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Vol. 19, Issue 5, 1952-1961, May 2008

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Ste20-related Protein Kinase LOSK (SLK) Controls Microtubule Radial Array in Interphase

Anton V. Burakov^*,,, Olga N. Zhapparova^*,,, Olga V. Kovalenko^,, Liudmila A. Zinovkina, Ekaterina S. Potekhina, Nina A. Shanina, Dieter G. Weiss^||, Sergei A. Kuznetsov^||, and Elena S. Nadezhdina^*,

*Institute of Protein Research, Russian Academy of Science, 142290 Pushchino, Moscow Region, Russian Federation; A. N. Belozersky Institute of Physico-Chemical Biology and Biology Faculty of M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation; and ^||Institute of Biological Sciences, Cell Biology and Biosystems Technology, University of Rostock, D-18059 Rostock, Germany

Submitted December 29, 2006; Revised January 29, 2008; Accepted February 8, 2008
Monitoring Editor: Yixian Zheng

Interphase microtubules are organized into a radial array with centrosome in the center. This organization is a subject of cellular regulation that can be driven by protein phosphorylation. Only few protein kinases that regulate microtubule array in interphase cells have been described. Ste20-like protein kinase LOSK (SLK) was identified as a microtubule and centrosome-associated protein. In this study we have shown that the inhibition of LOSK activity by dominant-negative mutant K63R-T or by LOSK depletion with RNAi leads to unfocused microtubule arrangement. Microtubule disorganization is prominent in Vero, CV-1, and CHO-K1 cells but less distinct in HeLa cells. The effect is a result neither of microtubule stabilization nor of centrosome disruption. In cells with suppressed LOSK activity centrosomes are unable to anchor or to cap microtubules, though they keep nucleating microtubules. These centrosomes are depleted of dynactin. Vero cells overexpressing K63R-T have normal dynactin "comets" at microtubule ends and unaltered morphology of Golgi complex but are unable to polarize it at the wound edge. We conclude that protein kinase LOSK is required for radial microtubule organization and for the proper localization of Golgi complex in various cell types.

These authors contributed equally to this work.

Address correspondence to: Elena Nadezhdina (enadezhdina{at}genebee.msu.ru)

Abbreviations used: DHC, dynein heavy chain; EGFP, enhanced green fluorescent protein; GST, glutathione-S-transferase; LOSK, long Ste20-like kinase; MBP, myelin basic protein.

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