title: ACAP3 regulates neurite outgrowth through its GAP activity specific to Arf6 in mouse hippocampal neurons.
abstract: ACAP3 (ArfGAP with coiled-coil, ankyrin repeat and pleckstrin homology domains 3) belongs to the ACAP family of GAPs (GTPase-activating proteins) for the small GTPase Arf (ADP-ribosylation factor). However, its specificity to Arf isoforms and physiological functions remain unclear. In the present study, we demonstrate that ACAP3 plays an important role in neurite outgrowth of mouse hippocampal neurons through its GAP activity specific to Arf6. In primary cultured mouse hippocampal neurons, knockdown of ACAP3 abrogated neurite outgrowth, which was rescued by ectopically expressed wild-type ACAP3, but not by its GAP activity-deficient mutant. Ectopically expressed ACAP3 in HEK (human embryonic kidney)-293T cells showed the GAP activity specific to Arf6. In support of this observation, the level of GTP-bound Arf6 was significantly increased by knockdown of ACAP3 in hippocampal neurons. In addition, knockdown and knockout of Arf6 in mouse hippocampal neurons suppressed neurite outgrowth. These results demonstrate that ACAP3 positively regulates neurite outgrowth through its GAP activity specific to Arf6. Furthermore, neurite outgrowth suppressed by ACAP3 knockdown was rescued by expression of a fast cycle mutant of Arf6 that spontaneously exchanges guanine nucleotides on Arf6, but not by that of wild-type, GTP- or GDP-locked mutant Arf6. Thus cycling between active and inactive forms of Arf6, which is precisely regulated by ACAP3 in concert with a guanine-nucleotide-exchange factor(s), seems to be required for neurite outgrowth of hippocampal neurons.
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan School of Integrative and Global Majors, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miura
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Tsunaki
authors.initials: T
authors.lastname: Hongu
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamauchi
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Funakoshi
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Katagiri
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Ohbayashi
authors.affiliation: Department of Physiological Chemistry, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan ykanaho@md.tsukuba.ac.jp.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Kanaho
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000502:physiology*; D051379:Mice; D016501:Neurites; D009474:Neurons / Q000166:cytology / Q000378:metabolism*
chemical_list: D000089982:ADP-Ribosylation Factor 6; C542460:Acap3 protein, mouse; D020690:GTPase-Activating Proteins; D026901:Membrane Transport Proteins; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse
keywords: ACAP3; Arf6; GAP; hippocampal neurons; neurite outgrowth; small GTPase