Mechanistic basis of Nek7 activation through Nek9 binding and induced dimerization

NEK kinases in cell cycle regulation, DNA damage response, and cancer progression

The NIMA-related kinase (NEK) family of serine/threonine kinases is essential for the regulation of cell cycle progression, mitotic spindle assembly, and genomic stability. In this review, we explore the structural and functional diversity of NEK kinases, highlighting their roles in both canonical and non-canonical cellular processes. We examine recent preclinical findings on NEK inhibition, showcasing promising results for NEK-targeted therapies, particularly in cancer types characterized by high NEK expression. We discussed the therapeutic potential of targeting NEKs as modulators of cell cycle and DDR pathways, with a focus on identifying strategies to exploit NEK activity for enhanced treatment efficacy. Future research directions are proposed to further elucidate NEK-mediated mechanisms and to develop selective inhibitors that target NEK-related pathways.

Microtubule Association of EML4-ALK V3 Is Key for the Elongated Cell Morphology and Enhanced Migration Observed in V3 Cells

The EML4-ALK oncogene drives tumour progression in approximately 5% of cases of non-small-cell lung cancers. At least 15 EML4-ALK variants have been identified, which elicit differential responses to conventional ALK inhibitors. Unfortunately, most, if not all, patients eventually acquire resistance to these inhibitors and succumb to the disease, which warrants the need for alternative targets to be identified. The most aggressive variant, EML4-ALK variant 3 (V3), assembles into a complex on interphase microtubules together with the NEK9 and NEK7 kinases, which leads to the downstream phosphorylation of NEK7 substrates. Overall, this promotes an elongated cell morphology and an enhanced migratory phenotype, which likely contributes to the increased metastasis often seen in V3 patients. Here, using two separate approaches to displace V3 from microtubules and a variety of in vitro assays, we show that microtubule association of EML4-ALK V3 is required for both V3 phenotypes, as removal of the oncogenic fusion protein from microtubules led to the dissociation of the V3-NEK9-NEK7 complex and the reversal of both phenotypic changes. Overall, we propose that targeting the interaction between EML4-ALK V3 and microtubules might offer a novel therapeutic option, independent of ALK activity, for V3+ NSCLC patients with acquired resistance to ALK inhibitors.

AS160 is a lipid-responsive regulator of cardiac Ca2+ homeostasis by controlling lysophosphatidylinositol metabolism and signaling

The obese heart undergoes metabolic remodeling and exhibits impaired calcium (Ca2+) homeostasis, which are two critical assaults leading to cardiac dysfunction. The molecular mechanisms underlying these alterations in obese heart are not well understood. Here, we show that the Rab-GTPase activating protein AS160 is a lipid-responsive regulator of Ca2+ homeostasis through governing lysophosphatidylinositol metabolism and signaling. Palmitic acid/high fat diet inhibits AS160 activity through phosphorylation by NEK6, which consequently activates its downstream target Rab8a. Inactivation of AS160 in cardiomyocytes elevates cytosolic Ca2+ that subsequently impairs cardiac contractility. Mechanistically, Rab8a downstream of AS160 interacts with DDHD1 to increase lysophosphatidylinositol metabolism and signaling that leads to Ca2+ release from sarcoplasmic reticulum. Inactivation of NEK6 prevents inhibition of AS160 by palmitic acid/high fat diet, and alleviates cardiac dysfunction in high fat diet-fed mice. Together, our findings reveal a regulatory mechanism governing metabolic remodeling and Ca2+ homeostasis in obese heart, and have therapeutic implications to combat obesity cardiomyopathy.

Remembering Andrew Fry (1966-2024)

In this article we reflect on the life and work of Andrew Fry, a renowned molecular cell biologist and a cherished member of the scientific community at the University of Leicester, UK, who passed away on 30th April 2024 at the age of 57. His groundbreaking work on the cellular mechanisms of Never in Mitosis gene-A related kinases (Neks) made an indelible mark on the field. Alongside his scientific achievements, Andrew was an exceptional mentor, a thoughtful academic leader and a dependable collaborator. To understand what motivated Andrew, we first need to look into his background.

Genetically evaluating the causal role of peripheral immune cells in colorectal cancer: a two-sample Mendelian randomization study

BACKGROUND

Investigating novel therapeutic strategies for colorectal cancer (CRC) is imperative. However, there is limited research on the use of drugs to target peripheral blood immune cells in this context. To address this gap, we performed a two-sample Mendelian randomization (MR) analysis to identify potential therapeutic targets for CRC.

METHODS

We applied two-sample MR to identify the causal relationship between peripheral blood immune cells and CRC. GWAS data were obtained from the IEU OPEN GWAS project. Based on the implications from the MR results, we conducted a comprehensive database search and genetic analysis to explore potential underlying mechanisms. We predicted miRNAs for each gene and employed extensive research for potential therapeutic applications.

RESULTS

We have identified causal associations between two peripheral immune cells and colorectal cancer. Activated & resting Treg %CD4 + cell was positively associated with the risks of CRC, while DN (CD4-CD8-) %leukocyte cell exhibited a protective role in tumor progression. NEK7 (NIMA related kinase 7) and LHX9 (LIM homeobox 9) expressed in Treg cells were positively associated with CRC risks and may play a vital role in carcinogenesis.

CONCLUSIONS

This study identified causal relationship between peripheral immune cell and CRC. Treg and DN T cells were implicated to own promoting and inhibiting effects on CRC progression respectively. NEK7 and LHX9 in Treg cells were identified as potential biotarget for antitumor therapies.

Synthesis, biological evaluation and in silico investigations of benzotriazole derivatives as potential inhibitors of NIMA related kinase

In the current study, a novel compound, bis(3-(2H-benzo[d][1,2,3]triazol-2-yl)-2-(prop-2-yn-1-yloxy)-5-(2,4,4-trimethylpentan-2-yl)phenyl)methane (TAJ1), has been synthesized by the reaction of 6,6'-methylenebis(2-(2H-benzo[d][1,2,3]triazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)phenol) (1), propargyl bromide (2) and potassium carbonate. Spectroscopic (FTIR, 1H-NMR, 13C-NMR) and single-crystal assays proved the structure of the synthesized sample. XRD analysis confirmed the structure of the synthesized compound, showing that it possesses two aromatic parts linked via a -CH2 carbon with a bond angle of 108.40°. The cell line activity reported a percent growth reduction for different cell types (HeLa cells, MCF-7 cells, and Vero cells) under various treatment conditions (TAJ1, cisplatin, and doxorubicin) after 24 hours and 48 hours. The percent growth reduction represents a decrease in cell growth compared to a control condition. Furthermore, density functional theory (DFT) calculations were utilized to examine the frontier molecular orbitals (FMOs) and overall chemical reactivity descriptors of TAJ1. The molecule's chemical reactivity and stability were assessed by determining the HOMO-LUMO energy gap. TAJ1 displayed a HOMO energy level of -0.224 eV, a LUMO energy level of -0.065 eV, and a HOMO-LUMO gap of 0.159 eV. Additionally, molecular docking analysis was performed to assess the binding affinities of TAJ1 with various proteins. The compound TAJ1 showed potent interactions with NEK2, exhibiting -10.5 kcal mol-1 binding energy. Although TAJ1 has demonstrated interactions with NEK7, NEK9, TP53, NF-KAPPA-B, and caspase-3 proteins, suggesting its potential as a therapeutic agent, it is important to evaluate the conformational stability of the protein-ligand complex. Hence, molecular dynamics simulations were conducted to assess this stability. To analyze the complex, root mean square deviation (RMSD) and root mean square fluctuation analyses were performed. The results of these analyses indicate that the top hits obtained from the virtual screening possess the ability to act as effective NEK2 inhibitors. Therefore, further investigation of the inhibitory potential of these identified compounds using in vitro and in vivo approaches is recommended.

ALK-JNK signaling promotes NLRP3 inflammasome activation and pyroptosis via NEK7 during Streptococcus pneumoniae infection

Streptococcus pneumoniae (S. pneumoniae), a clinically important pathogen worldwide, causes serious invasive diseases, such as pneumonia, otitis media, and meningitis. The NLR family pyrin domain-containing 3 (NLRP3) inflammasome, an important component of the innate immune system, plays a key role in defense against pathogen infection; however the specific activation mechanism induced by S. pneumoniae infection is not fully understood. Here, primary mouse macrophages were selected as the in vitro cell model, and the effect of kinases on S. pneumoniae infection-induced NLRP3 inflammasome activation was investigated in vivo and in vitro using the western blot/RT-PCR/Co-IP/immunofluorescence staining/ELISA with or without kinase inhibitor or siRNA pretreatment. In this study, we found that the formation of the NEK7-NLRP3 complex significantly increased during S. pneumoniae infection and that anaplastic lymphoma kinase (ALK) and Jun N-terminal kinase (JNK) were phosphorylated rapidly. ALK and JNK inhibitors significantly reduced the ability of bacterial killing, the gene expression of NLRP3 inflammasome, the formation of apoptosis-associated speck-like protein containing caspase-recruitment domain (ASC) specks and the NEK7-NLRP3 complex, which in turn decreased the activation level of NLRP3 inflammasome-associated molecules and the maturation of interleukin-1β (IL-1β). In addition, ALK regulated the phosphorylation of JNK. Interestingly, the ALK/JNK/NEK7-NLRP3 signaling pathway is also involved in regulating pyroptosis and IL-1β secretion triggered by S. pneumoniae infection. In conclusion, our data suggest, for the first time, that the ALK/JNK/NEK7-NLRP3 signaling pathway may play an important role in NLRP3 inflammasome activation and pyroptosis and consequently regulate the host immune response upon S. pneumoniae infection.

Structural Mechanisms of NLRP3 Inflammasome Assembly and Activation

As an important sensor in the innate immune system, NLRP3 detects exogenous pathogenic invasions and endogenous cellular damage and responds by forming the NLRP3 inflammasome, a supramolecular complex that activates caspase-1. The three major components of the NLRP3 inflammasome are NLRP3, which captures the danger signals and recruits downstream molecules; caspase-1, which elicits maturation of the cytokines IL-1β and IL-18 and processing of gasdermin D to mediate cytokine release and pyroptosis; and ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain), which functions as a bridge connecting NLRP3 and caspase-1. In this article, we review the structural information that has been obtained on the NLRP3 inflammasome and its components or subcomplexes, with special focus on the inactive NLRP3 cage, the active NLRP3-NEK7 (NIMA-related kinase 7)-ASC inflammasome disk, and the PYD-PYD and CARD-CARD homotypic filamentous scaffolds of the inflammasome. We further implicate structure-derived mechanisms for the assembly and activation of the NLRP3 inflammasome.

Exosomal miR-23b-3p from bone mesenchymal stem cells alleviates experimental autoimmune encephalomyelitis by inhibiting microglial pyroptosis

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system and is marked by inflammation and damage to the myelin sheath surrounding nerve fibers. Recent studies have highlighted the therapeutic value of exosomes (Exos) obtained from bone marrow mesenchymal stem cells (BMSCs) in MS treatment. These BMSC-Exos contain biologically active molecules that show promising results in preclinical evaluations. The aim of this study was to investigate the mechanism of BMSC-Exos containing miR-23b-3p in both LPS-stimulated BV2 microglia and in experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Exos were isolated from BMSCs, and their effects were evaluated in vitro by co-culturing with BV2 microglia. The interaction between miR-23b-3p and its downstream targets was also explored. The efficacy of BMSC-Exos was further verified in vivo by injecting the Exos into EAE mice. The results showed that BMSC-Exos containing miR-23b-3p reduced microglial pyroptosis in vivo by specifically binding to and suppressing the expression of NEK7. In vivo, BMSC-Exos containing miR-23b-3p alleviated the severity of EAE by decreasing microglial inflammation and pyroptosis via the repression of NEK7. These findings provide new insights into the therapeutic potential of BMSC-Exos containing miR-23b-3p for MS.

Identification of biological pathways and processes regulated by NEK5 in breast epithelial cells via an integrated proteomic approach

Specific members of the Nima-Related Kinase (NEK) family have been linked to cancer development and progression, and a role for NEK5, one of the least studied members, in breast cancer has recently been proposed. However, while NEK5 is known to regulate centrosome separation and mitotic spindle assembly, NEK5 signalling mechanisms and function in this malignancy require further characterization. To this end, we established a model system featuring overexpression of NEK5 in the immortalized breast epithelial cell line MCF-10A. MCF-10A cells overexpressing NEK5 exhibited an increase in clonogenicity under monolayer conditions and enhanced acinar size and abnormal morphology in 3D Matrigel culture. Interestingly, they also exhibited a marked reduction in Src activation and downstream signalling. To interrogate NEK5 signalling and function in an unbiased manner, we applied a variety of MS-based proteomic approaches. Determination of the NEK5 interactome by Bio-ID identified a variety of protein classes including the kinesins KIF2C and KIF22, the mitochondrial proteins TFAM, TFB2M and MFN2, RhoH effectors and the negative regulator of Src, CSK. Characterization of proteins and phosphosites modulated upon NEK5 overexpression by global MS-based (phospho)proteomic profiling revealed impact on the cell cycle, DNA synthesis and repair, Rho GTPase signalling, the microtubule cytoskeleton and hemidesmosome assembly. Overall, the study indicates that NEK5 impacts diverse pathways and processes in breast epithelial cells, and likely plays a multifaceted role in breast cancer development and progression. Video Abstract.

Activation and regulation mechanisms of NOD-like receptors based on structural biology

Innate immunity is a primary defense system against microbial infections. Innate immune pattern recognition receptors (PRRs) play pivotal roles in detection of invading pathogens. When pathogens, such as bacteria and viruses, invade our bodies, their components are recognized by PRRs as pathogen-associated molecular patterns (PAMPs), activating the innate immune system. Cellular components such as DNA and RNA, acting as damage-associated molecular patterns (DAMPs), also activate innate immunity through PRRs under certain conditions. Activation of PRRs triggers inflammatory responses, interferon-mediated antiviral responses, and the activation of acquired immunity. Research on innate immune receptors is progressing rapidly. A variety of these receptors has been identified, and their regulatory mechanisms have been elucidated. Nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) constitute a major family of intracellular PRRs and are involved in not only combating pathogen invasion but also maintaining normal homeostasis. Some NLRs are known to form multi-protein complexes called inflammasomes, a process that ultimately leads to the production of inflammatory cytokines and induces pyroptosis through the proteolytic cascade. The aberrant activation of NLRs has been found to be associated with autoimmune diseases. Therefore, NLRs are considered targets for drug discovery, such as for antiviral drugs, immunostimulants, antiallergic drugs, and autoimmune disease drugs. This review summarizes our recent understanding of the activation and regulation mechanisms of NLRs, with a particular focus on their structural biology. These include NOD2, neuronal apoptosis inhibitory protein (NAIP)/NLRC4, NLR family pyrin domain containing 1 (NLRP1), NLRP3, NLRP6, and NLRP9. NLRs are involved in a variety of diseases, and their detailed activation mechanisms based on structural biology can aid in developing therapeutic agents in the future.

Structural features of the protein kinase domain and targeted binding by small-molecule inhibitors

Protein kinases are key components in cellular signaling pathways as they carry out the phosphorylation of proteins, primarily on Ser, Thr, and Tyr residues. The catalytic activity of protein kinases is regulated, and they can be thought of as molecular switches that are controlled through protein-protein interactions and post-translational modifications. Protein kinases exhibit diverse structural mechanisms of regulation and have been fascinating subjects for structural biologists from the first crystal structure of a protein kinase over 30 years ago, to recent insights into kinase assemblies enabled by the breakthroughs in cryo-EM. Protein kinases are high-priority targets for drug discovery in oncology and other disease settings, and kinase inhibitors have transformed the outcomes of specific groups of patients. Most kinase inhibitors are ATP competitive, deriving potency by occupying the deep hydrophobic pocket at the heart of the kinase domain. Selectivity of inhibitors depends on exploiting differences between the amino acids that line the ATP site and exploring the surrounding pockets that are present in inactive states of the kinase. More recently, allosteric pockets outside the ATP site are being targeted to achieve high selectivity and to overcome resistance to current therapeutics. Here, we review the key regulatory features of the protein kinase family, describe the different types of kinase inhibitors, and highlight examples where the understanding of kinase regulatory mechanisms has gone hand in hand with the development of inhibitors.

Wani T, Batiha GES, Siddique F, Alqarni M, Akintola AA. Deep Learning and Structure-Based Virtual Screening for Drug Discovery against NEK7: A Novel Target for the Treatment of Cancer

NIMA-related kinase7 (NEK7) plays a multifunctional role in cell division and NLRP3 inflammasone activation. A typical expression or any mutation in the genetic makeup of NEK7 leads to the development of cancer malignancies and fatal inflammatory disease, i.e., breast cancer, non-small cell lung cancer, gout, rheumatoid arthritis, and liver cirrhosis. Therefore, NEK7 is a promising target for drug development against various cancer malignancies. The combination of drug repurposing and structure-based virtual screening of large libraries of compounds has dramatically improved the development of anticancer drugs. The current study focused on the virtual screening of 1200 benzene sulphonamide derivatives retrieved from the PubChem database by selecting and docking validation of the crystal structure of NEK7 protein (PDB ID: 2WQN). The compounds library was subjected to virtual screening using Auto Dock Vina. The binding energies of screened compounds were compared to standard Dabrafenib. In particular, compound 762 exhibited excellent binding energy of -42.67 kJ/mol, better than Dabrafenib (-33.89 kJ/mol). Selected drug candidates showed a reactive profile that was comparable to standard Dabrafenib. To characterize the stability of protein-ligand complexes, molecular dynamic simulations were performed, providing insight into the molecular interactions. The NEK7-Dabrafenib complex showed stability throughout the simulated trajectory. In addition, binding affinities, pIC50, and ADMET profiles of drug candidates were predicted using deep learning models. Deep learning models predicted the binding affinity of compound 762 best among all derivatives, which supports the findings of virtual screening. These findings suggest that top hits can serve as potential inhibitors of NEK7. Moreover, it is recommended to explore the inhibitory potential of identified hits compounds through in-vitro and in-vivo approaches.

A Single Amino Acid Residue Defines the Difference in NLRP3 Inflammasome Activation between NEK7 and NEK6

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a critical component of the innate immune system that is activated by microbial infections and cellular stress signals. The molecular mechanism of NLRP3 inflammasome activation remains not fully understood. As an NLRP3-interacting partner, NEK7 has emerged as a critical mediator for NLRP3 inflammasome activation. In contrast to NEK7, NEK6, the closely related member of the NEK family, does not support NLRP3 inflammasome activation. In this study, we show that the mouse NEK7 catalytic domain, which shares high sequence identity with the counterpart of NEK6, mediates its interaction with NLRP3 and inflammasome activation in mouse macrophages. Within their catalytic domains, a single amino acid residue at a corresponding position (R121NEK7, Q132NEK6) differentiates their function in NLRP3 inflammasome activation. Surprisingly, substitution of the glutamine residue to an arginine residue at position 132 confers NEK6 the ability of NLRP3 binding and inflammasome activation in mouse macrophages. Furthermore, our results suggest a structural pocket surrounding the residue R121 of NEK7 that is essential for NLRP3 binding and inflammasome activation.

In Mitosis You Are Not: The NIMA Family of Kinases in Aspergillus, Yeast, and Mammals

The Never in mitosis gene A (NIMA) family of serine/threonine kinases is a diverse group of protein kinases implicated in a wide variety of cellular processes, including cilia regulation, microtubule dynamics, mitotic processes, cell growth, and DNA damage response. The founding member of this family was initially identified in Aspergillus and was found to play important roles in mitosis and cell division. The yeast family has one member each, Fin1p in fission yeast and Kin3p in budding yeast, also with functions in mitotic processes, but, overall, these are poorly studied kinases. The mammalian family, the main focus of this review, consists of 11 members named Nek1 to Nek11. With the exception of a few members, the functions of the mammalian Neks are poorly understood but appear to be quite diverse. Like the prototypical NIMA, many members appear to play important roles in mitosis and meiosis, but their functions in the cell go well beyond these well-established activities. In this review, we explore the roles of fungal and mammalian NIMA kinases and highlight the most recent findings in the field.

Inhibition of the NLRP3 Inflammasome Activation by Manoalide Ameliorates Experimental Autoimmune Encephalomyelitis Pathogenesis

The activation of NLRP3 inflammasome leads to cell pyroptosis and inflammatory cytokines secretion and gets involved in the development of many diseases, such as neuroinflammation and metabolic syndrome, but the drugs targeting NLRP3 are not clinically available for now. Through screening the small molecule library, we found that manoalide is a highly selective small molecule inhibitor of NLRP3. Mechanismly, manoalide inhibited the NLRP3 inflammasome activation by acting downstream of potassium efflux, chloride efflux and mitochondrial dysfunction. Moreover, manoalide blocked the interaction between NEK7 and NLRP3 by covalently binding to Lys 377 of the NLRP3 protein. Treatment of manoalide relieved the pathogenesis of experimental autoimmune encephalomyelitis (EAE) in mice. Thus, our results identify manoalide as a selective and covalent NLRP3 inhibitor and suggest it has the potential for the treatment of NLRP3-associated diseases.

An RRx-001 Analogue With Potent Anti-NLRP3 Inflammasome Activity but Without High-Energy Nitro Functional Groups

NLRP3 inflammasome is involved in the pathology of multiple human inflammatory diseases but there are still no clinically available medications targeting the NLRP3 inflammasome. We have previously identified RRx-001 as a highly selective and potent NLRP3 inhibitor, however, it contains high-energy nitro functional groups and may cause potential processing problems and generates highly toxic oxidants. Here, we show that compound 149-01, an RRx-001 analogue without high-energy nitro functional groups, is a potent, specific and covalent NLRP3 inhibitor. Mechanistically, 149-01 binds directly to cysteine 409 of NLRP3 to block the NEK7-NLRP3 interaction, thereby preventing NLRP3 inflammasome complex assembly and activation. Furthermore, treatment with 149-01 effectively alleviate the severity of several inflammatory diseases in mice, including lipopolysaccharide (LPS)-induced systemic inflammation, monosodium urate crystals (MSU)-induced peritonitis and experimental autoimmune encephalomyelitis (EAE). Thus, our results indicate that 149-01 is a potential lead for developing therapeutic agent for NLRP3-related inflammatory diseases.

Analysis of the effect of NEKs on the prognosis of patients with non-small-cell lung carcinoma based on bioinformatics

NEKs are proteins that are involved in various cell processes and play important roles in the formation and development of cancer. However, few studies have examined the role of NEKs in the development of non-small-cell lung carcinoma (NSCLC). To address this problem, the Oncomine, UALCAN, and the Human Protein Atlas databases were used to analyze differential NEK expression and its clinicopathological parameters, while the Kaplan-Meier, cBioPortal, GEPIA, and DAVID databases were used to analyze survival, gene mutations, similar genes, and biological enrichments. The rate of NEK family gene mutation was high (> 50%) in patients with NSCLC, in which NEK2/4/6/8/ was overexpressed and significantly correlated with tumor stage and nodal metastasis status. In addition, the high expression of NEK2/3mRNA was significantly associated with poor prognosis in patients with NSCLC, while high expression of NEK1/4/6/7/8/9/10/11mRNA was associated with good prognosis. In summary, these results suggest that NEK2/4/6/8 may be a potential prognostic biomarker for the survival of patients with NSCLC.

Crystal Structure of NLRP3 NACHT Domain With an Inhibitor Defines Mechanism of Inflammasome Inhibition

The NLRP3 inflammasome assembles in response to a variety of pathogenic and sterile danger signals, resulting in the production of interleukin-1β and interleukin-18. NLRP3 is a key component of the innate immune system and has been implicated as a driver of a number of acute and chronic diseases. We report the 2.8 Å crystal structure of the NLRP3 NACHT domain in complex with an inhibitor. The structure defines a binding pocket formed by the four subdomains of the NACHT domain, and shows the inhibitor acts as an intramolecular glue, which locks the protein in an inactive conformation. It provides further molecular insight into our understanding of NLRP3 activation, helps to detail the residues involved in subdomain coordination within the NLRP3 NACHT domain, and gives molecular insights into how gain-of-function mutations de-stabilize the inactive conformation of NLRP3. Finally, it suggests stabilizing the auto-inhibited form of the NACHT domain is an effective way to inhibit NLRP3, and will aid the structure-based development of NLRP3 inhibitors for a range of inflammatory diseases.

Erianin: A Direct NLRP3 Inhibitor With Remarkable Anti-Inflammatory Activity

Erianin (Eri) is the extract of Dendrobium chrysotoxum Lindl. The NLRP3 inflammasome is a multiprotein complex that plays key roles in a wide variety of chronic inflammation-driven human diseases. Nevertheless, little is known about the protection of Eri against NLRP3 inflammasome-related diseases. In this study, we demonstrated that Eri inhibited NLRP3 inflammasome activation in vitro and in vivo. Mechanistically, Eri directly interacted with NLRP3, leading to inhibition of NLRP3 inflammasome assembly. Eri associated with the Walker A motif in the NACHT domain and suppressed NLRP3 ATPase activity. In mouse models, Eri had therapeutic effects on peritonitis, gouty arthritis and type 2 diabetes, via NLRP3. More importantly, Eri was active ex vivo for synovial fluid cells and monocytes from patients with IAV infection and gout. Eri may serve as a potential novel therapeutic compound against NLRP3-driven diseases.

Structures and functions of the inflammasome engine

Inflammasomes are molecular machines that carry out inflammatory responses on challenges by pathogens and endogenous dangers. Dysregulation of inflammasome assembly and regulation is associated with numerous human diseases from autoimmunity to cancer. In recent years, significant advances have been made in understanding the mechanism of inflammasome signaling using structural approaches. Here, we review inflammasomes formed by the NLRP1, NLRP3, and NLRC4 sensors, which are well characterized structurally, and discuss the structural and functional diversity among them.

RRx-001 ameliorates inflammatory diseases by acting as a potent covalent NLRP3 inhibitor

The NLRP3 inflammasome plays a crucial role in innate immune-mediated inflammation and contributes to the pathogenesis of multiple autoinflammatory, metabolic and neurodegenerative diseases, but medications targeting the NLRP3 inflammasome are not available for clinical use. RRx-001 is a well-tolerated anticancer agent currently being investigated in phase III clinical trials, but its effects on inflammatory diseases are not known. Here, we show that RRx-001 is a highly selective and potent NLRP3 inhibitor that has strong beneficial effects on NLRP3-driven inflammatory diseases. RRx-001 inhibits the activation of the canonical, noncanonical, and alternative NLRP3 inflammasomes but not the AIM2, NLRC4 or Pyrin inflammasomes. Mechanistically, RRx-001 covalently binds to cysteine 409 of NLRP3 via its bromoacetyl group and therefore blocks the NLRP3-NEK7 interaction, which is critical for the assembly and activation of the NLRP3 inflammasome. More importantly, RRx-001 treatment attenuates the symptoms of lipopolysaccharide (LPS)-induced systemic inflammation, dextran sulfate sodium (DSS)-induced colitis and experimental autoimmune encephalomyelitis (EAE) in mice. Thus, our study identifies RRx-001 as a new potential therapeutic agent for NLRP3-driven diseases.

On Broken Ne(c)ks and Broken DNA: The Role of Human NEKs in the DNA Damage Response

NIMA-related kinases, or NEKs, are a family of Ser/Thr protein kinases involved in cell cycle and mitosis, centrosome disjunction, primary cilia functions, and DNA damage responses among other biological functional contexts in vertebrate cells. In human cells, there are 11 members, termed NEK1 to 11, and the research has mainly focused on exploring the more predominant roles of NEKs in mitosis regulation and cell cycle. A possible important role of NEKs in DNA damage response (DDR) first emerged for NEK1, but recent studies for most NEKs showed participation in DDR. A detailed analysis of the protein interactions, phosphorylation events, and studies of functional aspects of NEKs from the literature led us to propose a more general role of NEKs in DDR. In this review, we express that NEK1 is an activator of ataxia telangiectasia and Rad3-related (ATR), and its activation results in cell cycle arrest, guaranteeing DNA repair while activating specific repair pathways such as homology repair (HR) and DNA double-strand break (DSB) repair. For NEK2, 6, 8, 9, and 11, we found a role downstream of ATR and ataxia telangiectasia mutated (ATM) that results in cell cycle arrest, but details of possible activated repair pathways are still being investigated. NEK4 shows a connection to the regulation of the nonhomologous end-joining (NHEJ) repair of DNA DSBs, through recruitment of DNA-PK to DNA damage foci. NEK5 interacts with topoisomerase IIβ, and its knockdown results in the accumulation of damaged DNA. NEK7 has a regulatory role in the detection of oxidative damage to telomeric DNA. Finally, NEK10 has recently been shown to phosphorylate p53 at Y327, promoting cell cycle arrest after exposure to DNA damaging agents. In summary, this review highlights important discoveries of the ever-growing involvement of NEK kinases in the DDR pathways. A better understanding of these roles may open new diagnostic possibilities or pharmaceutical interventions regarding the chemo-sensitizing inhibition of NEKs in various forms of cancer and other diseases.

Bruton tyrosine kinase deficiency augments NLRP3 inflammasome activation and causes IL-1β-mediated colitis

Bruton tyrosine kinase (BTK) is present in a wide variety of cells and may thus have important non-B cell functions. Here, we explored the function of this kinase in macrophages with studies of its regulation of the NLR family, pyrin domain-containing 3 (NLRP3) inflammasome. We found that bone marrow-derived macrophages (BMDMs) from BTK-deficient mice or monocytes from patients with X-linked agammaglobulinemia (XLA) exhibited increased NLRP3 inflammasome activity; this was also the case for BMDMs exposed to low doses of BTK inhibitors such as ibrutinib and for monocytes from patients with chronic lymphocytic leukemia being treated with ibrutinib. In mechanistic studies, we found that BTK bound to NLRP3 during the priming phase of inflammasome activation and, in doing so, inhibited LPS- and nigericin-induced assembly of the NLRP3 inflammasome during the activation phase of inflammasome activation. This inhibitory effect was caused by BTK inhibition of protein phosphatase 2A-mediated (PP2A-mediated) dephosphorylation of Ser5 in the pyrin domain of NLRP3. Finally, we show that BTK-deficient mice were subject to severe experimental colitis and that such colitis was normalized by administration of anti-IL-β or anakinra, an inhibitor of IL-1β signaling. Together, these studies strongly suggest that BTK functions as a physiologic inhibitor of NLRP3 inflammasome activation and explain why patients with XLA are prone to develop Crohn's disease.

Physiological and Pathological Roles of Mammalian NEK7

NEK7 is the smallest NIMA-related kinase (NEK) in mammals. The pathological and physiological roles of NEK7 have been widely reported in many studies. To date, the major function of NEK7 has been well documented in mitosis and NLRP3 inflammasome activation, but the detailed mechanisms of its regulation remain unclear. This review summarizes current advances in NEK7 research involving mitotic regulation, NLRP3 inflammasome activation, related diseases and potential inhibitors, which may provide new insights into the understanding and therapy of the diseases associated with NEK7, as well as the subsequent studies in the future.

Recent advances in the NEK7-licensed NLRP3 inflammasome activation: Mechanisms, role in diseases and related inhibitors

The nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome is a high-molecular-weight complex mediated by the activation of pattern-recognition receptors (PRRs) seed in innate immunity. Once NLRP3 is activated, the following recruitment of the adapter apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC) and procaspase-1 would be initiated. Cleavage of procaspase-1 into active caspase-1 then leads to the maturation of the precursor forms of interleukin (IL)-1β and IL-18 into biologically active IL-1β and IL-18. The activation of NLRP3 inflammasome is thought to be tightly associated with a regulator never in mitosis A (NIMA)-related kinase 7 (NEK7), apart from other signaling events such as K⁺ efflux and reactive oxygen species (ROS). Plus, the NLRP3 inflammasome has been linked to various metabolic disorders, chronic inflammation and other diseases. In this review, we firstly describe the cellular/molecular mechanisms of the NEK7-licensed NLRP3 inflammasome activation. Then we detail the potential inhibitors that can selectively and effectively modulate either the NEK7-NLRP3 complex itself or the related molecular/cellular events. Finally, we describe some inhibitors as promising therapeutic strategies for diverse diseases driven by NLRP3 inflammasome.

EML4-ALK V3 oncogenic fusion proteins promote microtubule stabilization and accelerated migration through NEK9 and NEK7

EML4-ALK is an oncogenic fusion present in ∼5% of non-small cell lung cancers. However, alternative breakpoints in the EML4 gene lead to distinct variants of EML4-ALK with different patient outcomes. Here, we show that, in cell models, EML4-ALK variant 3 (V3), which is linked to accelerated metastatic spread, causes microtubule stabilization, formation of extended cytoplasmic protrusions and increased cell migration. EML4-ALK V3 also recruits the NEK9 and NEK7 kinases to microtubules via the N-terminal EML4 microtubule-binding region. Overexpression of wild-type EML4, as well as constitutive activation of NEK9, also perturbs cell morphology and accelerates migration in a microtubule-dependent manner that requires the downstream kinase NEK7 but does not require ALK activity. Strikingly, elevated NEK9 expression is associated with reduced progression-free survival in EML4-ALK patients. Hence, we propose that EML4-ALK V3 promotes microtubule stabilization through NEK9 and NEK7, leading to increased cell migration. This represents a novel actionable pathway that could drive metastatic disease progression in EML4-ALK lung cancer.

Nek7 conformational flexibility and inhibitor binding probed through protein engineering of the R-spine

Nek7 is a serine/threonine-protein kinase required for proper spindle formation and cytokinesis. Elevated Nek7 levels have been observed in several cancers, and inhibition of Nek7 might provide a route to the development of cancer therapeutics. To date, no selective and potent Nek7 inhibitors have been identified. Nek7 crystal structures exhibit an improperly formed regulatory-spine (R-spine), characteristic of an inactive kinase. We reasoned that the preference of Nek7 to crystallise in this inactive conformation might hinder attempts to capture Nek7 in complex with Type I inhibitors. Here, we have introduced aromatic residues into the R-spine of Nek7 with the aim to stabilise the active conformation of the kinase through R-spine stacking. The strong R-spine mutant Nek7SRS retained catalytic activity and was crystallised in complex with compound 51, an ATP-competitive inhibitor of Nek2 and Nek7. Subsequently, we obtained the same crystal form for wild-type Nek7WT in apo form and bound to compound 51. The R-spines of the three well-ordered Nek7WT molecules exhibit variable conformations while the R-spines of the Nek7SRS molecules all have the same, partially stacked configuration. Compound 51 bound to Nek2 and Nek7 in similar modes, but differences in the precise orientation of a substituent highlights features that could be exploited in designing inhibitors that are selective for particular Nek family members. Although the SRS mutations are not required to obtain a Nek7-inhibitor structure, we conclude that it is a useful strategy for restraining the conformation of a kinase in order to promote crystallogenesis.

NEK7: a potential therapy target for NLRP3-related diseases

NLRP3 inflammasome plays an essential role in innate immunity, yet the activation mechanism of NLRP3 inflammasome is not clear. In human or animal models, inappropriate NLRP3 inflammasome activation is implicated in many NLRP3-related diseases, such as tumors, inflammatory diseases and autoimmune diseases. Until now, a great number of inhibitors have been used to disturb the related signaling pathways, such as IL-1β blockade, IL-18 blockade and caspase-1 inhibitors. Unfortunately, most of these inhibitors just disturb the signaling pathways after the activation of NLRP3 inflammasome. Inhibitors that directly regulate NLRP3 to abolish the inflammation response may be more effective. NEK7 is a multifunctional kinase affecting centrosome duplication, mitochondrial regulation, intracellular protein transport, DNA repair and mitotic spindle assembly. Researchers have made significant observations on the regulation of gene transcription or protein expression of the NLRP3 inflammasome signaling pathway by NEK7. Those signaling pathways include ROS signaling, potassium efflux, lysosomal destabilization, and NF-κB signaling. Furthermore, NEK7 has been proved to be involved in many NLRP3-related diseases in humans or in animal models. Inhibitors focused on NEK7 may regulate NLRP3 to abolish the inflammation response and NEK7 may be a potential therapeutic target for NLRP3-related diseases.

Checking NEKs: Overcoming a Bottleneck in Human Diseases

In previous years, several kinases, such as phosphoinositide 3-kinase (PI3K), mammalian target of rapamycin (mTOR), and extracellular-signal-regulated kinase (ERK), have been linked to important human diseases, although some kinase families remain neglected in terms of research, hiding their relevance to therapeutic approaches. Here, a review regarding the NEK family is presented, shedding light on important information related to NEKs and human diseases. NEKs are a large group of homologous kinases with related functions and structures that participate in several cellular processes such as the cell cycle, cell division, cilia formation, and the DNA damage response. The review of the literature points to the pivotal participation of NEKs in important human diseases, like different types of cancer, diabetes, ciliopathies and central nervous system related and inflammatory-related diseases. The different known regulatory molecular mechanisms specific to each NEK are also presented, relating to their involvement in different diseases. In addition, important information about NEKs remains to be elucidated and is highlighted in this review, showing the need for other studies and research regarding this kinase family. Therefore, the NEK family represents an important group of kinases with potential applications in the therapy of human diseases.

Emerging roles of the αC-β4 loop in protein kinase structure, function, evolution, and disease

The faithful propagation of cellular signals in most organisms relies on the coordinated functions of a large family of protein kinases that share a conserved catalytic domain. The catalytic domain is a dynamic scaffold that undergoes large conformational changes upon activation. Most of these conformational changes, such as movement of the regulatory αC-helix from an "out" to "in" conformation, hinge on a conserved, but understudied, loop termed the αC-β4 loop, which mediates conserved interactions to tether flexible structural elements to the kinase core. We previously showed that the αC-β4 loop is a unique feature of eukaryotic protein kinases. Here, we review the emerging roles of this loop in kinase structure, function, regulation, and diseases. Through a kinome-wide analysis, we define the boundaries of the loop for the first time and show that sequence and structural variation in the loop correlate with conformational and regulatory variation. Many recurrent disease mutations map to the αC-β4 loop and contribute to drug resistance and abnormal kinase activation by relieving key auto-inhibitory interactions associated with αC-helix and inter-lobe movement. The αC-β4 loop is a hotspot for post-translational modifications, protein-protein interaction, and Hsp90 mediated folding. Our kinome-wide analysis provides insights for hypothesis-driven characterization of understudied kinases and the development of allosteric protein kinase inhibitors.

NEK7 interacts with NLRP3 to modulate the pyroptosis in inflammatory bowel disease via NF-κB signaling

Inflammatory bowel disease (IBD) is one of the most common diseases in the gastrointestinal tract related to aberrant inflammation. Pyroptosis, which is characterized by inflammasome formation, the activation of caspase-1, and the separation of the N- and C-terminals of GSDMD, might be related to IBD pathogenesis. NEK7 is an important component of the NLRP3 inflammasome in macrophages. We attempted to investigate the mechanism of NEK7 interacting with NLRP3 to modulate the pyroptosis in IBD. NEK7 mRNA and protein expression and pyroptosis-associated factors, including Caspase-1 (p45, p20), NLRP3, and GSDMD, were upregulated in IBD tissues. NEK7 knockdown abolish ATP + LPS-induced pyroptosis in vitro and improved DSS-induced chronic colitis in vivo. NEK7 interacted with NLRP3, as revealed by Co-IP and GST pull-down assays, to exert its effects. Moreover, short-term LPS treatment alone induced no significant changes in NEK7 protein level. TLR4/NF-κB signaling in MODE-K cells could be activated by LPS treatment. LPS-induced NEK7 upregulation could be significantly reversed by JSH-23, an inhibitor of p65. Furthermore, LUC and ChIP assays revealed that RELA might activate the transcription of NEK7 via targeting its promoter region. LPS-induced TLR4/NF-κB activation causes an increase in NEK7 expression by RELA binding NEK7 promoter region. In conclusion, NEK7 interacts with NLRP3 to modulate NLRP3 inflammasome activation, therefore modulating the pyroptosis in MODE-K cells and DSS-induced chronic colitis in mice. We provide a novel mechanism of NEK7-NLRP3 interaction affecting IBD via pyroptosis.

Structural Basis of Protein Kinase R Autophosphorylation

The RNA-activated protein kinase, PKR, is a key mediator of the innate immunity response to viral infection. Viral double-stranded RNAs induce PKR dimerization and autophosphorylation. The PKR kinase domain forms a back-to-back dimer. However, intermolecular ( trans) autophosphorylation is not feasible in this arrangement. We have obtained PKR kinase structures that resolves this dilemma. The kinase protomers interact via the known back-to-back interface as well as a front-to-front interface that is formed by exchange of activation segments. Mutational analysis of the front-to-front interface support a functional role in PKR activation. Molecular dynamics simulations reveal that the activation segment is highly dynamic in the front-to-front dimer and can adopt conformations conducive to phosphoryl transfer. We propose a mechanism where back-to-back dimerization induces a conformational change that activates PKR to phosphorylate a "substrate" kinase docked in a front-to-front geometry. This mechanism may be relevant to related kinases that phosphorylate the eukaryotic initiation factor eIF2α.

Structural mechanism for NEK7-licensed activation of NLRP3 inflammasome

The NLRP3 inflammasome can be activated by diverse stimuli, including nigericin, uric acid crystals, amyloid-β fibrils, and extracellular ATP. The mitotic kinase NEK7 licenses NLRP3 inflammasome assembly and activation in the interphase. Here we report a 3.8-Å cryo-electron microscopy structure of inactive human NLRP3 in complex with NEK7. The earring-shaped NLRP3 consists of curved leucine-rich repeat (LRR) and globular NACHT domains, whereas the C-terminal lobe of NEK7 nestles against both NLRP3 domains. Structural recognition between NLRP3 and NEK7 is confirmed by mutagenesis both in vitro and in cells. Modelling of an active NLRP3-NEK7 conformation based on the NLRC4 inflammasome predicts an additional contact between an NLRP3-bound NEK7 and a neighbouring NLRP3. Mutations on this interface abolish the ability of NEK7 or NLRP3 to rescue NLRP3 activation in NEK7^KO or NLRP3^KO cells. Taken together, these data suggest that NEK7 bridges adjacent NLRP3 subunits with bipartite interactions to mediate NLRP3 inflammasome activation.

Comprehensive substrate specificity profiling of the human Nek kinome reveals unexpected signaling outputs

Human NimA-related kinases (Neks) have multiple mitotic and non-mitotic functions, but few substrates are known. We systematically determined the phosphorylation-site motifs for the entire Nek kinase family, except for Nek11. While all Nek kinases strongly select for hydrophobic residues in the −3 position, the family separates into four distinct groups based on specificity for a serine versus threonine phospho-acceptor, and preference for basic or acidic residues in other positions. Unlike Nek1-Nek9, Nek10 is a dual-specificity kinase that efficiently phosphorylates itself and peptide substrates on serine and tyrosine, and its activity is enhanced by tyrosine auto-phosphorylation. Nek10 dual-specificity depends on residues in the HRD+2 and APE-4 positions that are uncommon in either serine/threonine or tyrosine kinases. Finally, we show that the phosphorylation-site motifs for the mitotic kinases Nek6, Nek7 and Nek9 are essentially identical to that of their upstream activator Plk1, suggesting that Nek6/7/9 function as phospho-motif amplifiers of Plk1 signaling.

The Microtubule Regulator NEK7 Coordinates the Wiring of Cortical Parvalbumin Interneurons

Functional networks in the mammalian cerebral cortex rely on the interaction between glutamatergic pyramidal cells and GABAergic interneurons. Both neuronal populations exhibit an extraordinary divergence in morphology and targeting areas, which ultimately dictate their precise function in cortical circuits. How these prominent morphological differences arise during development is not well understood. Here, we conducted a high-throughput screen for genes differentially expressed by pyramidal cells and interneurons during cortical wiring. We found that NEK7, a kinase involved in microtubule polymerization, is mostly expressed in parvalbumin (PV+) interneurons at the time when they establish their connectivity. Functional experiments revealed that NEK7-deficient PV+ interneurons show altered microtubule dynamics, axon growth cone steering and reduced axon length, arbor complexity, and total number of synaptic contacts formed with pyramidal cells. Altogether, our results reveal a molecular mechanism by which the microtubule-associated kinase NEK7 regulates the wiring of PV+ interneurons.

The established and the predicted roles of dynein light chain in the regulation of mitochondrial apoptosis

The mitochondrial pathway of apoptosis is regulated by the interplay between the members of Bcl-2 family. Within this family, BH3-only proteins are the sensors of apoptotic stimuli and can trigger apoptosis either by inhibiting the anti-apoptotic Bcl-2-family proteins or by directly activating the effectors Bax and Bak. An expanding body of research suggests that a number of non-Bcl-2 proteins can also interact with Bcl-2 proteins and contribute to the decision of cell fate. Dynein light chain (LC8, DYNLL or DLC), a hub protein and a dimerizing engine has been proposed to regulate the pro-apoptotic activity of two BH3-only proteins, Bim and Bmf. Our recent work has provided insight into the mechanisms through which DLC1 (DYNLL1) modulates Bim activity. Here we discuss the present day understanding of Bim-DLC interaction and endeavor to evaluate this interaction in the light of information from studies of DLC with other binding partners.

Oridonin is a covalent NLRP3 inhibitor with strong anti-inflammasome activity

Oridonin (Ori) is the major active ingredient of the traditional Chinese medicinal herb Rabdosia rubescens and has anti-inflammatory activity, but the target of Ori remains unknown. NLRP3 is a central component of NLRP3 inflammasome and has been involved in a wide variety of chronic inflammation-driven human diseases. Here, we show that Ori is a specific and covalent inhibitor for NLRP3 inflammasome. Ori forms a covalent bond with the cysteine 279 of NLRP3 in NACHT domain to block the interaction between NLRP3 and NEK7, thereby inhibiting NLRP3 inflammasome assembly and activation. Importantly, Ori has both preventive or therapeutic effects on mouse models of peritonitis, gouty arthritis and type 2 diabetes, via inhibition of NLRP3 activation. Our results thus identify NLRP3 as the direct target of Ori for mediating Ori's anti-inflammatory activity. Ori could serve as a lead for developing new therapeutics against NLRP3-driven diseases.

NEK7 regulates dendrite morphogenesis in neurons via Eg5-dependent microtubule stabilization

Organization of microtubules into ordered arrays is best understood in mitotic systems, but remains poorly characterized in postmitotic cells such as neurons. By analyzing the cycling cell microtubule cytoskeleton proteome through expression profiling and targeted RNAi screening for candidates with roles in neurons, we have identified the mitotic kinase NEK7. We show that NEK7 regulates dendrite morphogenesis in vitro and in vivo. NEK7 kinase activity is required for dendrite growth and branching, as well as spine formation and morphology. NEK7 regulates these processes in part through phosphorylation of the kinesin Eg5/KIF11, promoting its accumulation on microtubules in distal dendrites. Here, Eg5 limits retrograde microtubule polymerization, which is inhibitory to dendrite growth and branching. Eg5 exerts this effect through microtubule stabilization, independent of its motor activity. This work establishes NEK7 as a general regulator of the microtubule cytoskeleton, controlling essential processes in both mitotic cells and postmitotic neurons.

NEK7 is a kinase known for its role in mitotic spindle assembly, driving centrosome separation in prophase through regulation of the kinesin Eg5. Here, the authors show that NEK7 and Eg5 also control dendrite morphogenesis in postmitotic neurons.

Mitotic Regulation by NEK Kinase Networks

Genetic studies in yeast and Drosophila led to identification of cyclin-dependent kinases (CDKs), Polo-like kinases (PLKs) and Aurora kinases as essential regulators of mitosis. These enzymes have since been found in the majority of eukaryotes and their cell cycle-related functions characterized in great detail. However, genetic studies in another fungal species, Aspergillus nidulans, identified a distinct family of protein kinases, the NEKs, that are also widely conserved and have key roles in the cell cycle, but which remain less well studied. Nevertheless, it is now clear that multiple NEK family members act in networks to regulate specific events of mitosis, including centrosome separation, spindle assembly and cytokinesis. Here, we describe our current understanding of how the NEK kinases contribute to these processes, particularly through targeted phosphorylation of proteins associated with the microtubule cytoskeleton. We also present the latest findings on molecular events that control the activation state of the NEKs and how these are revealing novel modes of enzymatic regulation relevant not only to other kinases but also to pathological mechanisms of disease.

Hsp72 and Nek6 Cooperate to Cluster Amplified Centrosomes in Cancer Cells

Cancer cells frequently possess extra amplified centrosomes clustered into two poles whose pseudo-bipolar spindles exhibit reduced fidelity of chromosome segregation and promote genetic instability. Inhibition of centrosome clustering triggers multipolar spindle formation and mitotic catastrophe, offering an attractive therapeutic approach to selectively kill cells with amplified centrosomes. However, mechanisms of centrosome clustering remain poorly understood. Here, we identify a new pathway that acts through NIMA-related kinase 6 (Nek6) and Hsp72 to promote centrosome clustering. Nek6, as well as its upstream activators polo-like kinase 1 and Aurora-A, targeted Hsp72 to the poles of cells with amplified centrosomes. Unlike some centrosome declustering agents, blocking Hsp72 or Nek6 function did not induce formation of acentrosomal poles, meaning that multipolar spindles were observable only in cells with amplified centrosomes. Inhibition of Hsp72 in acute lymphoblastic leukemia cells resulted in increased multipolar spindle frequency that correlated with centrosome amplification, while loss of Hsp72 or Nek6 function in noncancer-derived cells disturbs neither spindle formation nor mitotic progression. Hence, the Nek6-Hsp72 module represents a novel actionable pathway for selective targeting of cancer cells with amplified centrosomes. Cancer Res; 77(18); 4785-96. ©2017 AACR.

Recent insights into the molecular mechanisms of the NLRP3 inflammasome activation

Inflammasomes are high-molecular-weight protein complexes that are formed in the cytosolic compartment in response to danger- or pathogen-associated molecular patterns. These complexes enable activation of an inflammatory protease caspase-1, leading to a cell death process called pyroptosis and to proteolytic cleavage and release of pro-inflammatory cytokines interleukin (IL)-1β and IL-18. Along with caspase-1, inflammasome components include an adaptor protein, ASC, and a sensor protein, which triggers the inflammasome assembly in response to a danger signal. The inflammasome sensor proteins are pattern recognition receptors belonging either to the NOD-like receptor (NLR) or to the AIM2-like receptor family. While the molecular agonists that induce inflammasome formation by AIM2 and by several other NLRs have been identified, it is not well understood how the NLR family member NLRP3 is activated. Given that NLRP3 activation is relevant to a range of human pathological conditions, significant attempts are being made to elucidate the molecular mechanism of this process. In this review, we summarize the current knowledge on the molecular events that lead to activation of the NLRP3 inflammasome in response to a range of K (+) efflux-inducing danger signals. We also comment on the reported involvement of cytosolic Ca (2+) fluxes on NLRP3 activation. We outline the recent advances in research on the physiological and pharmacological mechanisms of regulation of NLRP3 responses, and we point to several open questions regarding the current model of NLRP3 activation.