University of Vermont COBRE (P20 RR016435)
"Center for Neuroscience Excellence"

Pilot Project 1: "Spatial Regulation of Protein Kinase A Signaling During Growth Cone Guidance"
Investigator: Alan Howe, Ph.D.

The protrusion, movement and guidance of neuronal growth cones are driven by actin cytoskeletal dynamics that respond to attractive or repulsive guidance cues. Importantly, the balance between growth cone attraction and repulsion is modulated by cAMP and the cAMP-dependent protein kinase (PKA). Recent results from our laboratory have shown that PKA presides over the chemotactic migration of fibroblasts in a most intriguing way. Specifically, a subset of PKA regulatory subunits, as well as PKA activity, and the phosphorylation of a number of cytoskeletal targets are all significantly enriched in protruding pseudopodia and lamellipodia. Moreover, both inhibition of PKA activity and inhibition of PKA interaction with AKAPs (A-kinase anchoring proteins) prevent pseudopod formation and inhibit chemotaxis. This suggests that the formation of protrusive structures during cell movement requires not only PKA activity, but the specific localization of PKA activity. Although AKAP-mediated PKA localization has been shown to be important for some aspects of neuronal function, and despite the central importance of PKA signaling for regulating growth cone guidance, there is little to no information regarding the role of spatial regulation of PKA in neurite outgrowth and growth cone motility. Therefore, we propose to determine whether PKA is spatially regulated during neurite outgrowth and to investigate whether AKAP-mediated localization of PKA is required for efficient neurite outgrowth and axon guidance. For these studies, a compliment of microscopy of fixed and live cells and biochemical fractionation of growth cones and axon hillocks will provide detailed information on the dynamic distribution of PKA subunits and activity within protrusive neuronal processes. These efforts will provide important preliminary data that may implicate spatial regulation of PKA activity as an important and heretofore uninvestigated facet of growth cone guidance.