC and NGL-3. Subsequent independent or coordinated interactions with additional synaptic ligands are shown. Red boxes (left hand panels) indicate growth cone (a) or synapse (b) regions that are illustrated in the right-hand cartoons.