title: Kalirin-9 and Kalirin-12 Play Essential Roles in Dendritic Outgrowth and Branching.
abstract: Proteins derived from the Kalrn gene, encoding 2 Rho guanine nucleotide exchange factor (GEF) domains, affect dendritic and axonal morphogenesis. The roles of endogenous Kalirin-9 (Kal9) and Kalirin-12 (Kal12), the Kalrn isoforms expressed before synaptogenesis, have not been studied in neurite growth and maturation during early development. The Caenorhabditis elegans and Drosophila melanogaster orthologues of Kalrn encode proteins equivalent to Kal9 but, lacking a kinase domain, neither organism expresses a protein equivalent to Kal12. Both in vivo and in vitro analyses of cortical neurons from total Kalrn knockout mice, lacking all major Kalirin isoforms, revealed a simplified dendritic arbor and reduced neurite length. Using isoform-specific shRNAs to reduce Kal9 or Kal12 expression in hippocampal cultures resulted in stunted dendritic outgrowth and branching in vitro, without affecting axonal polarity. Exposing hippocampal cultures to inhibitors of the first GEF domain of Kalirin (ITX3, Z62954982) blunted neurite outgrowth and branching, confirming its essential role, without altering the morphology of neurons not expressing Kalrn. In addition, exogenous expression of the active kinase domain unique to Kal12 increased neurite number and length, whereas that of the inactive kinase domain decreased neurite growth. Our results demonstrate that both endogenous Kal9 and endogenous Kal12 contribute to dendritic maturation in early development.
authors.affiliation: Department of Neuroscience, UConn Health, Farmington, CT 06030, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Neuroscience, UConn Health, Farmington, CT 06030, USA Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030, USA.
authors.forename: Betty A
authors.initials: BA
authors.lastname: Eipper
authors.affiliation: Department of Neuroscience, UConn Health, Farmington, CT 06030, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Mains
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000196:embryology* / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016501:Neurites / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D020662:Guanine Nucleotide Exchange Factors; C102365:Kalrn protein, rat; D010750:Phosphoproteins; D020033:Protein Isoforms; D000251:Adenosine Triphosphatases; C115505:Hgs protein, rat; C499134:Rac1 protein, rat; D020830:rac1 GTP-Binding Protein
keywords: Kalirin knockout mouse; Rho GEF; kinase; neurite