title: Role of LKB1-SAD/MARK pathway in neuronal polarization.
abstract: The formation of axon/dendrite polarity is critical for the neuron to perform its signaling function in the brain. Recent advance in our understanding of cellular and molecular mechanisms underlying the development and maintenance of neuronal polarity has been greatly facilitated by the use of the culture system of dissociated hippocampal neurons. Among many polarization-related proteins, we here focus on the mammalian LKB1, the counterpart of the C. elegans Par-4, which is an upstream regulator among six Par (partitioning-defective) genes that act as master regulators of cell polarity in different cell types across evolutionary distant species. Recent studies have identified LKB1 and its downstream targets SAD/MARK kinases (mammalian homologs of Par-1) as key regulators of neuronal polarization and axon development in cultured neurons and in developing cortical neurons in vivo. We will review the properties of and interactions among proteins in this LKB1-SAD/MARK pathway, drawing upon information obtained from both neuronal and non-neuronal systems. Due to central role of the protein kinase A-dependent phosphorylation of LKB1 in the activation of this pathway, we will review recent findings on how cAMP and cGMP signaling may serve as antagonistic second messengers for axon/dendrite development, and how these cyclic nucleotides may mediate the action of extracellular polarizing factors by modulating the activity of the LKB1-SAD/MARK pathway.
authors.affiliation: Department of Neurobiology and Behavior, State University of New York, Stony Brook, NY 11794-5230, USA. maya.shelly@stonybrook.edu
authors.forename: Maya
authors.initials: M
authors.lastname: Shelly
authors.forename: Mu-Ming
authors.initials: MM
authors.lastname: Poo
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000502:physiology*; D006801:Humans; D009474:Neurons / Q000201:enzymology* / Q000648:ultrastructure; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D017346:Protein Serine-Threonine Kinases