Disease relevance of NEK2

• The centrosomal kinase Nek2 displays elevated levels of protein expression in human breast cancer [1].
• Most importantly, by immunohistochemistry, we find that Nek2 protein is significantly up-regulated in preinvasive in situ ductal carcinomas of the breast as well as in invasive breast carcinomas [1].
• In addition, our mutation screening showed that NLK was not a mutational target in breast and colorectal tumor cells [2].

High impact information on NEK2

• The focal adhesion scaffolding protein HEF1 regulates activation of the Aurora-A and Nek2 kinases at the centrosome [3].
• We also show that HEF1 depletion causes centrosomal splitting, mono-astral spindles and hyperactivation of Nek2, implying additional action earlier in the cell cycle [3].
• Nek2 activity is not required for APC/C activation [4].
• Finally, the COOH-terminal domain of C-Nap1 could readily be phosphorylated by Nek2 in vitro, as well as after coexpression of the two proteins in vivo [5].
• We also propose that phosphorylation by Nek2 may prime Nlp for phosphorylation by Plk1 [6].

Biological context of NEK2

• Based on these findings, we propose a model implicating both Nek2 and C-Nap1 in the regulation of centriole-centriole cohesion during the cell cycle [5].
• Overexpression of active Nek2 or Plk1 causes premature displacement of Nlp from interphase centrosomes [6].
• Elimination of NEK2A by small interfering RNA does not arrest cells in mitosis but causes aberrant premature chromosome segregation [7].
• These NEK2A-eliminated or -suppressed cells display a chromosome bridge phenotype with sister chromatid inter-connected [7].
• Like MAD1, NEK2A is localized to HeLa cell kinetochore of mitotic cells [7].

Anatomical context of NEK2

• The trigger for these events is likely the genetic instability arising from centrosome amplification that is associated, at least in part, with decreased expression of the NIMA-related kinase NEK2 [8].
• Coordinate regulation of the mother centriole component nlp by nek2 and plk1 protein kinases [6].
• Microtubules facilitate Nek2 trafficking to the centrosome but only over long distances [9].
• Chromosomal mapping of the nek2 gene identified two independent loci on chromosomes 1 and 14, and Northern blot analyses revealed the expression of two distinct mRNAs of approximately 2.4 and 4.7 kilobases in all human cell lines examined [10].
• Finally, by ectopic expression of Nek2A in immortalized HBL100 breast epithelial cells, we show that increased Nek2 protein leads to accumulation of multinucleated cells with supernumerary centrosomes [1].

Associations of NEK2 with chemical compounds

• Moreover, loss of NEK2A impairs mitotic checkpoint signaling in response to spindle damage by nocodazole, which affected mitotic escape and led to generation of cells with multiple nuclei [7].
• The cell cycle-regulated protein serine/threonine NIMA-related kinase 2 (Nek2), which shows a predominant localization at centrosomes, is identified as a protein which interacts with protein phosphatase 1 (PP1) using the yeast two-hybrid system [11].
• Here we show that human Hec1 is a serine phosphoprotein and that it binds specifically to the mitotic regulatory kinase Nek2 during G(2)/M [12].
• Finally, we emphasize that the Nek2 leucine zipper described here differs from classical leucine zippers in that it exhibits a radically different arrangement of hydrophobic and charged amino acids [13].
• Glycerol gradient centrifugation indicated that endogenous Nek2 is present in HeLa cells as a salt-resistant 6 S complex, the predicted size of a Nek2 homodimer [13].

Physical interactions of NEK2

• NEK2A interacts with MAD1 and possibly functions as a novel integrator of the spindle checkpoint signaling [7].

Enzymatic interactions of NEK2

• We found that Plk1 can phosphorylate Nek2 in vitro and interacts with Nek2 in vivo [14].
• Moreover, Nek2 directly phosphorylated Nek11 in the C-terminal non-catalytic region and elevated Nek11 kinase activity [15].

Other interactions of NEK2

• These observations suggest that NEK2 plays a role in mediating the actions of BRCA1 and GADD45a in regulating centrosome duplication and in maintaining genetic stability [8].
• Nek2 is a key regulator of centrosome separation and is a target of Plk1 in blocking centrosome separation [14].
• C-Nap1, a novel centrosomal coiled-coil protein and candidate substrate of the cell cycle-regulated protein kinase Nek2 [5].
• Here, we report the isolation of complementary DNAs encoding Nek2 and Nek3, two novel human protein kinases structurally related to NIMA [10].
• Dynamic recruitment of Nek2 kinase to the centrosome involves microtubules, PCM-1, and localized proteasomal degradation [9].

Analytical, diagnostic and therapeutic context of NEK2

• Consistent with failure of antisense-treated cells to enter mitosis, microarray analysis identified altered expression of NEK2 and nucleophosmin/B23 [16].
• Here we show by both immunofluorescence microscopy and biochemical fractionation that human Nek2 localizes to the centrosome [17].
• Sequencing of products generated by reverse transcriptase PCR, immunoblotting of cell extracts and transfection of antisense oligonucleotides together demonstrate that human Nek2 is expressed as two splice variants [18].

References