title: Differential control of the NIMA-related kinases, Nek6 and Nek7, by serum stimulation.
abstract: Neks (NIMA-related kinases) are mammalian serine/threonine (Ser/Thr) protein kinases structurally related to Aspergillus NIMA (Never in Mitosis, gene A), which plays essential roles in mitotic signaling. Among these kinases, Nek6 and Nek7 are structurally related and constitute a subfamily in the NIMA/Nek family, although their functions still remain almost elusive. In this report, we studied the enzymatic regulation of Nek6 and Nek7 to gain an insight into their cellular functions. Recombinant Nek7 produced in bacteria was active comparably to Nek6; however, the Nek7 activity in mammalian cells was found to be significantly lower than Nek6. Since Nek6 previously has been reported to in vitro phosphorylate p70 ribosomal S6 kinase at Thr412, we examined if Nek6 and Nek7 activities were controlled by the amino acid supplement, which is known to affect the phosphorylation at Thr412, and did not observe any significant effect. However, we unexpectedly found that Nek7 kinase activity was rapidly and efficiently increased by serum deprivation, while Nek6 activity was decreased. This is well consistent with the lower activity of Nek7 in cells under normal growth conditions. In addition, it was suggested that Nek7 activity would be regulated in a cell cycle-dependent manner, although Nek6 was not. These clear differences in enzymatic control between the highly similar kinases, Nek6 and Nek7, suggest their distinct signaling functions in mammalian cells.
authors.affiliation: Division of Molecular and Cellular Immunology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, 812-8582, Fukuoka, Japan. minoguch@ims.u-tokyo.ac.jp
authors.forename: Shigeru
authors.initials: S
authors.lastname: Minoguchi
authors.forename: Mayu
authors.initials: M
authors.lastname: Minoguchi
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshimura
mesh_terms: D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002453:Cell Cycle; D003470:Culture Media; D015536:Down-Regulation; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D000072379:NIMA-Related Kinases; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D003470:Culture Media; D011993:Recombinant Fusion Proteins; C512685:NEK7 protein, human; D000072379:NIMA-Related Kinases; C442331:NIMA-related kinase 6; C512686:Nek7 protein, mouse; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa