title: Rab35, acting through ACAP2 switching off Arf6, negatively regulates oligodendrocyte differentiation and myelination.
abstract: Oligodendrocyte precursor cells differentiate to produce myelin sheaths that insulate axons to ensure fast propagation of action potentials. Many aspects of differentiation are regulated by multiple extracellular signals. However, their intracellular signalings remain elusive. We show that Rab35 and its effector, ACAP2, a GTPase-activating protein that switches off Arf6 activity, negatively regulate oligodendrocyte morphological differentiation. Knockdown of Rab35 or ACAP2 with their respective small interfering RNAs promotes differentiation. As differentiation initiates, the activities of Rab35 and ACAP2 are down-regulated. The activity of Arf6, in contrast, is up-regulated. Arf6 knockdown inhibits differentiation, indicating that Rab35 and ACAP2 negatively regulate differentiation by down-regulating Arf6. Importantly, as differentiation proceeds, the activity of cytohesin-2, a guanine nucleotide exchange factor that switches on Arf6 activity, is up-regulated. Pharmacological inhibition of cytohesin-2 inhibits differentiation, suggesting that cytohesin-2 promotes differentiation by activating Arf6. Furthermore, using oligodendrocyte-neuronal cocultures, we find that knockdown of Rab35 or ACAP2 promotes myelination, whereas inhibition of cytohesin-2 or knockdown of Arf6 inhibits myelination. Thus Rab35/ACAP2 and cytohesin-2 antagonistically control oligodendrocyte differentiation and myelination through Arf6 regulation, presenting a unique small GTPase on/off switching mechanism.
authors.affiliation: Department of Pharmacology, National Research Institute for Child Health and Development, Setagaya, Tokyo 157-8535, Japan Japan Human Health Sciences Foundation, Chuo, Tokyo 103-0001, Japan Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Natsuki
authors.initials: N
authors.lastname: Yamamori
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Torii
authors.forename: Akito
authors.initials: A
authors.lastname: Tanoue
authors.forename: Junji
authors.initials: J
authors.lastname: Yamauchi
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation; D018920:Coculture Techniques; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000166:cytology; D057809:HEK293 Cells; D006801:Humans; D018345:Mice, Knockout; D009186:Myelin Sheath / Q000502:physiology; D009474:Neurons / Q000378:metabolism; D009836:Oligodendroglia / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D020691:rab GTP-Binding Proteins / Q000502:physiology*
chemical_list: C575760:ACAP2 protein, rat; D000089982:ADP-Ribosylation Factor 6; D020690:GTPase-Activating Proteins; C102474:cytohesin-2; C575759:Rab35 protein, rat; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; C000715349:Arf6 protein, rat; D020691:rab GTP-Binding Proteins