The camKK2/camKIV relay is an essential regulator of hepatic cancer

Development and Characterization of Novel Molecular Probes for Ca2+/Calmodulin-Dependent Protein Kinase Kinase, Derived from STO-609

Ca²⁺/calmodulin-dependent protein kinase kinase (CaMKK) activates particular multifunctional kinases, including CaMKI, CaMKIV, and 5'AMP-activated protein kinase (AMPK), resulting in the regulation of various Ca²⁺-dependent cellular processes, including neuronal, metabolic, and pathophysiological pathways. We developed and characterized a novel pan-CaMKK inhibitor, TIM-063 (2-hydroxy-3-nitro-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one) derived from STO-609 (7H-benzimidazo[2,1-a]benz[de]isoquinoline-7-one-3-carboxylic acid), and an inactive analogue (TIM-062) as molecular probes for the analysis of CaMKK-mediated cellular responses. Unlike STO-609, TIM-063 had an inhibitory activity against CaMKK isoforms (CaMKKα and CaMKKβ) with a similar potency (K_i = 0.35 μM for CaMKKα, and K_i = 0.2 μM for CaMKKβ) in vitro. Two TIM-063 analogues lacking a nitro group (TIM-062) or a hydroxy group (TIM-064) completely impaired CaMKK inhibitory activities, indicating that both substituents are necessary for the CaMKK inhibitory activity of TIM-063. Enzymatic analysis revealed that TIM-063 is an ATP-competitive inhibitor that directly targets the catalytic domain of CaMKK, similar to STO-609. TIM-063 suppressed the ionomycin-induced phosphorylation of exogenously expressed CaMKI, CaMKIV, and endogenous AMPKα in HeLa cells with an IC₅₀ of ∼0.3 μM, and it suppressed CaMKK isoform-mediated CaMKIV phosphorylation in transfected COS-7 cells. Thus, TIM-063, but not the inactive analogue (TIM-062), displayed cell permeability and the ability to inhibit CaMKK activity in cells. Taken together, these results indicate that TIM-063 could be a useful tool for the precise analysis of CaMKK-mediated signaling pathways and may be a promising lead compound for the development of therapeutic agents for the treatment of CaMKK-related diseases.

In Depth Analysis of Kinase Cross Screening Data to Identify CAMKK2 Inhibitory Scaffolds

The calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2) activates CAMK1, CAMK4, AMPK, and AKT, leading to numerous physiological responses. The deregulation of CAMKK2 is linked to several diseases, suggesting the utility of CAMKK2 inhibitors for oncological, metabolic and inflammatory indications. In this work, we demonstrate that STO-609, frequently described as a selective inhibitor for CAMKK2, potently inhibits a significant number of other kinases. Through an analysis of literature and public databases, we have identified other potent CAMKK2 inhibitors and verified their activities in differential scanning fluorimetry and enzyme inhibition assays. These inhibitors are potential starting points for the development of selective CAMKK2 inhibitors and will lead to tools that delineate the roles of this kinase in disease biology.

Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes

Objective

Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4.

Methods

Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD).

Results

Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca²⁺/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD.

Conclusions

Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease.

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The GLP-1R agonist exendin-4 suppressed lipid accumulation by upregulating ABCA1 expression in hepatocytes.

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Exendin-4 regulated the expression and transcription of hepatic ABCA1 via the CaMKK/CaMKIV/PREB pathway.

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Overexpression of PREB or exendin-4 protected mouse liver from fatty liver by upregulation of ABCA1.

MiR-129-5p inhibits liver cancer growth by targeting calcium calmodulin-dependent protein kinase IV (CAMK4)

This study was designed to investigate the mechanism by which miR-129-5p affects the biological function of liver cancer cells. The expression levels of miR-129–5p in liver cancer tissues and cells were, respectively, determined. Crystal violet staining and flow cytometry were used to detect cell proliferation and apoptosis. Wound healing assay and transwell assay were performed to test cell migration and invasion. The target gene of miR-129–5p was analyzed and verified by bioinformatics analysis and luciferase reporter assay. Tumorigenicity assays in nude mice were used to test the antitumor ability of calcium calmodulin-dependent protein kinase IV (CAMK4). miR-129–5p was found to be underexpressed in hepatocellular cancer tissues and cells and also to inhibit liver cells proliferation, migration, and invasion and promote apoptosis. CAMK4 was a direct target for miR-129–5p and was lowly expressed in liver cancer tissues and cells. CAMK4 was also found to inhibit liver cells proliferation, migration and invasion, and promote apoptosis. CAMK4 might exert an antitumor effect by inhibiting the activation of mitogen-activated protein kinase (MAPK). MiR-129–5p was a tumor suppressor with low expression in liver cancer tissues and cells. CAMK4, which is a direct target gene of miR-129–5p, could inhibit tumor by inhibiting the activation of MAPK signaling pathway.

CaMKK2 Signaling in Metabolism and Skeletal Disease: a New Axis with Therapeutic Potential

PURPOSE OF REVIEW

Age and metabolic disorders result in the accumulation of advanced glycation endproducts (AGEs), oxidative stress, and inflammation, which cumulatively cause a decline in skeletal health. Bone becomes increasingly vulnerable to fractures and its regenerative capacity diminishes under such conditions. With a rapidly aging population in the USA and the global increase in diabetes, efficacious, multi-dimensional therapies that can treat or prevent skeletal diseases associated with metabolic dysfunction and inflammatory disorders are acutely needed.

RECENT FINDINGS

Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a key regulator of nutrient intake, glucose metabolism, insulin production, and adipogenesis. Recent studies suggest a pivotal role for CaMKK2 in bone metabolism, fracture healing, and inflammation. Aside from rekindling previous concepts of CaMKK2 as a potent regulator of whole-body energy homeostasis, this review emphasizes CaMKK2 as a potential therapeutic target to treat skeletal diseases that underlie metabolic conditions and inflammation.

Deranged hepatocyte intracellular Ca2+ homeostasis and the progression of non-alcoholic fatty liver disease to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths in men, and the sixth in women. Non-alcoholic fatty liver disease (NAFLD) is now one of the major risk factors for HCC. NAFLD, which involves the accumulation of excess lipid in cytoplasmic lipid droplets in hepatocytes, can progress to non-alcoholic steatosis, fibrosis, and HCC. Changes in intracellular Ca²⁺ constitute important signaling pathways for the regulation of lipid and carbohydrate metabolism in normal hepatocytes. Recent studies of steatotic hepatocytes have identified lipid-induced changes in intracellular Ca²⁺, and have provided evidence that altered Ca²⁺ signaling exacerbates lipid accumulation and may promote HCC. The aims of this review are to summarise current knowledge of the lipid-induced changes in hepatocyte Ca²⁺ homeostasis, to comment on the mechanisms involved, and discuss the pathways leading from altered Ca²⁺ homeostasis to enhanced lipid accumulation and the potential promotion of HCC. In steatotic hepatocytes, lipid inhibits store-operated Ca²⁺ entry and SERCA2b, and activates Ca²⁺ efflux from the endoplasmic reticulum (ER) and its transfer to mitochondria. These changes are associated with changes in Ca²⁺ concentrations in the ER (decreased), cytoplasmic space (increased) and mitochondria (likely increased). They lead to: inhibition of lipolysis, lipid autophagy, lipid oxidation, and lipid secretion; activation of lipogenesis; increased lipid; ER stress, generation of reactive oxygen species (ROS), activation of Ca²⁺/calmodulin-dependent kinases and activation of transcription factor Nrf2. These all can potentially mediate the transition of NAFLD to HCC. It is concluded that lipid-induced changes in hepatocyte Ca²⁺ homeostasis are important in the initiation and progression of HCC. Further research is desirable to better understand the cause and effect relationships, the time courses and mechanisms involved, and the potential of Ca²⁺ transporters, channels, and binding proteins as targets for pharmacological intervention.

Bioinformatics analysis identifies potential chemoresistance-associated genes across multiple types of cancer

Despite the fact that studies have revealed mechanisms underlying tumor chemoresistance, the functions of numerous potential chemoresistance-associated genes have yet to be elucidated. A bioinformatics analysis was conducted to screen differentially expressed genes (DEGs) across four types of chemoresistant tumors and functional enrichment analysis was used to examine the biological significance of these genes. Furthermore, a gene network was constructed using weighted gene co-expression network analysis to identify hub genes. A total of 6,015, 2,074, 2,141 and 954 differentially expressed genes were identified in estrogen receptor-negative breast cancer, ovarian cancer, rectal cancer and gastric cancer, respectively; however, only five of these DEGs were dysregulated in all four types of cancer. Functional enrichment analysis of the DEGs suggested that genomic stability and immune response are crucial determinants of tumor chemoresistance. In addition, 14, 8, 6 and 1 co-expressed gene modules were identified in estrogen receptor-negative breast cancer, ovarian cancer, rectal cancer and gastric cancer, respectively, and protein-protein interaction networks were created. The analysis identified only calcium-calmodulin-dependent protein kinase kinase 2, erythropoietin receptor, mitochondrial poly(A) RNA polymerase, α-parvin, and zinc finger and BTB domain-containing protein 44 to be dysregulated in all four cancer types, indicating varying mechanisms of chemoresistance in different tumor types. Furthermore, our analysis suggests that type I collagen α1, fibroblast growth factor 14 and major histocompatibility complex, class II, DR β1 potentially serve key roles in the development of chemoresistance. In conclusion, the present study proposes a simple and effective strategy for identifying genes involved in chemoresistance and predicting their potential functional roles, which may guide subsequent experimental studies.

CaMKK2 in myeloid cells is a key regulator of the immune-suppressive microenvironment in breast cancer

Tumor-associated myeloid cells regulate tumor growth and metastasis, and their accumulation is a negative prognostic factor for breast cancer. Here we find calcium/calmodulin-dependent kinase kinase (CaMKK2) to be highly expressed within intratumoral myeloid cells in mouse models of breast cancer, and demonstrate that its inhibition within myeloid cells suppresses tumor growth by increasing intratumoral accumulation of effector CD8+ T cells and immune-stimulatory myeloid subsets. Tumor-associated macrophages (TAMs) isolated from Camkk2-/- mice expressed higher levels of chemokines involved in the recruitment of effector T cells compared to WT. Similarly, in vitro generated Camkk2-/- macrophages recruit more T cells, and have a reduced capability to suppress T cell proliferation, compared to WT. Treatment with CaMKK2 inhibitors blocks tumor growth in a CD8+ T cell-dependent manner, and facilitates a favorable reprogramming of the immune cell microenvironment. These data, credential CaMKK2 as a myeloid-selective checkpoint, the inhibition of which may have utility in the immunotherapy of breast cancer.

Hesperidin-CAMKIV interaction and its impact on cell proliferation and apoptosis in the human hepatic carcinoma and neuroblastoma cells

Calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a key regulatory molecule of cell signaling, and thereby controls its growth and proliferation, including expression of certain genes. The overexpression of CAMKIV is directly associated with the development of different types of cancers. Hesperidin is abundantly found in citrus fruits and exhibits wide range of pharmacological activities including anti-inflammatory, antibacterial and anticancerous effects. We have investigated binding mechanism of hesperidin with the CAMKIV using molecular docking methods followed by fluorescence quenching and isothermal titration calorimetric assays. An appreciable binding affinity of hesperidin was observed with CAMKIV during fluorescence quenching and isothermal titration calorimetric studies. Efficacy of hesperidin to inhibit the growth of human hepatic carcinoma (HepG2) and neuroblastoma (SH-SY5Y) cancer cell lines were investigated. Hesperidin has significantly reduced the proliferation of HepG2 and SH-SY5Y cells and induces apoptosis by activating the caspase-3-dependent intrinsic pathway through the upregulation of proapoptotic Bax protein. Hesperidin treatment reduces the mitochondrial membrane potential of HepG2 and SH-SY5Y cells. All these observations clearly anticipated hesperidin a potent inhibitor of CAMKIV which may be further exploited a newer therapeutic approach for the management of different cancer types.

Peptide V3 Inhibits the Growth of Human Hepatocellular Carcinoma by Inhibiting the Ras/Raf/MEK/ERK Signaling Pathway

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths. Peptide V3 has shown anti-angiogenic and anti-tumor effects on S180 and H22 xenografts in nude mice. However, the detailed mechanism of action of peptide V3 has not yet been fully elucidated. In the present study, the effects of peptide V3 on the growth of human HCC cells were examined both in vitro and in vivo. Our results showed that peptide V3 inhibited the proliferation, viability, migration, and invasion of human HCC cells. However, no obvious effect was observed in HL-7702 cells. Peptide V3 increased the apoptosis and decreased the protein levels of H-RAS, phospho (p)-RAF, p-MEK, and p-extracellular signal-regulated protein kinase (ERK) in human HCC cells. Peptide V3 suppressed the growth of human HCC xenografts by down-regulating angiogenesis and up-regulating apoptosis. In conclusion, peptide V3 could inhibit the growth of human HCC by inhibiting the Ras/Raf/MEK/ERK signaling pathway. Novel peptides and modification strategies could be designed and applied for the treatment of different types of cancer.

The Kinome of Human Alveolar Type II and Basal Cells, and Its Reprogramming in Lung Cancer

The discovery of mutant tyrosine kinases as oncogenic drivers of lung adenocarcinomas has changed the basic understanding of lung cancer development and therapy. Yet, expressed kinases (kinome) in lung cancer progenitor cells, as well as whether kinase expression and the overall kinome changes or is reprogrammed upon transformation, is incompletely understood. We hypothesized that the kinome differs between lung cancer progenitor cells, alveolar type II cells (ATII), and basal cells (BC) and that their respective kinomes undergo distinct lineage-specific reprogramming to adenocarcinomas and squamous cell carcinomas upon transformation. We performed RNA sequencing on freshly isolated human ATII, BC, and lung cancer cell lines to define the kinome in nontransformed cells and transformed cells. Our studies identified a unique kinome for ATII and BC and changes in their kinome upon transformation to their respective carcinomas.

Serum cytokine levels as predictive biomarkers of benefit from ipilimumab in small cell lung cancer

Background. Immunotherapy has shown efficacy in small cell lung cancer (SCLC), but only a subset of patients benefits. Surrogate biomarkers are urgently needed. Our aim was to evaluate serum Th1, Th2, and proinflammatory cytokines in two cohorts of SCLC patients before and during treatment with chemotherapy with or without ipilimumab and to correlate them with survival. Patients and methods. Two cohorts of SCLC patients were studied: patients treated with chemotherapy (n = 47), and patients treated with chemotherapy plus ipilimumab (n = 37). Baseline, on-treatment and after-treatment serum samples were evaluated for the presence of IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IFN-gamma, TNF-alpha, GM-CSF, and Mip-1alpha using a Luminex assay. Differential changes in cytokines between cohorts were analyzed. Associations between cytokine levels and their changes with overall survival were evaluated. Results. Patients treated with ipilimumab showed a global increase of all cytokines after treatment initiation. A high level of IL-8 at baseline was associated with worse prognosis regardless of treatment. Baseline increased IL-2 levels predicted sensitivity to ipilimumab, while high IL-6 and TNF-alpha predicted resistance. An on-treatment increase in IL-4 levels in patients treated with immune-chemotherapy was associated with a better overall survival. Conclusions. The addition of ipilimumab to standard chemotherapy in SCLC modulates the serum levels of cytokines. Baseline levels and their change over time relate to overall survival. Blood-based biomarkers are convenient for patients, and our results support prospective validation of cytokines as predictive biomarkers for ipilimumab in SCLC.

DNA methylation signature of smoking in lung cancer is enriched for exposure signatures in newborn and adult blood

Smoking impacts DNA methylation genome-wide in blood of newborns from maternal smoking during pregnancy and adults from personal smoking. We compared smoking-related DNA methylation in lung adenocarcinoma (61 never smokers, 91 current smokers, and 238 former smokers) quantified with the Illumina450k BeadArray in The Cancer Genome Atlas with published large consortium meta-analyses of newborn and adult blood. We assessed whether CpG sites related to smoking in blood from newborns and adults were enriched in the lung adenocarcinoma methylation signal. Testing CpGs differentially methylated by smoke exposure, we identified 296 in lung adenocarcinoma meeting a P < 10-4 cutoff, while previous meta-analyses identified 3,042 in newborn blood, and 8,898 in adult blood meeting the same P < 10-4 cutoff. Lung signals were highly enriched for those seen in newborn (24 overlapping CpGs, Penrichment = 1.2 × 10-18) and adult blood (66 overlapping CpGs, Penrichment = 1.2 × 10-48). The 105 genes annotated to CpGs differentially methylated in lung tumors, but not blood, were enriched for RNA processing ontologies. Some epigenetic alterations associated with cigarette smoke exposure are tissue specific, but others are common across tissues. These findings support the value of blood-based methylation biomarkers for assessing exposure effects in target tissues.

The Multi-Functional Calcium/Calmodulin Stimulated Protein Kinase (CaMK) Family: Emerging Targets for Anti-Cancer Therapeutic Intervention

The importance of Ca²⁺ signalling in key events of cancer cell function and tumour progression, such as proliferation, migration, invasion and survival, has recently begun to be appreciated. Many cellular Ca²⁺-stimulated signalling cascades utilise the intermediate, calmodulin (CaM). The Ca²⁺/CaM complex binds and activates a variety of enzymes, including members of the multifunctional Ca²⁺/calmodulin-stimulated protein kinase (CaMK) family. These enzymes control a broad range of cancer-related functions in a multitude of tumour types. Herein, we explore the cancer-related functions of these kinases and discuss their potential as targets for therapeutic intervention.

Loss of Ca2+/Calmodulin Dependent Protein Kinase Kinase 2 Leads to Aberrant Transferrin Phosphorylation and Trafficking: A Potential Biomarker for Alzheimer's Disease

Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a serine/threonine kinase that is activated following an increase in the intracellular Ca²⁺ concentration and activates multiple signaling cascades that control physiologically important neuronal processes. CaMKK2 has been implicated in schizophrenia, bipolar disease, neurodegeneration, and cancer. Using isoelectric focusing (IEF) and mass spectrometry-based proteomic analysis, it was found that knockdown (KD) of CaMKK2 in cultured adult primary dorsal root ganglion (DRG) neurons resulted in the reduction of transferrin (TF) phosphorylation at multiple functionally relevant residues which corresponded to loss of an acidic fraction (pH~3-4) of TF. In vitro studies using CRISPR/Cas9 based CaMKK2 knockout (KO) HEK293 and HepG2 cells lines validated previous findings and revealed that loss of CaMKK2 interfered with TF trafficking and turnover. TF is an iron transporter glycoprotein. Abnormal accumulation of iron and/or deregulated Ca²⁺ homeostasis leads to neurodegeneration in Alzheimer's disease (AD). Therefore, it was hypothesized that aberrant CaMKK2 in AD may lead to aberrant phosphorylated transferrin (P-TF: pH~3-4 fraction) which may serve as a hallmark biomarker for AD. A significant reduction of P-TF in the brain and serum of CaMKK2 KO mice and a triple-transgenic mouse model of AD (3xTg-AD) supported this hypothesis. In addition, analysis of early (< 65 years) and late-stage (>65 years) postmortem human AD cerebrospinal fluid (CSF) and serum samples revealed that aberrant P-TF (pH~3-4 fraction) profile was associated with both early and late-stage AD compared to age-matched controls. This indicates P-TF (pH~3-4 fraction) profile may be useful as a minimally invasive biomarker for AD. In addition, this study provides a link between aberrant CaMKK2 with TF trafficking and turnover which provides a novel insight into the neurodegeneration process.

High throughput screening, docking, and molecular dynamics studies to identify potential inhibitors of human calcium/calmodulin-dependent protein kinase IV

Calcium/calmodulin-dependent protein kinase IV (CAMKIV) is associated with many diseases including cancer and neurodegenerative disorders and thus being considered as a potential drug target. Here, we have employed the knowledge of three-dimensional structure of CAMKIV to identify new inhibitors for possible therapeutic intervention. We have employed virtual high throughput screening of 12,500 natural compounds of Zinc database to screen the best possible inhibitors of CAMKIV. Subsequently, 40 compounds which showed significant docking scores (-11.6 to -10.0 kcal/mol) were selected and further filtered through Lipinski rule and drug likeness parameter to get best inhibitors of CAMKIV. Docking results are indicating that ligands are binding to the hydrophobic cavity of the kinase domain of CAMKIV and forming a significant number of non-covalent interactions. Four compounds, ZINC02098378, ZINC12866674, ZINC04293413, and ZINC13403020, showing excellent binding affinity and drug likeness were subjected to molecular dynamics simulation to evaluate their mechanism of interaction and stability of protein-ligand complex. Our observations clearly suggesting that these selected ligands may be further employed for therapeutic intervention to address CAMKIV associated diseases. Communicated by Ramaswamy H. Sarma.

CAMKK2 Promotes Prostate Cancer Independently of AMPK via Increased Lipogenesis

: New targets are required for treating prostate cancer, particularly castrate-resistant disease. Previous studies reported that calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2) expression is increased in human prostate cancer. Here, we show that Camkk2 deletion or pharmacologic inhibition protects against prostate cancer development in a preclinical mouse model that lacks expression of prostate-specific Pten. In contrast, deletion of AMP-activated protein kinase (Ampk) β1 resulted in earlier onset of adenocarcinoma development. These findings suggest for the first time that Camkk2 and Ampk have opposing effects in prostate cancer progression. Loss of CAMKK2 in vivo or in human prostate cancer cells reduced the expression of two key lipogenic enzymes, acetyl-CoA carboxylase and fatty acid synthase. This reduction was mediated via a posttranscriptional mechanism, potentially involving a decrease in protein translation. Moreover, either deletion of CAMKK2 or activation of AMPK reduced cell growth in human prostate cancer cells by inhibiting de novo lipogenesis. Activation of AMPK in a panel of human prostate cancer cells inhibited cell proliferation, migration, and invasion as well as androgen-receptor signaling. These findings demonstrate that CAMKK2 and AMPK have opposing effects on lipogenesis, providing a potential mechanism for their contrasting effects on prostate cancer progression in vivo. They also suggest that inhibition of CAMKK2 combined with activation of AMPK would offer an efficacious therapeutic strategy in treatment of prostate cancer. SIGNIFICANCE: These findings show that CAMKK2 and its downstream target AMPK have opposing effects on prostate cancer development and raise the possibility of a new combined therapeutic approach that inhibits CAMKK2 and activates AMPK.

Concurrent regulation of LKB1 and CaMKK2 in the activation of AMPK in castrate-resistant prostate cancer by a well-defined polyherbal mixture with anticancer properties

BACKGROUND

Zyflamend, a blend of herbal extracts, effectively inhibits tumor growth using preclinical models of castrate-resistant prostate cancer mediated in part by 5'-adenosine monophosphate-activated protein kinase (AMPK), a master energy sensor of the cell. Clinically, treatment with Zyflamend and/or metformin (activators of AMPK) had benefits in castrate-resistant prostate cancer patients who no longer responded to treatment. Two predominant upstream kinases are known to activate AMPK: liver kinase B1 (LKB1), a tumor suppressor, and calcium-calmodulin kinase kinase-2 (CaMKK2), a tumor promotor over-expressed in many cancers. The objective was to interrogate how Zyflamend activates AMPK by determining the roles of LKB1 and CaMKK2.

METHODS

AMPK activation was determined in CWR22Rv1 cells treated with a variety of inhibitors of LKB1 and CaMKK2 in the presence and absence of Zyflamend, and in LKB1-null HeLa cells that constitutively express CaMKK2, following transfection with wild type LKB1 or catalytically-dead mutants. Upstream regulation by Zyflamend of LKB1 and CaMKK2 was investigated targeting protein kinase C-zeta (PKCζ) and death-associated protein kinase (DAPK), respectively.

RESULTS

Zyflamend's activation of AMPK appears to be LKB1 dependent, while simultaneously inhibiting CaMKK2 activity. Zyflamend failed to rescue the activation of AMPK in the presence of pharmacological and molecular inhibitors of LKB1, an effect not observed in the presence of inhibitors of CaMKK2. Using LKB1-null and catalytically-dead LKB1-transfected HeLa cells that constitutively express CaMKK2, ionomycin (activator of CaMKK2) increased phosphorylation of AMPK, but Zyflamend only had an effect in cells transfected with wild type LKB1. Zyflamend appears to inhibit CaMKK2 by DAPK-mediated phosphorylation of CaMKK2 at Ser511, an effect prevented by a DAPK inhibitor. Alternatively, Zyflamend mediates LKB1 activation via increased phosphorylation of PKCζ, where it induced translocation of PKCζ and LKB1 to their respective active compartments in HeLa cells following treatment. Altering the catalytic activity of LKB1 did not alter this translocation.

DISCUSSION

Zyflamend's activation of AMPK is mediated by LKB1, possibly via PKCζ, but independent of CaMKK2 by a mechanism that appears to involve DAPK.

CONCLUSIONS

Therefore, this is the first evidence that natural products simultaneously and antithetically regulate upstream kinases, known to be involved in cancer, via the activation of AMPK.

Lipid Nanoparticle Formulations for Enhanced Co-delivery of siRNA and mRNA

Although mRNA and siRNA have significant therapeutic potential, their simultaneous delivery has not been previously explored. To facilitate the treatment of diseases associated with aberrant gene upregulation and downregulation, we sought to co-formulate siRNA and mRNA in a single lipidoid nanoparticle (LNP) formulation. We accommodated the distinct molecular characteristics of mRNA and siRNA in a formulation consisting of an ionizable and biodegradable amine-containing lipidoid, cholesterol, DSPC, DOPE, and PEG-lipid. Surprisingly, the co-formulation of siRNA and mRNA in the same LNP enhanced the efficacy of both drugs in vitro and in vivo. Compared to LNPs encapsulating siRNA only, co-formulated LNPs improved Factor VII gene silencing in mice from 44 to 87% at an siRNA dose of 0.03 mg/kg. Co-formulation also improved mRNA delivery, as a 0.5 mg/kg dose of mRNA co-formulated with siRNA induced three times the luciferase protein expression compared to when siRNA was not included. As not all gene therapy applications require both RNA drugs, we sought to extend the benefit of co-formulated LNPs to formulations encapsulating only a single type of RNA. We accomplished this by substituting the "helper" RNA with a negatively charged polymer, polystyrenesulfonate (PSS). LNPs containing PSS mediated the same level of protein silencing or expression as standard LNPs using 2-3-fold less RNA. For example, LNPs formulated with and without PSS induced 50% Factor VII silencing at siRNA doses of 0.01 and 0.03 mg/kg, respectively. Together, these studies demonstrate potent co-delivery of siRNA and mRNA and show that inclusion of a negatively charged "helper polymer" enhances the efficacy of LNP delivery systems.

1,2,6-Thiadiazinones as Novel Narrow Spectrum Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 (CaMKK2) Inhibitors

We demonstrate for the first time that 4H-1,2,6-thiadiazin-4-one (TDZ) can function as a chemotype for the design of ATP-competitive kinase inhibitors. Using insights from a co-crystal structure of a 3,5-bis(arylamino)-4H-1,2,6-thiadiazin-4-one bound to calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2), several analogues were identified with micromolar activity through targeted displacement of bound water molecules in the active site. Since the TDZ analogues showed reduced promiscuity compared to their 2,4-dianilinopyrimidine counter parts, they represent starting points for development of highly selective kinase inhibitors.

Androgen Receptor-CaMKK2 Axis in Prostate Cancer and Bone Microenvironment

The skeletal system is of paramount importance in advanced stage prostate cancer (PCa) as it is the preferred site of metastasis. Complex mechanisms are employed sequentially by PCa cells to home to and colonize the bone. Bone-resident PCa cells then recruit osteoblasts (OBs), osteoclasts (OCs), and macrophages within the niche into entities that promote cancer cell growth and survival. Since PCa is heavily reliant on androgens for growth and survival, androgen-deprivation therapy (ADT) is the standard of care for advanced disease. Although it significantly improves survival rates, ADT detrimentally affects bone health and significantly increases the risk of fractures. Moreover, whereas the majority patients with advanced PCa respond favorably to androgen deprivation, most experience a relapse of the disease to a hormone-refractory form within 1-2 years of ADT. The tumor adapts to surviving under low testosterone conditions by selecting for mutations in the androgen receptor (AR) that constitutively activate it. Thus, AR signaling remains active in PCa cells and aids in its survival under low levels of circulating androgens and additionally allows the cancer cells to manipulate the bone microenvironment to fuel its growth. Hence, AR and its downstream effectors are attractive targets for therapeutic interventions against PCa. Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2), was recently identified as a key downstream target of AR in coordinating PCa cell growth, survival, and migration. Additionally, this multifunctional serine/threonine protein kinase is a critical mediator of bone remodeling and macrophage function, thus emerging as an attractive therapeutic target downstream of AR in controlling metastatic PCa and preventing ADT-induced bone loss. Here, we discuss the role played by AR-CaMKK2 signaling axis in PCa survival, metabolism, cell growth, and migration as well as the cell-intrinsic roles of CaMKK2 in OBs, OCs, and macrophages within the bone microenvironment.

Calcium Promotes Human Gastric Cancer via a Novel Coupling of Calcium-Sensing Receptor and TRPV4 Channel

Although dietary calcium intake has long been recommended for disease prevention, the influence of calcium in development of cancer in the upper gastrointestinal tract has not been explored. Here, we assess the roles of calcium and calcium-sensing receptor (CaSR) in gastric cancer development. CaSR expression was enhanced in gastric cancer specimens, which positively correlated with serum calcium concentrations, tumor progression, poor survival, and male gender in gastric cancer patients. CaSR and transient receptor potential cation channel subfamily V member 4 (TRPV4) were colocalized in gastric cancer cells, and CaSR activation evoked TRPV4-mediated Ca²⁺ entry. Both CaSR and TRPV4 were involved in Ca²⁺-induced proliferation, migration, and invasion of gastric cancer cells through a Ca²⁺/AKT/β-catenin relay, which occurred only in gastric cancer cells or normal cells overexpressing CaSR. Tumor growth and metastasis of gastric cancer depended on CaSR in nude mice. Overall, our findings indicate that calcium may enhance expression and function of CaSR to potentially promote gastric cancer, and that targeting the novel CaSR/TRPV4/Ca²⁺ pathway might serve as preventive or therapeutic strategies for gastric cancer. Cancer Res; 77(23); 6499-512. ©2017 AACR.

Pharmacological inhibition of CaMKK2 with the selective antagonist STO-609 regresses NAFLD

Binding of calcium to its intracellular receptor calmodulin (CaM) activates a family of Ca²⁺/CaM-dependent protein kinases. CaMKK2 (Ca²⁺/CaM-dependent protein kinase kinase 2) is a central member of this kinase family as it controls the actions of a CaMK cascade involving CaMKI, CaMKIV or AMPK. CaMKK2 controls insulin signaling, metabolic homeostasis, inflammation and cancer cell growth highlighting its potential as a therapeutic target for a variety of diseases. STO-609 is a selective, small molecule inhibitor of CaMKK2. Although STO-609 has been used extensively in vitro and in cells to characterize and define new mechanistic functions of CaMKK2, only a few studies have reported the in vivo use of STO-609. We synthesized functional STO-609 and assessed its pharmacological properties through in vitro (kinase assay), ex vivo (human liver microsomes) and in vivo (mouse) model systems. We describe the metabolic processing of STO-609, its toxicity, pharmacokinetics and bioavailability in a variety of mouse tissues. Utilizing these data, we show STO-609 treatment to inhibit CaMKK2 function confers protection against non-alcoholic fatty liver disease. These data provide a valuable resource by establishing criteria for use of STO-609 to inhibit the in vivo functions of CaMKK2 and demonstrate its utility for treating metabolically-related hepatic disease.

Evidence of vanillin binding to CAMKIV explains the anti-cancer mechanism in human hepatic carcinoma and neuroblastoma cells

Human calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a member of Ser/Thr kinase family, and is associated with different types of cancer and neurodegenerative diseases. Vanillin is a natural compound, a primary component of the extract of the vanilla bean which possesses varieties of pharmacological features including anti-oxidant, anti-inflammatory, anti-bacterial and anti-tumor. Here, we have investigated the binding mechanism and affinity of vanillin to the CAMKIV which is being considered as a potential drug target for cancer and neurodegenerative diseases. We found that vanillin binds strongly to the active site cavity of CAMKIV and stabilized by a large number of non-covalent interactions. We explored the utility of vanillin as anti-cancer agent and found that it inhibits the proliferation of human hepatocyte carcinoma (HepG2) and neuroblastoma (SH-SY5Y) cells in a dose-dependent manner. Furthermore, vanillin treatment resulted into the significant reduction in the mitochondrial membrane depolarization and ROS production that eventually leads to apoptosis in HepG2 and SH-SY5Y cancer cells. These findings may offer a novel therapeutic approach by targeting the CAMKIV using natural product and its derivative with a minimal side effect.

Pharmacological stimulation of nuclear factor (erythroid-derived 2)-like 2 translation activates antioxidant responses

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the master regulator of the antioxidant response, and its function is tightly regulated at the transcriptional, translational, and post-translational levels. It is well-known that Nrf2 is regulated at the protein level by proteasomal degradation via Kelch-like ECH-associated protein 1 (Keap1), but how Nrf2 is regulated at the translational level is less clear. Here, we show that pharmacological stimulation increases Nrf2 levels by overcoming basal translational repression. We developed a novel reporter assay that enabled identification of natural compounds that induce Nrf2 translation by a mechanism independent of Keap1-mediated degradation. Apigenin, resveratrol, and piceatannol all induced Nrf2 translation. More importantly, the pharmacologically induced Nrf2 overcomes Keap1 regulation, translocates to the nucleus, and activates the antioxidant response. We conclude that translational regulation controls physiological levels of Nrf2, and this can be modulated by apigenin, resveratrol, and piceatannol. Also, targeting this mechanism with novel compounds could provide new insights into prevention and treatment of multiple diseases in which oxidative stress plays a significant role.

Glucose-dependent regulation of pregnane X receptor is modulated by AMP-activated protein kinase

Pregnane X receptor (PXR) is a xenobiotic receptor that regulates the detoxification and clearance of drugs and foreign compounds from the liver. There has been mounting evidence of crosstalk between the drug metabolism pathway and the energy metabolism pathway, but little is known about this cross-regulation. To further delineate the energy metabolism and drug metabolism crosstalk in this study, we exposed HepG2 cells to varying glucose concentrations. We observed that PXR activity was induced under high-glucose conditions. This finding is consistent with previous clinical reports of increased drug clearance in patients with untreated diabetes. We demonstrated that AMP-activated protein kinase (AMPK) modulates PXR transcriptional activity and that pharmacologically manipulated AMPK activation exhibits an inverse relation to PXR activity. Activation of AMPK was shown to downregulate PXR activity and, consistent with that, potentiate the response of cells to the drug. Taken together, our results delineate a hitherto unreported axis of regulation that involves the energy status of the cell, PXR regulation, and drug sensitivity.

Impact of Genetic Variation on Human CaMKK2 Regulation by Ca2+-Calmodulin and Multisite Phosphorylation

The Ca²⁺-calmodulin dependent protein kinase kinase-2 (CaMKK2) is a key regulator of neuronal function and whole-body energy metabolism. Elevated CaMKK2 activity is strongly associated with prostate and hepatic cancers, whereas reduced CaMKK2 activity has been linked to schizophrenia and bipolar disease in humans. Here we report the functional effects of nine rare-variant point mutations that were detected in large-scale human genetic studies and cancer tissues, all of which occur close to two regulatory phosphorylation sites and the catalytic site on human CaMKK2. Four mutations (G87R, R139W, R142W and E268K) cause a marked decrease in Ca²⁺-independent autonomous activity, however S137L and P138S mutants displayed increased autonomous and Ca²⁺-CaM stimulated activities. Furthermore, the G87R mutant is defective in Thr85-autophosphorylation dependent autonomous activity, whereas the A329T mutation rendered CaMKK2 virtually insensitive to Ca²⁺-CaM stimulation. The G87R and R139W mutants behave as dominant-negative inhibitors of CaMKK2 signaling in cells as they block phosphorylation of the downstream substrate AMP-activated protein kinase (AMPK) in response to ionomycin. Our study provides insight into functionally disruptive, rare-variant mutations in human CaMKK2, which have the potential to influence risk and burden of disease associated with aberrant CaMKK2 activity in human populations carrying these variants.

A spatiotemporal hypothesis for the regulation, role, and targeting of AMPK in prostate cancer

The 5'-AMP-activated protein kinase (AMPK) is a master regulator of cellular homeostasis. Despite AMPK's known function in physiology, its role in pathological processes such as prostate cancer is enigmatic. However, emerging evidence is now beginning to decode the paradoxical role of AMPK in cancer and, therefore, inform clinicians if - and how - AMPK could be therapeutically targeted. Spatiotemporal regulation of AMPK complexes could be one of the mechanisms that governs this kinase's role in cancer. We hypothesize that different upstream stimuli will activate select subcellular AMPK complexes. This hypothesis is supported by the distinct subcellular locations of the various AMPK subunits. Each of these unique AMPK complexes regulates discrete downstream processes that can be tumour suppressive or oncogenic. AMPK's final biological output is then determined by the weighted net function of these downstream signalling events, influenced by additional prostate-specific signalling.

Design, synthesis, and biological evaluation of pyrimidine derivatives as potential inhibitors of human calcium/calmodulin-dependent protein kinase IV

Calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a multifunctional Ser/Thr kinase, associated with cerebral hypoxia, cancer, and neurodegenerative diseases. Here, we report design, synthesis, and biological evaluation of seven pyrimidine-substituted novel inhibitors of CAMKIV. We successfully synthesized and extensively characterized (ESI-MS, ¹ H NMR, and ¹³ C NMR studies) seven compounds that are showing appreciable binding affinity to the CAMKIV. Molecular docking and fluorescence binding studies revealed that compound 1 is showing very high binding free energy (ΔG = -11.52 kcal/mol) and binding affinity (K = 9.2 × 10¹⁰ m^-1 ) to the CAMKIV. We further performed MTT assay to check the cytotoxicity and anticancer activity of these compounds. An appreciable IC₅₀ (39 μm) value of compound 1 was observed on human hepatoma cell line and nontoxic till the 400 μm on human embryonic kidney cells. To ensure anticancer activity of all these compounds, we further performed propidium iodide assay to evaluate cell viability and DNA content during the cell cycle. We found that compound 1 is again showing a better anticancer activity on both human hepatoma and human embryonic kidney cell lines.

CaMKK2 Suppresses Muscle Regeneration through the Inhibition of Myoblast Proliferation and Differentiation

Skeletal muscle has a major role in locomotion and muscle disorders are associated with poor regenerative efficiency. Therefore, a deeper understanding of muscle regeneration is needed to provide a new insight for new therapies. CaMKK2 plays a role in the calcium/calmodulin-dependent kinase cascade; however, its role in skeletal muscle remains unknown. Here, we found that CaMKK2 expression levels were altered under physiological and pathological conditions including postnatal myogensis, freeze or cardiotoxin-induced muscle regeneration, and Duchenne muscular dystrophy. Overexpression of CaMKK2 suppressed C2C12 myoblast proliferation and differentiation, while inhibition of CaMKK2 had opposite effect. We also found that CaMKK2 is able to activate AMPK in C2C12 myocytes. Inhibition of AMPK could attenuate the effect of CaMKK2 overexpression, while AMPK agonist could abrogate the effect of CaMKK2 knockdown on C2C12 cell differentiation and proliferation. These results suggest that CaMKK2 functions as an AMPK kinase in muscle cells and AMPK mediates the effect of CaMKK2 on myoblast proliferation and differentiation. Our data also indicate that CaMKK2 might inhibit myoblast proliferation through AMPK-mediated cell cycle arrest by inducing cdc2-Tyr15 phosphorylation and repress differentiation through affecting PGC1α transcription. Lastly, we show that overexpressing CaMKK2 in the muscle of mice via electroporation impaired the muscle regeneration during freeze-induced injury, indicating that CaMKK2 could serve as a potential target to treat patients with muscle injury or myopathies. Together, our study reveals a new role for CaMKK2 as a negative regulator of myoblast differentiation and proliferation and sheds new light on the molecular regulation of muscle regeneration.

The Ca(2+)/Calmodulin/CaMKK2 Axis: Nature's Metabolic CaMshaft

Calcium (Ca(2+)) is an essential ligand that binds its primary intracellular receptor calmodulin (CaM) to trigger a variety of downstream processes and pathways. Central to the actions of Ca(2+)/CaM is the activation of a highly conserved Ca(2+)/CaM kinase (CaMK) cascade that amplifies Ca(2+) signals through a series of subsequent phosphorylation events. Proper regulation of Ca(2+) flux is necessary for whole-body metabolism and disruption of Ca(2+) homeostasis has been linked to various metabolic diseases. Here we provide a synthesis of recent advances that highlight the roles of the Ca(2+)/CaMK axis in key metabolic tissues. An appreciation of this information is critical to understanding the mechanisms by which Ca(2+)/CaM-dependent signaling contributes to metabolic homeostasis and disease.

Gene expression profile analysis in response to α1,2-fucosyl transferase (FUT1) gene transfection in epithelial ovarian carcinoma cells

The aim of this study was to identify differentially expressed genes (DEGs) in response to α1,2-fucosyl transferase (FUT1) gene transfection in epithelial ovarian cancer cells. Human whole-genome oligonucleotide microarrays were used to determine whether gene expression profile may differentiate the epithelial ovarian cell line Caov-3 transfected with FUT1 from the empty plasmid-transfected cells. Quantitative real-time PCR and immunohistochemical staining validated the microarray results. Gene expression profile identified 215 DEGs according to the selection criteria, in which 122 genes were upregulated and 93 genes were downregulated. Gene Ontology (GO) and canonical pathway enrichment analysis were applied, and we found that these DEGs are involved in BioCarta mammalian target of rapamycin (mTOR) pathway, BioCarta eukaryotic translation initiation factor 4 (EIF4) pathway, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in cancer. Interaction network analysis predicted genes participating in the regulatory connection. Highly differential expression of TRIM46, PCF11, BCL6, PTEN, and FUT1 genes was validated by quantitative real-time PCR in two cell line samples. Finally, BCL6 and Lewis Y antigen were validated at the protein level by immunohistochemistry in 103 paraffin-embedded ovarian cancer tissues. The identification of genes in response to FUT1 may provide a theoretical basis for the investigations of the molecular mechanism of ovarian cancer.

CAMKK2, Regulated by Promoter Methylation, is a Prognostic Marker in Diffuse Gliomas

AIMS

To explore the expression, methylation pattern, the prognostic value, and the biological consequences of CAMKK2 in gliomas.

METHODS

The expression and methylation pattern of CAMKK2 was inferred and validated from mRNA expression profile (N = 866) and methylation profile (N = 426) of glioma tissue samples, and independent samples were used for further validation by IHC and pyrosequencing. To explore the function of CAMKK2 in gliomas, in vitro studies, colony formation assays and migration and invasion assays were performed.

RESULTS

We found the upregulation of CAMKK2 in high-grade glioma samples was associated with promoter hypomethylation. An elevated expression of CAMKK2 was associated with worse prognosis. By in vitro assays, we demonstrated that CAMKK2 could promote cell migration, invasion, and proliferation.

CONCLUSIONS

The expression level of CAMKK2 could be regulated by promoter methylation. CAMKK2 serves as a prognostic marker in gliomas and could be a potential therapeutic target in gliomas.

Research Resource: Roles for Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 (CaMKK2) in Systems Metabolism

A number of epidemiological studies have implicated calcium (Ca(2+)) signaling as a major factor in obesity that contributes to aberrant systems metabolism. Somewhat paradoxically, obesity correlates with decreased circulating Ca(2+) levels, leading to increased release of intracellular Ca(2+) stores from the endoplasmic reticulum. These findings suggest that insulin resistance associated with the obese state is linked to activation of canonical Ca(2+) signaling pathways. Mechanistically, increased intracellular Ca(2+) binds calmodulin (CaM) to activate a set of Ca(2+)/CaM-dependent protein kinases. In this research resource, we explore the metabolic functions and implications of Ca(2+)/CaM-dependent protein kinase kinase 2 (CaMKK2) as a metabolic effector of Ca(2+)/CaM action. We reveal the importance of CaMKK2 for gating insulin release from pancreatic β-cells while concomitantly influencing the sensitivity of insulin-responsive tissues. To provide a better understanding of the metabolic impact of CaMKK2 loss, we performed targeted metabolomic analyses of key metabolic byproducts of glucose, fatty acid, and amino acid metabolism in mice null for CaMKK2. We quantified amino acids and acyl carnitines in 3 insulin-sensitive tissues (liver, skeletal muscle, plasma) isolated from CaMKK2(-/-) mice and their wild-type littermates under conditions of dietary stress (low-fat diet, normal chow, high-fat diet, and fasting), thereby unveiling unique metabolic functions of CaMKK2. Our findings highlight CaMKK2 as a molecular rheostat for insulin action and emphasize the importance of Ca(2+)/CaM/CaMKK2 in regulation of whole-body metabolism. These findings reveal that CaMKK2 may be an attractive therapeutic target for combatting comorbidities associated with perturbed insulin signaling.

Effect of pH on the structure, function, and stability of human calcium/calmodulin-dependent protein kinase IV: combined spectroscopic and MD simulation studies

Human calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a member of Ser/Thr protein kinase family. It is regulated by the calcium-calmodulin dependent signal through a secondary messenger, Ca(2+), which leads to the activation of its autoinhibited form. The over-expression and mutation in CAMKIV as well as change in Ca(2+) concentration is often associated with numerous neurodegenerative diseases and cancers. We have successfully cloned, expressed, and purified a functionally active kinase domain of human CAMKIV. To observe the effect of different pH conditions on the structural and functional properties of CAMKIV, we have used spectroscopic techniques such as circular diachroism (CD) absorbance and fluorescence. We have observed that within the pH range 5.0-11.5, CAMKIV maintained both its secondary and tertiary structures, along with its function, whereas significant aggregation was observed at acidic pH (2.0-4.5). We have also performed ATPase activity assays under different pH conditions and found a significant correlation between the structure and enzymatic activities of CAMKIV. In-silico validations were further carried out by modeling the 3-dimensional structure of CAMKIV and then subjecting it to molecular dynamics (MD) simulations to understand its conformational behavior in explicit water conditions. A strong correlation between spectroscopic observations and the output of molecular dynamics simulation was observed for CAMKIV.

Structure guided design of potential inhibitors of human calcium-calmodulin dependent protein kinase IV containing pyrimidine scaffold

Calmodulin dependent protein kinase IV (CAMKIV) belongs to the serine/threonine protein kinase family and considered as an encouraging target for the development of novel anticancer agents. The interaction and binding behavior of three designed inhibitors of human CAMKIV, containing pyrimidine scaffold, was monitored by in vitro fluorescence titration and molecular docking calculations under physiological condition. In silico docking studies were performed to screen several compounds containing pyrimidine scaffold against CAMKIV. Molecular docking calculation predicted the binding of these ligands in active-site cavity of the CAMKIV structure correlating such interactions with a probable inhibition mechanism. Finally, three active pyrimidine substituted compounds (molecules 1-3) have been successfully synthesized and characterized by (1)H and (13)C NMR. Molecule 3 is showing very high binding-affinity for the CAMKIV, with a binding constant of 2.2×10(8), M(-1) (±0.20). All three compounds are nontoxic to HEK293 cells up to 50 μM. The cell proliferation inhibition study showed that the molecule 3 has lowest IC50 value (46±1.08 μM). The theoretical and experimental observations are significantly correlated. This study reveals some important observations to generate an improved pyrimidine based compound that holds promise as a therapeutic agent for the treatment of cancer and neurodegenerative diseases.