Non-muscle myosin II regulates neuronal actin dynamics by interacting with guanine nucleotide exchange factors

• Published in: PloS one 2014-04, Vol.9 (4), p.e95212
• Main Authors: Shin, Eun-Young, Lee, Chan-Soo, Yun, Cheong-Yong, Won, So-Yoon, Kim, Hyong-Kyu, Lee, Yong Hee, Kwak, Sahng-June, Kim, Eung-Gook
• Format: Article
• Language: English
• Subjects: Aberration; Actin; Actins - metabolism; Activation; Animals; Axonogenesis; Axons; Axons - drug effects; Axons - metabolism; Biochemistry; Biology and life sciences; Brain research; cdc42 GTP-Binding Protein - metabolism; Cdc42 protein; Cell adhesion & migration; Cells, Cultured; Cloning; Cones; Deactivation; Differentiation; Dissociation; Female; Fibroblasts; Fluorescence resonance energy transfer; Growth cones; Growth Cones - drug effects; Growth Cones - metabolism; Guanine; Guanine nucleotide exchange factor; Guanosine triphosphatases; Guanosinetriphosphatase; Heterocyclic Compounds, 4 or More Rings - pharmacology; Hippocampus; Hippocampus - cytology; Inactivation; Intersectin; Ischemia; Kinetics; Localization; Medical research; Medicine; Models, Biological; Motility; Muscle proteins; Muscles; Myosin; Nerve growth factor; Nerve Growth Factors - metabolism; Neurites - drug effects; Neurites - metabolism; Neurons - drug effects; Neurons - metabolism; Nonmuscle Myosin Type IIB - metabolism; p21-Activated Kinases - metabolism; Physiological aspects; Protein Binding - drug effects; Protein Structure, Tertiary; Pseudopodia - drug effects; Pseudopodia - metabolism; rac1 GTP-Binding Protein - metabolism; Rac1 protein; Rats, Sprague-Dawley; Rho Guanine Nucleotide Exchange Factors - chemistry; Rho Guanine Nucleotide Exchange Factors - metabolism; Signal transduction; Signal Transduction - drug effects; Signaling; siRNA; Tiam1 protein
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0095212

Non-muscle myosin II (NM II) regulates a wide range of cellular functions, including neuronal differentiation, which requires precise spatio-temporal activation of Rho GTPases. The molecular mechanism underlying the NM II-mediated activation of Rho GTPases is poorly understood. The present study explored the possibility that NM II regulates neuronal differentiation, particularly morphological changes in growth cones and the distal axon, through guanine nucleotide exchange factors (GEFs) of the Dbl family. NM II colocalized with GEFs, such as βPIX, kalirin and intersectin, in growth cones. Inactivation of NM II by blebbistatin (BBS) led to the increased formation of short and thick filopodial actin structures at the periphery of growth cones. In line with these observations, FRET analysis revealed enhanced Cdc42 activity in BBS-treated growth cones. BBS treatment also induced aberrant targeting of various GEFs to the distal axon where GEFs were seldom observed under physiological conditions. As a result, numerous protrusions and branches were generated on the shaft of the distal axon. The disruption of the NM II-GEF interactions by overexpression of the DH domains of βPIX or Tiam1, or by βPIX depletion with specific siRNAs inhibited growth cone formation and induced slender axons concomitant with multiple branches in cultured hippocampal neurons. Finally, stimulation with nerve growth factor induced transient dissociation of the NM II-GEF complex, which was closely correlated with the kinetics of Cdc42 and Rac1 activation. Our results suggest that NM II maintains proper morphology of neuronal growth cones and the distal axon by regulating actin dynamics through the GEF-Rho GTPase signaling pathway.