Fig. 2.

Extracellular proteases implicated in SCN circadian system (A) and sleep-wake system (B) modulation. For the sleep-wake system, note that the figure collates data from a variety of brain regions. The strength of the data in both systems varies, from simple mRNA or protein expression through extensive functional evidence. The figure does not attempt to represent all of the cell adhesion molecules, transmitters, or interactions that are known or theorized to participate in each system, but rather aims to illustrate the potential commonalities and differences between the systems.