NIMA‐related kinases 6, 4, and 5 interact with each other to regulate microtubule organization during epidermal cell expansion in
NimA‐related kinase 6 (NEK6) has been implicated in microtubule regulation to suppress the ectopic outgrowth of epidermal cells; however, its molecular functions remain to be elucidated. Here, we analyze the function of NEK6 and other members of the NEK family with regard to epidermal cell expansion and cortical microtubule organization. The functional NEK6–green fluorescent protein fusion localizes to cortical microtubules, predominantly in particles that exhibit dynamic movement along microtubules. The kinase‐dead mutant of NEK6 (ibo1‐1) exhibits a disturbance of the cortical microtubule array at the site of ectopic protrusions in epidermal cells. Pharmacological studies with microtubule inhibitors and quantitative analysis of microtubule dynamics indicate excessive stabilization of cortical microtubules in ibo1/nek6 mutants. In addition, NEK6 directly binds to microtubules in vitro and phosphorylates β‐tubulin. NEK6 interacts and co‐localizes with NEK4 and NEK5 in a transient expression assay. The ibo1‐3 mutation markedly reduces the interaction between NEK6 and NEK4 and increases the interaction between NEK6 and NEK5. NEK4 and NEK5 are required for the ibo1/nek6 ectopic outgrowth phenotype in epidermal cells. These results demonstrate that NEK6 homodimerizes and forms heterodimers with NEK4 and NEK5 to regulate cortical microtubule organization possibly through the phosphorylation of β‐tubulins.
Document Type: Research Article
Affiliations: 1: Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan 2: Biology Department, University of Massachusetts, Amherst, MA 01003, USA 3: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan 4: Graduate School of Biological Science, Nara Institute of Science and Technology, Nara 630-0192, Japan 5: Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
Publication date: September 1, 2011