title: Stabilization of actin bundles by a dynamin 1/cortactin ring complex is necessary for growth cone filopodia.
abstract: Dynamin GTPase, a key molecule in endocytosis, mechanically severs the invaginated membrane upon GTP hydrolysis. Dynamin functions also in regulating actin cytoskeleton, but the mechanisms are yet to be defined. Here we show that dynamin 1, a neuronal isoform of dynamin, and cortactin form ring complexes, which twine around F-actin bundles and stabilize them. By negative-staining EM, dynamin 1-cortactin complexes appeared as "open" or "closed" rings depending on guanine nucleotide conditions. By pyrene actin assembly assay, dynamin 1 stimulated actin assembly in mouse brain cytosol. In vitro incubation of F-actin with both dynamin 1 and cortactin led to the formation of long and thick actin bundles, on which dynamin 1 and cortactin were periodically colocalized in puncta. A depolymerization assay revealed that dynamin 1 and cortactin increased the stability of actin bundles, most prominently in the presence of GTP. In rat cortical neurons and human neuroblastoma cell line, SH-SY5Y, both dynamin 1 and cortactin localized on actin filaments and the bundles at growth cone filopodia as revealed by immunoelectron microscopy. In SH-SY5Y cell, acute inhibition of dynamin 1 by application of dynamin inhibitor led to growth cone collapse. Cortactin knockdown also reduced growth cone filopodia. Together, our results strongly suggest that dynamin 1 and cortactin ring complex mechanically stabilizes F-actin bundles in growth cone filopodia. Thus, the GTPase-dependent mechanochemical enzyme property of dynamin is commonly used both in endocytosis and regulation of F-actin bundles by a dynamin 1-cortactin complex.
authors: Department of Neuroscience, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan.
authors: Hiroshi
authors: H
authors: Yamada
authors: Tadashi
authors: T
authors: Abe
authors: Ayano
authors: A
authors: Satoh
authors: Nana
authors: N
authors: Okazaki
authors: Shota
authors: S
authors: Tago
authors: Kinue
authors: K
authors: Kobayashi
authors: Yumi
authors: Y
authors: Yoshida
authors: Yoshiya
authors: Y
authors: Oda
authors: Masami
authors: M
authors: Watanabe
authors: Kazuhito
authors: K
authors: Tomizawa
authors: Hideki
authors: H
authors: Matsui
authors: Kohji
authors: K
authors: Takei
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000494:pharmacology; D001921:Brain / Q000166:cytology; D002478:Cells, Cultured; D051356:Cortactin / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D003600:Cytosol / Q000378:metabolism; D034284:Dynamin I / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D009154:Mutation / Q000502:physiology; D009447:Neuroblastoma / Q000473:pathology; D009474:Neurons / Q000166:cytology* / Q000648:ultrastructure; D011485:Protein Binding / Q000502:physiology; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014162:Transfection
chemical_list: D000199:Actins; D000906:Antibodies; D051356:Cortactin; C495869:Cttn protein, mouse; D006835:Hydrazones; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000255:Adenosine Triphosphate; D034284:Dynamin I; D020558:GTP Phosphohydrolases