Article ; Online: Feedback mechanism for microtubule length regulation by stathmin gradients.
2014 Volume 107, Issue 12, Page(s) 2860–2871
Abstract: ... of Rac1, we find a switchlike regulation of the MT mean length by stathmin. For constitutively active Rac1 ... by stathmin. One subpopulation of the bimodal length distribution can be identified with fast-growing and long ... In this gradient, we find a stationary bimodal MT-length distribution for both mechanisms of MT growth inhibition ...
| Abstract | We formulate and analyze a theoretical model for the regulation of microtubule (MT) polymerization dynamics by the signaling proteins Rac1 and stathmin. In cells, the MT growth rate is inhibited by cytosolic stathmin, which, in turn, is inactivated by Rac1. Growing MTs activate Rac1 at the cell edge, which closes a positive feedback loop. We investigate both tubulin sequestering and catastrophe promotion as mechanisms for MT growth inhibition by stathmin. For a homogeneous stathmin concentration in the absence of Rac1, we find a switchlike regulation of the MT mean length by stathmin. For constitutively active Rac1 at the cell edge, stathmin is deactivated locally, which establishes a spatial gradient of active stathmin. In this gradient, we find a stationary bimodal MT-length distribution for both mechanisms of MT growth inhibition by stathmin. One subpopulation of the bimodal length distribution can be identified with fast-growing and long pioneering MTs in the region near the cell edge, which have been observed experimentally. The feedback loop is closed through Rac1 activation by MTs. For tubulin sequestering by stathmin, this establishes a bistable switch with two stable states: one stable state corresponds to upregulated MT mean length and bimodal MT length distributions, i.e., pioneering MTs; the other stable state corresponds to an interrupted feedback with short MTs. Stochastic effects as well as external perturbations can trigger switching events. For catastrophe-promoting stathmin, we do not find bistability. |
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| MeSH term(s) | Feedback, Physiological ; Microtubules/chemistry ; Microtubules/metabolism ; Models, Biological ; Polymerization ; Stathmin/metabolism ; rac1 GTP-Binding Protein/metabolism |
| Chemical Substances | Stathmin ; rac1 GTP-Binding Protein (EC 3.6.5.2) |
| Language | English |
| Publishing date | 2014-12-16 |
| Publishing country | United States |
| Document type | Journal Article ; Research Support, Non-U.S. Gov't |
| ZDB-ID | 218078-9 |
| ISSN | 1542-0086 ; 0006-3495 |
| ISSN (online) | 1542-0086 |
| ISSN | 0006-3495 |
| DOI | 10.1016/j.bpj.2014.10.056 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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