Depletion of NIMA-related kinase Nek2 induces aberrant self-renewal and apoptosis in stem/progenitor cells of aged muscular tissues.

Frailty of the locomotory organs has become a widespread problem in the geriatric population. The major factor leading to frailty is an age-associated decrease in muscular mass and a reduced number of muscular cells and myofibers. In aged muscular tissues, muscular satellite cells (MuSCs) are reduced due to abnormalities in their self-renewal and the induction of apoptosis. However, the molecular mechanisms connecting aging-associated physiological changes and the reduction of MuSCs are largely unknown. NIMA-related kinase 2 (Nek2), a member of the Nek family of serine/threonine kinases, was found to be downregulated in aged MuSCs/progenitors. Further, Nek2 downregulation was found to inhibit self-renewal and apoptotic cell death by activating the p53-dependent checkpoint. Attenuated NEK2 expression was also observed in the muscular tissues of elderly donors, and its function was confirmed to be conserved in humans. Overall, this study proposes a novel mechanism for inducing muscular atrophy to understand aging-associated muscular diseases.

Nek2B accelerates the progression of hepatocellular carcinoma through regulating SFRP1 to activate the Wnt/ß-catenin pathway.

PURPOSE: The purpose of this study was to clarify the expression pattern of Nek2B in hepatocellular carcinoma (HCC) and its influence on malignant phenotypes of HCC through regulating SFRP1 and the Wnt/ß-catenin pathway. METHODS: Nek2B levels in 64 paired HCC tissues and adjacent normal ones were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The correlation between Nek2B level and clinical parameters of HCC patients was analyzed. Regulatory effects of Nek2B and SFRP1 on clonality, proliferation and apoptosis of MHCC97H and Hep3B cells were determined through functional experiments. Western blot was conducted to detect protein levels of SFRP1, ß-catenin, c-myc, cyclinD1 and MMP7 in HCC cells with overexpression or knockdown of Nek2B. At last, rescue experiments were performed to clarify the role of Nek2B/SFRP1 regulatory loop in aggravating the progression of HCC. RESULTS: Nek2B was upregulated in HCC tissues and cells. HCC patients expressing a high level of Nek2B were in more advanced tumor stage and had worse prognosis. Overexpression of Nek2B in MHCC97H cells enhanced clonality, 5-Ethynyl-2'- deoxyuridine (EdU)-positive ratio and suppressed apoptosis. Besides, knockdown of Nek2B in Hep3B cells yielded the opposite results. SFRP1 was downregulated in HCC, and low level of SFRP1 predicted worse prognosis of HCC. Overexpression of Nek2B downregulated SFRP1, but upregulated ß-catenin, c-myc, cyclinD1 and MMP7 in HCC cells. Importantly, Nek2B/SFRP1 regulatory loop was identified to aggravate the progression of HCC. CONCLUSIONS: Nek2B is upregulated in HCC, and closely linked to tumor stage and poor prognosis in HCC patients. Through interaction with SFRP1, Nek2B aggravates the progression of HCC by activating the Wnt/ß-catenin pathway.

Counterregulation of cAMP-directed kinase activities controls ciliogenesis.

The primary cilium emanates from the cell surface of growth-arrested cells and plays a central role in vertebrate development and tissue homeostasis. The mechanisms that control ciliogenesis have been extensively explored. However, the intersection between GPCR signaling and the ubiquitin pathway in the control of cilium stability are unknown. Here we observe that cAMP elevation promotes cilia resorption. At centriolar satellites, we identify a multimeric complex nucleated by PCM1 that includes two kinases, NEK10 and PKA, and the E3 ubiquitin ligase CHIP. We show that NEK10 is essential for ciliogenesis in mammals and for the development of medaka fish. PKA phosphorylation primes NEK10 for CHIP-mediated ubiquitination and proteolysis resulting in cilia resorption. Disarrangement of this control mechanism occurs in proliferative and genetic disorders. These findings unveil a pericentriolar kinase signalosome that efficiently links the cAMP cascade with the ubiquitin-proteasome system, thereby controlling essential aspects of ciliogenesis.

An evolutionarily conserved NIMA-related kinase directs rhizoid tip growth in the basal land plant Marchantia polymorpha.

Tip growth is driven by turgor pressure and mediated by the polarized accumulation of cellular materials. How a single polarized growth site is established and maintained is unclear. Here, we analyzed the function of NIMA-related protein kinase 1 (MpNEK1) in the liverwort Marchantia polymorpha In the wild type, rhizoid cells differentiate from the ventral epidermis and elongate through tip growth to form hair-like protrusions. In Mpnek1 knockout mutants, rhizoids underwent frequent changes in growth direction, resulting in a twisted and/or spiral morphology. The functional MpNEK1-Citrine protein fusion localized to microtubule foci in the apical growing region of rhizoids. Mpnek1 knockouts exhibited increases in both microtubule density and bundling in the apical dome of rhizoids. Treatment with the microtubule-stabilizing drug taxol phenocopied the Mpnek1 knockout. These results suggest that MpNEK1 directs tip growth in rhizoids through microtubule organization. Furthermore, MpNEK1 expression rescued ectopic outgrowth of epidermal cells in the Arabidopsis thaliana nek6 mutant, strongly supporting an evolutionarily conserved NEK-dependent mechanism of directional growth. It is possible that such a mechanism contributed to the evolution of the early rooting system in land plants.

NEK2 Promotes Aerobic Glycolysis in Multiple Myeloma Through Regulating Splicing of Pyruvate Kinase.

BACKGROUND: Aerobic glycolysis, a hallmark of cancer, is characterized by increased metabolism of glucose and production of lactate in normaxia. Recently, pyruvate kinase M2 (PKM2) has been identified as a key player for regulating aerobic glycolysis and promoting tumor cell proliferation and survival. METHODS: Tandem affinity purification followed up by mass spectrometry (TAP-MS) and co-immunoprecipitation (Co-IP) were used to study the interaction between NIMA (never in mitosis gene A)-related kinase 2 (NEK2) and heterogeneous nuclear ribonucleoproteins (hnRNP) A1/2. RNA immunoprecipitation (RIP) was performed to identify NEK2 binding to PKM pre-mRNA sequence. Chromatin-immunoprecipitation (ChIP)-PCR was performed to analyze a transcriptional regulation of NEK2 by c-Myc. Western blot and real-time PCR were executed to analyze the regulation of PKM2 by NEK2. RESULTS: NEK2 regulates the alternative splicing of PKM immature RNA in multiple myeloma cells by interacting with hnRNPA1/2. RIP shows that NEK2 binds to the intronic sequence flanking exon 9 of PKM pre-mRNA. Knockdown of NEK2 decreases the ratio of PKM2/PKM1 and also other aerobic glycolysis genes including GLUT4, HK2, ENO1, LDHA, and MCT4. Myeloma patients with high expression of NEK2 and PKM2 have lower event-free survival and overall survival. Our data indicate that NEK2 is transcriptionally regulated by c-Myc in myeloma cells. Ectopic expression of NEK2 partially rescues growth inhibition and cell death induced by silenced c-Myc. CONCLUSIONS: Our studies demonstrate that NEK2 promotes aerobic glycolysis through regulating splicing of PKM and increasing the PKM2/PKM1 ratio in myeloma cells which contributes to its oncogenic activity.

Hepatoma cell functions modulated by NEK2 are associated with liver cancer progression.

NEK2 (NIMA-related expressed kinase 2) is a serine/threonine centrosomal kinase that acts as a critical regulator of centrosome structure and function. Aberrant NEK2 activities lead to failure in regulating centrosome duplication. NEK2 overexpression promotes tumorigenesis and is associated with poor prognosis in several cancers. Increased NEK2 expression during the late pathological stage has been detected in the Oncomine liver dataset and hepatocellular carcinoma (HCC) specimens. Elevated NEK2 protein is associated with poor overall survival in patients with HCC. However, the precise roles and mechanisms of NEK2 in liver cancer progression remain largely unknown. An earlier functional study revealed that NEK2 mediates drug resistance (cisplatin or lipo-doxorubicin) via expression of an ABCC10 transporter. Active angiogenesis and metastasis underlie the rapid recurrence and poor survival of HCC. Results from the current study showed that NEK2 mediates tumor growth, metastasis and angiogenesis in vivo. NEK2-mediated drug resistance was blocked by a specific PI3K or AKT inhibitor. Moreover, NEK2 mediated liver cancer cell migration via pAKT/NF-κB signaling and matrix metalloproteinase (MMP) activation. Angiogenesis was induced via the same signaling pathway and IL-8 stimulation. Our findings collectively indicate that NEK2 modulates hepatoma cell functions, including growth, drug resistance, metastasis and angiogenesis via downstream genes activation.

Dishevelled is a NEK2 kinase substrate controlling dynamics of centrosomal linker proteins.

Dishevelled (DVL) is a key scaffolding protein and a branching point in Wnt signaling pathways. Here, we present conclusive evidence that DVL regulates the centrosomal cycle. We demonstrate that DVL dishevelled and axin (DIX) domain, but not DIX domain-mediated multimerization, is essential for DVL's centrosomal localization. DVL accumulates during the cell cycle and associates with NIMA-related kinase 2 (NEK2), which is able to phosphorylate DVL at a multitude of residues, as detected by a set of novel phospho-specific antibodies. This creates interfaces for efficient binding to CDK5 regulatory subunit-associated protein 2 (CDK5RAP2) and centrosomal Nek2-associated protein 1 (C-NAP1), two proteins of the centrosomal linker. Displacement of DVL from the centrosome and its release into the cytoplasm on NEK2 phosphorylation is coupled to the removal of linker proteins, an event necessary for centrosomal separation and proper formation of the mitotic spindle. Lack of DVL prevents NEK2-controlled dissolution of loose centrosomal linker and subsequent centrosomal separation. Increased DVL levels, in contrast, sequester centrosomal NEK2 and mimic monopolar spindle defects induced by a dominant negative version of this kinase. Our study thus uncovers molecular crosstalk between centrosome and Wnt signaling.

Targeting NEK2 as a promising therapeutic approach for cancer treatment.

Never in Mitosis (NIMA) Related Kinase 2 (NEK2) plays a key role in regulating mitotic processes, including centrosome duplication and separation, microtubule stabilization, kinetochore attachment and spindle assembly checkpoint. NEK2 is aberrantly overexpressed in a wide variety of human cancers and has been implicated in various aspects of malignant transformation, including tumorigenesis, drug resistance and tumor progression. The close relationship between NEK2 and cancer has made it an attractive target for anticancer therapeutic development; however, the mechanisms of how NEK2 coordinates altered signaling to malignant transformation remains unclear. In this paper, we discuss the functional roles of NEK2 in cancer development; highlight some of the significant NEK2 signaling in cancer, and summarize recent advances in the development of NEK2 inhibitors.

The potential role of the NEK6, AURKA, AURKB, and PAK1 genes in adenomatous colorectal polyps and colorectal adenocarcinoma.

Colorectal adenomatous polyp (CRAP) is a major risk factor for the development of sporadic colorectal cancer (CRC). Histone modifications are one of the epigenetic mechanisms that may have key roles in the carcinogenesis of CRC. The objective of the present study is to investigate the alternations in the defined histone modification gene expression profiles in patients with CRAP and CRC. Histone modification enzyme key gene expressions of the CRC, CRAP, and control groups were evaluated and compared using the reverse transcription PCR (RT-PCR) array method. Gene expression analysis was performed in the CRAP group after dividing the patients into subgroups according to the polyp diameter, pathological results, and morphological parameters which are risk factors for developing CRC in patients with CRAP. PAK1, NEK6, AURKA, AURKB, HDAC1, and HDAC7 were significantly more overexpressed in CRC subjects compared to the controls (p < 0.05). PAK1, NEK6, AURKA, AURKB, and HDAC1 were significantly more overexpressed in the CRAP group compared to the controls (p < 0.005). There were no significant differences between the CRAP and CRC groups with regards to PAK1, NEK6, AURKA, or AURKB gene overexpression. PAK1, NEK6, AURKA, and AURKB were significantly in correlation with the polyp diameter as they were more overexpressed in polyps with larger diameters. In conclusion, overexpressions of NEK6, AURKA, AURKB, and PAK1 genes can be used as predictive markers to decide the colonoscopic surveillance intervals after the polypectomy procedure especially in polyps with larger diameters.