Figure 1.

Regulation of Rac by PKA in neuronal cells. (A) Schematic view of the regulatory network of Rac in neuronal cells. Neuronal cells express both Dbl-family and DOCK-family GEFs. Among them, P-Rex1, STEF/Tiam2, and DOCK180 have been shown to be phosphorylated by PKA. Rac activity is required for neurite extension, migration, and so on. (B) Transgenic mice expressing FRET biosensors can be used to examine the in vivo activities of Rac1 and PKA. Embryonic intestines of E12.5 derived from transgenic mice expressing a FRET biosensor for either Rac1 or PKA were observed under two-photon microscopes. FRET images were prepared to show the activity of Rac1 and PKA. Enteric neural crest cells (ENCCs) migrate from the stomach to the colon during development. The ENCCs that migrate rapidly in chains exhibit higher Rac1 activity and lower PKA activity than the ENCCs that form a neural network.