title: Modulation of the stathmin-like microtubule destabilizing activity of RB3, a neuron-specific member of the SCG10 family, by its N-terminal domain.
abstract: RB3 is a neuron-specific homologue of the SCG10/stathmin family proteins, possessing a unique N-terminal membrane-associated domain and the stathmin-like domain at the C terminus, which promotes microtubule (MT) catastrophe and/or tubulin sequestering. We examined herein the contribution of the N-terminal subdomain of RB3 to the regulation of MT dynamics. To begin with, we determined the effects of full-length (RB3-f) and short truncated (RB3-s) forms of RB3 on the polymerization of MT in vitro. RB3-s had a deletion of amino acids 1-75 from the N terminus, leaving the so-called stathmin-like domain, consisting of residues 76-217. Although both RB3-f and RB3-s exhibited MT-depolymerizing activity, RB3-f was less effective. The binding affinity for tubulin was also lower in RB3-f. Direct observation of the dynamics of individual MTs using dark field microscopy revealed that RB3-s slowed MT elongation velocity, increased catastrophes, and reduced rescues. This effect is almost identical to that by stathmin/oncoprotein 18. On the other hand, the MT elongation rate increased at lower concentrations of RB3-f. In addition, RB3-f, indicated higher rescue frequency than control as well as the catastrophe in a dose-dependent manner. The functionality of RB3-f indicated that full-length RB3 has not only stathmin-like MT destabilizing activity but also MT-associated protein-like MT stabilizing activity. Possibly, the balance of these activities is altered in a concentration-dependent manner in vitro. This interesting regulatory role of the unique N-terminal domain of RB3 in MT dynamics would contribute to the physiological regulation of neuronal morphogenesis.
authors.affiliation: Department of Molecular Genetics and Aging Intervention, National Institute for Longevity Sciences, 36-3 Gengo, Morioka, Oobu, Aichi 474-8522, Japan.
authors.forename: Chitose
authors.initials: C
authors.lastname: Nakao
authors.forename: Tomohiko J
authors.initials: TJ
authors.lastname: Itoh
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Hotani
authors.forename: Nozomu
authors.initials: N
authors.lastname: Mori
mesh_terms: D000818:Animals; D001665:Binding Sites; D002454:Cell Differentiation; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D009414:Nerve Growth Factors / Q000378:metabolism*; D009474:Neurons / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000378:metabolism
chemical_list: D009414:Nerve Growth Factors; C112286:Stmn4 protein, rat; D014404:Tubulin