Mechanism for the catastrophe-promoting activity of the microtubule destabilizer Op18/stathmin

Abstract

Regulation of microtubule dynamic instability is crucial for cellular processes, ranging from mitosis to membrane transport. Stathmin (also known as oncoprotein 18/Op18) is a prominent microtubule destabilizer that acts preferentially on microtubule minus ends. Stathmin has been studied intensively because of its association with multiple types of cancer, but its mechanism of action remains controversial. Two models have been proposed. One model is that stathmin promotes microtubule catastrophe indirectly, and does so by sequestering tubulin; the other holds that stathmin alters microtubule dynamics by directly destabilizing growing microtubules. Stathmin's sequestration activity is well established, but the mechanism of any direct action is mysterious because stathmin binds to microtubules very weakly. To address these issues, we have studied interactions between stathmin and varied tubulin polymers. We show that stathmin binds tightly to Dolastatin-10 tubulin rings, which mimic curved tubulin protofilaments, and that stathmin depolymerizes stabilized protofilament-rich polymers. These observations lead us to propose that stathmin promotes catastrophe by binding to and acting upon protofilaments exposed at the tips of growing microtubules. Moreover, we suggest that stathmin's minus-end preference results from interactions between stathmin's N terminus and the surface of α-tubulin that is exposed only at the minus end. Using computational modeling of microtubule dynamics, we show that these mechanisms could account for stathmin's observed activities in vitro, but that both the direct and sequestering activities are likely to be relevant in a cellular context. Taken together, our results suggest that stathmin can promote catastrophe by direct action on protofilament structure and interactions.Zn-sheets | GMPCPP | T 2 S complex | computer simulation

Mechanism of microtubule lumen entry for the α-tubulin acetyltransferase enzyme αTAT1

“…4B). It has been previously demonstrated that opened, damaged microtubules can be created by briefly exposing GMPCPP microtubules to calcium (33). Therefore, rhodamine-labeled GMPCPP microtubules were briefly incubated with 40 mM CaCl 2 , and the CaCl 2 -treated microtubules were imaged with TEM (Fig.…”

Coordinating Neuronal Actin–Microtubule Dynamics

“…Polymerisation and catastrophe events occur more rapidly at the microtubule plus end, although minus ends also exhibit dynamic lengthening and shortening [17]. For example, stathmin promotes microtubule instability either by sequestering ab-tubulin heterodimers or by binding to and destabilising exposed microtubule protofilaments at both the plus and minus ends, promoting catastrophe events [93]. The disordered tails of a-and b-tubulin are major sites for post-translational modifications, which may either intrinsically influence microtubule stability or regulate the binding specificities of microtubuleassociated proteins (MAPs) [18,[94][95][96].…”

Microtubules in 3D cell motility

“…Another specific factor that controls microtubule assembly and has been linked to 3D cell motility is the tubulin-binding protein stathmin, a tubulin-sequestering and microtubule-destabilizing protein (Gupta et al, 2013;Steinmetz, 2007). Its inhibition through apoptosis regulatory protein (Siva1) has been associated with microtubule stabilization, reduced 3D matrix invasion, and suppression of EMT and metastasis in a breast cancer model (Li et al, 2011b).…”