Stathmin strongly increases the minus end catastrophe frequency and induces rapid treadmilling of bovine brain microtubules at steady state in vitro.
Stathmin is a ubiquitous microtubule destabilizing protein that is believed to play an important role linking cell signaling to the regulation of microtubule dynamics. Here we show that stathmin strongly destabilizes microtubule minus ends in vitro at steady state, conditions in which the soluble tubulin and microtubule levels remain constant. Stathmin increased the minus end catastrophe frequency approximately 13-fold at a stathmin:tubulin molar ratio of 1:5. Stathmin steady-state catastrophe-promoting activity was considerably stronger at the minus ends than at the plus ends. Consistent with its ability to destabilize minus ends, stathmin strongly increased the treadmilling rate of bovine brain microtubules. By immunofluorescence microscopy, we also found that stathmin binds to purified microtubules along their lengths in vitro. Co-sedimentation of purified microtubules polymerized in the presence of a 1:5 initial molar ratio of stathmin to tubulin yielded a binding stoichiometry of 1 mol of stathmin per approximately 14.7 mol of tubulin in the microtubules. The results firmly establish that stathmin can increase the steady-state catastrophe frequency by a direct action on microtubules, and furthermore, they indicate that an important regulatory action of stathmin in cells may be to destabilize microtubule minus ends.
Manna
Tapas
T
Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
Thrower
Douglas
D
Miller
Herbert P
HP
Curmi
Patrick
P
Wilson
Leslie
L
D000818:Animals; D001369:Axons; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006160:Guanosine Triphosphate / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008868:Microtubule Proteins / Q000737:chemistry; D008869:Microtubule-Associated Proteins / Q000737:chemistry*; D008870:Microtubules / Q000378:metabolism*; D009068:Movement; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D011108:Polymers / Q000737:chemistry; D050777:Stathmin / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; D011108:Polymers; D050777:Stathmin; D006160:Guanosine Triphosphate