Stathmin family proteins display specific molecular and tubulin binding properties

Stathmin family phosphoproteins (stathmin, SCG10, SCLIP, and RB3/RB3'/RB3") are involved in signal transduction and regulation of microtubule dynamics . With the exception of stathmin, they are expressed exclusively in the ner vous system, where they display different spatio-temporal and functional re gulations and hence play at least partially distinct and possibly complemen tary roles in relation to the control of development, plasticity, and neuro nal activities. At the molecular level, each possesses a specific "stathmin -like domain" and, with the exception of stathmin, various combinations of N-terminal extensions involved in their association with intracellular memb rane compartments, We show here that each stathmin-like domain also display s specific biochemical and tubulin interaction properties. They are all abl e to sequester two alpha/beta tubulin heterodimers as revealed by their inh ibitory action on tubulin polymerization and by gel filtration. However, th ey differ in the stabilities of the complexes formed as well as in their in teraction kinetics with tubulin followed by surface plasmon resonance as fo llows: strong stability and slow kinetics for RB3; medium for SCG10, SCLIP, and stathmin; and weak stability and rapid kinetics for RB3'. These result s suggest that the fine-tuning of their stathmin-like domains contributes t o the specific functional roles of stathmin family proteins in the regulati on of microtubule dynamics within the various cell types and subcellular co mpartments of the developing or mature nervous system.