Kinase Subfamily NEK6

Kinase Classification: Group Other: Family NEK: Subfamily NEK6

NEK6 regulates spindle formation during mitosis and modulates cytokinesis and endocytosis, and is regulated by NEK9.

Evolution

NEK6 is found in most eukaryotes, but lost from some insects, including Drosophila, from most fungi, and from higher plants. It has two members in vertebrates, NEK6 and NEK7.

Domain Structure

NEK6 consists of a kinase domain, with a short, weakly conserved and unstructured N-terminal extension [1].

Mitosis and Cytokineses

Mammalian NEK6 and NEK7 have several shared functions. Both are activated in mitosis and required for cell cycle [2, 3]. Both are activated by the NEK9 kinase, which is activated in mitosis, and binds NEK6 via the NEK9 C-terminal tail, and is capable of phosphorylating both kinases on the activation loop [4]. Mutants typically arrest in prophase-metaphase

Several phosphorylation targets of NEK6/7 in spindle formation have been described: NEK6 and NEK7 both phosphorylate the microtubule regulator EML4, counteracting its function to stabilize microtubles [5]. NEK6 binds and phosphorylates the kinesin KIF11/Eg5 during mitosis, and the phosphoryaltion is required for bipolar spindle formation [6]. NEK6 also phosphorylates KIF20A/MKLP2 to localize it to the anaphase central spindle, while NEK7 regulates KIF14, to recruit CRIK/Citron kinase to the anaphase midzone [7]. NEK6 and NEK7 both phosphorylate the nucleoporin NUP98 in vitro and are thought to lead to nuclear envelope permeability in mitosis [8].

Endocytosis

The C. elegans member, nekl-3/F19H6.1 controls clathrin-mediated endocytosis, along with nekl-2 (NEK8 subfamily) [9, 10] . Human NEKs were able to rescue the worm mutants. The two NEKs were localized by specific ankryin repeat proteins, MLT2-4 [11]. MLT-3 interacts specifically with nekl-3, and it's mammalian homolog, Anks6, specifically interacts with Nek7, and is implicated in cilium biology. The spindle and endocytosis functions may be linked, since clathrin is also involved in mitotic spindle stabilization and centrosome function [12]. RNAi library screening of human kinases for endocytosis defects also showed NEK6 and NEK7 to be required for clathrin-mediated endocytosis, with weaker effects from NEK8 or NEK9 knockdown [9].

NEK6 and Cancer, DNA damage and senesence

NEK6 is overexpressed in several cancers, and tissue culture and xenograft studies show that drives cancer cell survival and anchorage-independent growth [13]. NEK6 was identified in a screen for mediators of castration resistance in prostate cancer [14], which also identified FOXL2 as a novel substrate. NEK6 is reported to bind SMAD4 and block its nuclear localization and block TGFb signaling [15], to bind and phosphorylate STAT3 on S727, activating it for cell transformation [16], and to bind the cancer-related prolyl hydroxylase, Pin1 [17].

NEK6 has been reported to block p53-induced senesence, and overexpression could interfere with senesence-driving cancer drugs like camptothecin and doxorubicin [18]. NEK6 is phosphorylated by UV and IR radiation, possibly through Chk1 and Chk2, and radiation blocks its mitotic activation [19]. Human NEK6 is also reported to phosphorylate the telomerase regulator TPP1 on S255 during mitosis [20].

References

1. Meirelles GV, Silva JC, Mendonça Yde A, Ramos CH, Torriani IL, and Kobarg J. Human Nek6 is a monomeric mostly globular kinase with an unfolded short N-terminal domain. BMC Struct Biol. 2011 Feb 14;11:12. DOI:10.1186/1472-6807-11-12 |
2. O'Regan L and Fry AM. The Nek6 and Nek7 protein kinases are required for robust mitotic spindle formation and cytokinesis. Mol Cell Biol. 2009 Jul;29(14):3975-90. DOI:10.1128/MCB.01867-08 |
3. Yin MJ, Shao L, Voehringer D, Smeal T, and Jallal B. The serine/threonine kinase Nek6 is required for cell cycle progression through mitosis. J Biol Chem. 2003 Dec 26;278(52):52454-60. DOI:10.1074/jbc.M308080200 |
4. Belham C, Roig J, Caldwell JA, Aoyama Y, Kemp BE, Comb M, and Avruch J. A mitotic cascade of NIMA family kinases. Nercc1/Nek9 activates the Nek6 and Nek7 kinases. J Biol Chem. 2003 Sep 12;278(37):34897-909. DOI:10.1074/jbc.M303663200 |
5. Adib R, Montgomery JM, Atherton J, O'Regan L, Richards MW, Straatman KR, Roth D, Straube A, Bayliss R, Moores CA, and Fry AM. Mitotic phosphorylation by NEK6 and NEK7 reduces the microtubule affinity of EML4 to promote chromosome congression. Sci Signal. 2019 Aug 13;12(594). DOI:10.1126/scisignal.aaw2939 |
6. Rapley J, Nicolàs M, Groen A, Regué L, Bertran MT, Caelles C, Avruch J, and Roig J. The NIMA-family kinase Nek6 phosphorylates the kinesin Eg5 at a novel site necessary for mitotic spindle formation. J Cell Sci. 2008 Dec 1;121(Pt 23):3912-21. DOI:10.1242/jcs.035360 |
7. Cullati SN, Kabeche L, Kettenbach AN, and Gerber SA. A bifurcated signaling cascade of NIMA-related kinases controls distinct kinesins in anaphase. J Cell Biol. 2017 Aug 7;216(8):2339-2354. DOI:10.1083/jcb.201512055 |
8. Laurell E, Beck K, Krupina K, Theerthagiri G, Bodenmiller B, Horvath P, Aebersold R, Antonin W, and Kutay U. Phosphorylation of Nup98 by multiple kinases is crucial for NPC disassembly during mitotic entry. Cell. 2011 Feb 18;144(4):539-50. DOI:10.1016/j.cell.2011.01.012 |
9. Joseph BB, Wang Y, Edeen P, Lažetić V, Grant BD, and Fay DS. Control of clathrin-mediated endocytosis by NIMA family kinases. PLoS Genet. 2020 Feb;16(2):e1008633. DOI:10.1371/journal.pgen.1008633 |
10. Yochem J, Lažetić V, Bell L, Chen L, and Fay D. C. elegans NIMA-related kinases NEKL-2 and NEKL-3 are required for the completion of molting. Dev Biol. 2015 Feb 15;398(2):255-66. DOI:10.1016/j.ydbio.2014.12.008 |
11. Lažetić V and Fay DS. Conserved Ankyrin Repeat Proteins and Their NIMA Kinase Partners Regulate Extracellular Matrix Remodeling and Intracellular Trafficking in Caenorhabditis elegans. Genetics. 2017 Jan;205(1):273-293. DOI:10.1534/genetics.116.194464 |
12. Royle SJ. The role of clathrin in mitotic spindle organisation. J Cell Sci. 2012 Jan 1;125(Pt 1):19-28. DOI:10.1242/jcs.094607 |
13. Nassirpour R, Shao L, Flanagan P, Abrams T, Jallal B, Smeal T, and Yin MJ. Nek6 mediates human cancer cell transformation and is a potential cancer therapeutic target. Mol Cancer Res. 2010 May;8(5):717-28. DOI:10.1158/1541-7786.MCR-09-0291 |
14. Choudhury AD, Schinzel AC, Cotter MB, Lis RT, Labella K, Lock YJ, Izzo F, Guney I, Bowden M, Li YY, Patel J, Hartman E, Carr SA, Schenone M, Jaffe JD, Kantoff PW, Hammerman PS, and Hahn WC. Castration Resistance in Prostate Cancer Is Mediated by the Kinase NEK6. Cancer Res. 2017 Feb 1;77(3):753-765. DOI:10.1158/0008-5472.CAN-16-0455 |
15. Zuo J, Ma H, Cai H, Wu Y, Jiang W, and Yu L. An inhibitory role of NEK6 in TGFβ/Smad signaling pathway. BMB Rep. 2015 Aug;48(8):473-8. DOI:10.5483/bmbrep.2015.48.8.225 |
16. Jeon YJ, Lee KY, Cho YY, Pugliese A, Kim HG, Jeong CH, Bode AM, and Dong Z. Role of NEK6 in tumor promoter-induced transformation in JB6 C141 mouse skin epidermal cells. J Biol Chem. 2010 Sep 3;285(36):28126-33. DOI:10.1074/jbc.M110.137190 |
17. Chen J, Li L, Zhang Y, Yang H, Wei Y, Zhang L, Liu X, and Yu L. Interaction of Pin1 with Nek6 and characterization of their expression correlation in Chinese hepatocellular carcinoma patients. Biochem Biophys Res Commun. 2006 Mar 24;341(4):1059-65. DOI:10.1016/j.bbrc.2005.12.228 |
18. Jee HJ, Kim HJ, Kim AJ, Song N, Kim M, and Yun J. Nek6 suppresses the premature senescence of human cancer cells induced by camptothecin and doxorubicin treatment. Biochem Biophys Res Commun. 2011 May 20;408(4):669-73. DOI:10.1016/j.bbrc.2011.04.083 |
19. Lee MY, Kim HJ, Kim MA, Jee HJ, Kim AJ, Bae YS, Park JI, Chung JH, and Yun J. Nek6 is involved in G2/M phase cell cycle arrest through DNA damage-induced phosphorylation. Cell Cycle. 2008 Sep 1;7(17):2705-9. DOI:10.4161/cc.7.17.6551 |
20. Hirai Y, Tamura M, Otani J, and Ishikawa F. NEK6-mediated phosphorylation of human TPP1 regulates telomere length through telomerase recruitment. Genes Cells. 2016 Aug;21(8):874-89. DOI:10.1111/gtc.12391 |
21. Ramachandran H, Engel C, Müller B, Dengjel J, Walz G, and Yakulov TA. Anks3 alters the sub-cellular localization of the Nek7 kinase. Biochem Biophys Res Commun. 2015 Aug 28;464(3):901-7. DOI:10.1016/j.bbrc.2015.07.063 |
22. Pelkmans L, Fava E, Grabner H, Hannus M, Habermann B, Krausz E, and Zerial M. Genome-wide analysis of human kinases in clathrin- and caveolae/raft-mediated endocytosis. Nature. 2005 Jul 7;436(7047):78-86. DOI:10.1038/nature03571 |