This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.During development, extracellular guidance cues regulate actin cytoskeletal dynamics in neuronal growth cones to control axon outgrowth and trajectory towards proper synaptic targets. Among these cues are the netrins, a family of secreted molecules capable of chemoattraction, chemorepulsion, and regulation of branching behavior. The response to netrin signaling is mediated principally through the DCC (Deleted in Colorectal Cancers) receptor family. Delineation of the signals downstream of DCC and the mechanisms through which they couple to cytoskeletal dynamics is fundamentally important to our understanding of netrin-mediated developmental events. We have previously shown that the cAMP-dependent protein kinase (PKA) is spatially regulated during chemotactic cell movement and that subcellular anchoring of PKA is required for efficient chemotaxis. Our preliminary data show that expression of DCC promotes activation of PKA in a ligand-dependent fashion. This activity correlates with phosphorylation of the Mena/VASP family of cytoskeletal regulators, an effect abrogated by disruption of PKA anchoring, suggesting the involvement of a specific PKA-containing signaling complex. We have also observed that co-immunoprecipitation of PKA and DCC is disrupted by inhibition of PKA anchoring. These data support a hypothesis in which association with, and activation of, PKA by DCC is involved in coupling netrin/DCC signaling to cytoskeletal regulation during axon guidance. We will test this by (1) elucidating the nature of the interaction between DCC and PKA, (2) investigating the molecular consequences of DCC association with and signaling through PKA, and (3) investigating the functional consequences of DCC/PKA signaling on neuronal morphology, dynamics, and guidance.
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