DYRK1B mutations associated with metabolic syndrome impair the chaperone-dependent maturation of the kinase domain

Abdominal Obesity-Metabolic Syndrome 3 Misclassified as Type 1 Diabetes Mellitus

Age is no longer the most important differentiating feature between type 1 and type 2 diabetes, as obesity and metabolic syndrome are on the rise in the pediatric population. Here we present a case of a 30-year-old male individual initially diagnosed with uncontrolled type 1 diabetes mellitus (T1DM) since the age of 15, and treatment with high insulin doses has been unsuccessful. He was later identified as having abdominal obesity-metabolic syndrome 3 (AOMS3) based on strong family history and the presence of insulin resistance features. AOMS3 is characterized by early-onset coronary artery disease, central obesity, hypertension, and diabetes. Early detection of this condition is crucial to implement timely interventions and preventing the onset of complications.

Functional characterization of two DYRK1B variants causative of AOMS3

BACKGROUND

Two new missense variants (K68Q and R252H) of the protein kinase DYRK1B were recently reported to cause a monogenetic form of metabolic syndrome with autosomal dominant inheritance (AOMS3).

RESULTS

Our in vitro functional analysis reveals that neither of these substitutions eliminates or enhances the catalytic activity of DYRK1B. DYRK1B-K68Q displays reduced nuclear translocation.

CONCLUSION

The pathogenicity of DYRK1B variants does not necessarily correlate with the gain or loss of catalytic activity, but can be due to altered non-enzymatic characteristics such as subcellular localization.

Mirk/Dyrk1B Kinase Inhibitors in Targeted Cancer Therapy

During the last years, there has been an increased effort in the discovery of selective and potent kinase inhibitors for targeted cancer therapy. Kinase inhibitors exhibit less toxicity compared to conventional chemotherapy, and several have entered the market. Mirk/Dyrk1B kinase is a promising pharmacological target in cancer since it is overexpressed in many tumors, and its overexpression is correlated with patients' poor prognosis. Mirk/Dyrk1B acts as a negative cell cycle regulator, maintaining the survival of quiescent cancer cells and conferring their resistance to chemotherapies. Many studies have demonstrated the valuable therapeutic effect of Mirk/Dyrk1B inhibitors in cancer cell lines, mouse xenografts, and patient-derived 3D-organoids, providing a perspective for entering clinical trials. Since the majority of Mirk/Dyrk1B inhibitors target the highly conserved ATP-binding site, they exhibit off-target effects with other kinases, especially with the highly similar Dyrk1A. In this review, apart from summarizing the data establishing Dyrk1B as a therapeutic target in cancer, we highlight the most potent Mirk/Dyrk1B inhibitors recently reported. We also discuss the limitations and perspectives for the structure-based design of Mirk/Dyrk1B potent and highly selective inhibitors based on the accumulated structural data of Dyrk1A and the recent crystal structure of Dyrk1B with AZ191 inhibitor.

Pathogenic, Total Loss-of-Function DYRK1B Variants Cause Monogenic Obesity Associated With Type 2 Diabetes

OBJECTIVE

Rare variants in DYRK1B have been described in some patients with central obesity, type 2 diabetes, and early-onset coronary disease. Owing to the limited number of conducted studies, the broader impact of DYRK1B variants on a larger scale has yet to be investigated.

RESEARCH DESIGN AND METHODS

DYRK1B was sequenced in 9,353 participants from a case-control study for obesity and type 2 diabetes. Each DYRK1B variant was functionally assessed in vitro. Variant pathogenicity was determined using criteria from the American College of Medical Genetics and Genomics (ACMG). The effect of pathogenic or likely pathogenic (P/LP) variants on metabolic traits was assessed using adjusted mixed-effects score tests.

RESULTS

Sixty-five rare, heterozygous DYRK1B variants were identified and were not associated with obesity or type 2 diabetes. Following functional analyses, 20 P/LP variants were pinpointed, including 6 variants that exhibited a fully inhibitory effect (P/LP-null) on DYRK1B activity. P/LP and P/LP-null DYRK1B variants were associated with increased BMI and obesity risk; however, the impact was notably more pronounced for the P/LP-null variants (effect of 8.0 ± 3.2 and odds ratio of 7.9 [95% CI 1.2-155]). Furthermore, P/LP-null variants were associated with higher fasting glucose and type 2 diabetes risk (effect of 2.9 ± 1.0 and odds ratio of 4.8 [95% CI 0.85-37]), while P/LP variants had no effect on glucose homeostasis.

CONCLUSIONS

P/LP, total loss-of-function DYRK1B variants cause monogenic obesity associated with type 2 diabetes. This study underscores the significance of conducting functional assessments in order to accurately ascertain the tangible effects of P/LP DYRK1B variants.

Systems biology approach to identify biomarkers and therapeutic targets for colorectal cancer

Background

Colorectal cancer (CRC), is the third most prevalent cancer across the globe, and is often detected at advanced stage. Late diagnosis of CRC, leave the chemotherapy and radiotherapy as the main options for the possible treatment of the disease which are associated with severe side effects. In the present study, we seek to explore CRC gene expression data using a systems biology framework to identify potential biomarkers and therapeutic targets for earlier diagnosis and treatment of the disease.

Methods

The expression data was retrieved from the gene expression omnibus (GEO). Differential gene expression analysis was conducted using R/Bioconductor package. The PPI network was reconstructed by the STRING. Cystoscope and Gephi software packages were used for visualization and centrality analysis of the PPI network. Clustering analysis of the PPI network was carried out using k-mean algorithm. Gene-set enrichment based on Gene Ontology (GO) and KEGG pathway databases was carried out to identify the biological functions and pathways associated with gene groups. Prognostic value of the selected identified hub genes was examined by survival analysis, using GEPIA.

Results

A total of 848 differentially expressed genes were identified. Centrality analysis of the PPI network resulted in identification of 99 hubs genes. Clustering analysis dissected the PPI network into seven interactive modules. While several DEGs and the central genes in each module have already reported to contribute to CRC progression, survival analysis confirmed high expression of central genes, CCNA2, CD44, and ACAN contribute to poor prognosis of CRC patients. In addition, high expression of TUBA8, AMPD3, TRPC1, ARHGAP6, JPH3, DYRK1A and ACTA1 was found to associate with decreased survival rate.

Conclusion

Our results identified several genes with high centrality in PPI network that contribute to progression of CRC. The fact that several of the identified genes have already been reported to be relevant to diagnosis and treatment of CRC, other highlighted genes with limited literature information may hold potential to be explored in the context of CRC biomarker and drug target discovery.

Mirk/Dyrk1B controls ventral spinal cord development via Shh pathway

Cross-talk between Mirk/Dyrk1B kinase and Sonic hedgehog (Shh)/Gli pathway affects physiology and pathology. Here, we reveal a novel role for Dyrk1B in regulating ventral progenitor and neuron subtypes in the embryonic chick spinal cord (SC) via the Shh pathway. Using in ovo gain-and-loss-of-function approaches at E2, we report that Dyrk1B affects the proliferation and differentiation of neuronal progenitors at E4 and impacts on apoptosis specifically in the motor neuron (MN) domain. Especially, Dyrk1B overexpression decreases the numbers of ventral progenitors, MNs, and V2a interneurons, while the pharmacological inhibition of endogenous Dyrk1B kinase activity by AZ191 administration increases the numbers of ventral progenitors and MNs. Mechanistically, Dyrk1B overexpression suppresses Shh, Gli2 and Gli3 mRNA levels, while conversely, Shh, Gli2 and Gli3 transcription is increased in the presence of Dyrk1B inhibitor AZ191 or Smoothened agonist SAG. Most importantly, in phenotype rescue experiments, SAG restores the Dyrk1B-mediated dysregulation of ventral progenitors. Further at E6, Dyrk1B affects selectively the medial lateral motor neuron column (LMCm), consistent with the expression of Shh in this region. Collectively, these observations reveal a novel regulatory function of Dyrk1B kinase in suppressing the Shh/Gli pathway and thus affecting ventral subtypes in the developing spinal cord. These data render Dyrk1B a possible therapeutic target for motor neuron diseases.

DnaK promotes autophosphorylation of DYRK1A and its family kinases in Escherichia coli-based cell-free protein expression

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is one of the drug target kinases involved in neurological disorders. DYRK1A phosphorylates substrate proteins related to disease progression in an intermolecular manner. Meanwhile, DYRK1A intramolecularly phosphorylates its own residues on key segments during folding process, which is required for its activation and stabilization. To reproduce the autophosphorylation in vitro, DYRK1A was expressed in Escherichia coli-based cell-free protein synthesis system. Although this system was useful for investigating autophosphorylation of serine residue at position 97 (Ser97) in DYRK1A, only a small fraction of the synthesized protein was successfully autophosphorylated. In this study, we found that the addition of DnaK, a bacterial HSP70 chaperone, to cell-free expression of DYRK1A promoted its Ser97 autophosphorylation. Structure prediction with AlphaFold2 indicates that Ser97 forms a hydrogen bond within an α-helix structure, indicating a possibility that DnaK unfolds the α-helix and maintains the structure around Ser97 in a conformation susceptible to phosphorylation. In addition, DnaK promoted phosphorylation of DYRK1B and HIPK2, but not DYRK2 and DYRK4, suggesting a sequence selectivity in the action of DnaK. This study provides a facile method for promoting autophosphorylation of DYRK family kinases in cell-free protein expression.

Identification of FAM53C as a cytosolic-anchoring inhibitory binding protein of the kinase DYRK1A

The protein kinase DYRK1A encoded in human chromosome 21 is the major contributor to the multiple symptoms observed in Down syndrome patients. In addition, DYRK1A malfunction is associated with various other neurodevelopmental disorders such as autism spectrum disorder. Here, we identified FAM53C with no hitherto known biological function as a novel suppressive binding partner of DYRK1A. FAM53C is bound to the catalytic protein kinase domain of DYRK1A, whereas DCAF7/WDR68, the major DYRK1A-binding protein, binds to the N-terminal domain of DYRK1A. The binding of FAM53C inhibited autophosphorylation activity of DYRK1A and its kinase activity to an exogenous substrate, MAPT/Tau. FAM53C did not bind directly to DCAF7/WDR68, whereas DYRK1A tethered FAM53C and DCAF7/WDR68 by binding concurrently to both of them, forming a tri-protein complex. DYRK1A possesses an NLS and accumulates in the nucleus when overexpressed in cells. Co-expression of FAM53C induced cytoplasmic re-localization of DYRK1A, revealing the cytoplasmic anchoring function of FAM53C to DYRK1A. Moreover, the binding of FAM53C to DYRK1A suppressed the DYRK1A-dependent nuclear localization of DCAF7/WDR68. All the results show that FAM53C binds to DYRK1A, suppresses its kinase activity, and anchors it in the cytoplasm. In addition, FAM53C is bound to the DYRK1A-related kinase DYRK1B with an Hsp90/Cdc37-independent manner. The results explain for the first time why endogenous DYRK1A is distributed in the cytoplasm in normal brain tissue. FAM53C-dependent regulation of the kinase activity and intracellular localization of DYRK1A may play a significant role in gene expression regulation caused by normal and aberrant levels of DYRK1A.

DYRK1B inhibition exerts senolytic effects on endothelial cells and rescues endothelial dysfunctions

Aging is the major risk factor for chronic disease development. Cellular senescence is a key mechanism that triggers or contributes to age-related phenotypes and pathologies. The endothelium, a single layer of cells lining the inner surface of a blood vessel, is a critical interface between blood and all tissues. Many studies report a link between endothelial cell senescence, inflammation, and diabetic vascular diseases. Here we identify, using combined advanced AI and machine learning, the Dual Specificity Tyrosine Phosphorylation Regulated Kinase 1B (DYRK1B) protein as a possible senolytic target for senescent endothelial cells. We demonstrate that upon induction of senescence in vitro DYRK1B expression is increased in endothelial cells and localized at adherens junctions where it impairs their proper organization and functions. DYRK1B knock-down or inhibition restores endothelial barrier properties and collective behavior. DYRK1B is therefore a possible target to counteract diabetes-associated vascular diseases linked to endothelial cell senescence.

Inhibition of DYRK1B suppresses inflammation in allergic contact dermatitis model and Th1/Th17 immune response

Allergic contact dermatitis (ACD) is a type IV hypersensitivity mainly mediated by Th1/Th17 immune response. Topical corticosteroid is currently the first-line treatment for allergic contact dermatitis (ACD) and systemic administration of immunosuppressive drugs are used in patients with severe disseminated cases. However, increased risk of adverse effects has limited their use. Thus, the development of a novel immunosuppressant for ACD with low toxicity is a challenging issue. In this study, we began our study by using a murine contact hypersensitivity (CHS) model of ACD to examine the immunosuppressive effects of DYRK1B inhibition. We found that mice treated with a selective DYRK1B inhibitor show reduced ear inflammation. In addition, a significant reduction of Th1 and Th17 cells in the regional lymph node upon DYRK1B inhibition was observed by FACS analysis. Studies in vitro further revealed that DYRK1B inhibitor does not only suppressed Th1 and Th17 differentiation, but also promotes regulatory T cells (Treg) differentiation. Mechanistically, FOXO1 signaling was enhanced due to the suppression of FOXO1Ser329 phosphorylation in the presence of DYRK1B inhibitor. Therefore, these findings suggest that DYRK1B regulates CD4 T cell differentiation through FOXO1 phosphorylation and DYRK1B inhibitor has a potential as a novel agent for treatment of ACD.

A Bioinformatics Evaluation of the Role of Dual-Specificity Tyrosine-Regulated Kinases in Colorectal Cancer

Simple Summary

The dual-specificity tyrosine-regulated kinase (DYRK) family has been implicated in various diseases, including cancer. However, its role in colorectal cancer has not been elucidated. In this research, we used publicly available web-based tools to investigate DYRKs status in colorectal cancer. Our results showed that among DYRKs, only DYRK1A was upregulated significantly in late tumor stages, and it is associated with poor prognosis for colorectal cancer patients. These finding comprehensively characterized DYRK1A as a potential new therapeutic approach in CRC, especially in late tumor stages.

Abstract

Colorectal cancer (CRC) is the third most common cancer worldwide and has an increasing incidence in younger populations. The dual-specificity tyrosine-regulated kinase (DYRK) family has been implicated in various diseases, including cancer. However, the role and contribution of the distinct family members in regulating CRC tumorigenesis has not been addressed yet. Herein, we used publicly available CRC patient datasets (TCGA RNA sequence) and several bioinformatics webtools to perform in silico analysis (GTEx, GENT2, GEPIA2, cBioPortal, GSCALite, TIMER2, and UALCAN). We aimed to investigate the DYRK family member expression pattern, prognostic value, and oncological roles in CRC. This study shed light on the role of distinct DYRK family members in CRC and their potential outcome predictive value. Based on mRNA level, DYRK1A is upregulated in late tumor stages, with lymph node and distant metastasis. All DYRKs were found to be implicated in cancer-associated pathways, indicating their key role in CRC pathogenesis. No significant DYRK mutations were identified, suggesting that DYRK expression variation in normal vs. tumor samples is likely linked to epigenetic regulation. The expression of DYRK1A and DYRK3 expression correlated with immune-infiltrating cells in the tumor microenvironment and was upregulated in MSI subtypes, pointing to their potential role as biomarkers for immunotherapy. This comprehensive bioinformatics analysis will set directions for future biological studies to further exploit the molecular basis of these findings and explore the potential of DYRK1A modulation as a novel targeted therapy for CRC.

Differential maturation and chaperone dependence of the paralogous protein kinases DYRK1A and DYRK1B

The HSP90/CDC37 chaperone system not only assists the maturation of many protein kinases but also maintains their structural integrity after folding. The interaction of mature kinases with the HSP90/CDC37 complex is governed by the conformational stability of the catalytic domain, while the initial folding of the protein kinase domain is mechanistically less well characterized. DYRK1A (Dual-specificity tyrosine (Y)-phosphorylation Regulated protein Kinase 1A) and DYRK1B are closely related protein kinases with discordant HSP90 client status. DYRK kinases stoichiometrically autophosphorylate on a tyrosine residue immediately after folding, which served us as a traceable marker of successful maturation. In the present study, we used bacterial expression systems to compare the capacity of autonomous maturation of DYRK1A and DYRK1B in the absence of eukaryotic cofactors or chaperones. Under these conditions, autophosphorylation of human DYRK1B was severely compromised when compared with DYRK1A or DYRK1B orthologs from zebrafish and Xenopus. Maturation of human DYRK1B could be restored by bacterial expression at lower temperatures, suggesting that folding was not absolutely dependent on eukaryotic chaperones. The differential folding properties of DYRK1A and DYRK1B were largely due to divergent sequences of the C-terminal lobes of the catalytic domain. Furthermore, the mature kinase domain of DYRK1B featured lower thermal stability than that of DYRK1A when exposed to heat challenge in vitro or in living cells. In summary, our study enhances the mechanistic understanding of the differential thermodynamic properties of two closely related protein kinases during initial folding and as mature kinases.

Protein quality control of DYRK family protein kinases by the Hsp90-Cdc37 molecular chaperone

The DYRK (Dual-specificity tYrosine-phosphorylation Regulated protein Kinase) family consists of five related protein kinases (DYRK1A, DYRK1B, DYRK2, DYRK3, DYRK4). DYRKs show homology to Drosophila Minibrain, and DYRK1A in human chromosome 21 is responsible for various neuronal disorders including human Down syndrome. Here we report identification of cellular proteins that associate with specific members of DYRKs. Cellular proteins with molecular masses of 90, 70, and 50-kDa associated with DYRK1B and DYRK4. These proteins were identified as molecular chaperones Hsp90, Hsp70, and Cdc37, respectively. Microscopic analysis of GFP-DYRKs showed that DYRK1A and DYRK1B were nuclear, while DYRK2, DYRK3, and DYRK4 were mostly cytoplasmic in COS7 cells. Overexpression of DYRK1B induced nuclear re-localization of these chaperones with DYRK1B. Treatment of cells with specific Hsp90 inhibitors, geldanamycin and 17-AAG, abolished the association of Hsp90 and Cdc37 with DYRK1B and DYRK4, but not of Hsp70. Inhibition of Hsp90 chaperone activity affected intracellular dynamics of DYRK1B and DYRK4. DYRK1B and DYRK4 underwent rapid formation of cytoplasmic punctate dots after the geldanamycin treatment, suggesting that the chaperone function of Hsp90 is required for prevention of protein aggregation of the target kinases. Prolonged inhibition of Hsp90 by geldanamycin, 17-AAG, or ganetespib, decreased cellular levels of DYRK1B and DYRK4. Finally, DYRK1B and DYRK4 were ubiquitinated in cells, and ubiquitinated DYRK1B and DYRK4 further increased by Hsp90 inhibition with geldanamycin. Taken together, these results indicate that Hsp90 and Cdc37 discriminate specific members of the DYRK kinase family and play an important role in quality control of these client kinases in cells.

Two novel variants in DYRK1B causative of AOMS3: expanding the clinical spectrum

Background

We investigated pathogenic DYRK1B variants causative of abdominal obesity-metabolic syndrome 3 (AOMS3) in a group of patients originally diagnosed with type 2 diabetes. All DYRK1B exons were analyzed in a sample of 509 unrelated adults with type 2 diabetes and 459 controls, all belonging to the DMS1 SIGMA-cohort (ExAC). We performed in silico analysis on missense variants using Variant Effect Predictor software. To evaluate co-segregation, predicted pathogenic variants were genotyped in other family members. We performed molecular dynamics analysis for the co-segregating variants.

Results

After filtering, Mendelian genotypes were confirmed in two probands bearing two novel variants, p.Arg252His and p.Lys68Gln. Both variants co-segregated with the AOMS3 phenotype in classic dominant autosomal inheritance with full penetrance. In silico analysis revealed impairment of the DYRK1B protein function by both variants. For the first time, we describe age-dependent variable expressivity of this entity, with central obesity and insulin resistance apparent in childhood; morbid obesity, severe hypertriglyceridemia, and labile type 2 diabetes appearing before 40 years of age; and hypertension emerging in the fifth decade of life. We also report the two youngest individuals suffering from AOMS3.

Conclusions

Monogenic forms of metabolic diseases could be misdiagnosed and should be suspected in families with several affected members and early-onset metabolic phenotypes that are difficult to control. Early diagnostic strategies and medical interventions, even before symptoms or complications appear, could be useful.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01924-z.

Druggable Transient Pockets in Protein Kinases

Drug discovery using small molecule inhibitors is reaching a stalemate due to low selectivity, adverse off-target effects and inevitable failures in clinical trials. Conventional chemical screening methods may miss potent small molecules because of their use of simple but outdated kits composed of recombinant enzyme proteins. Non-canonical inhibitors targeting a hidden pocket in a protein have received considerable research attention. Kii and colleagues identified an inhibitor targeting a transient pocket in the kinase DYRK1A during its folding process and termed it FINDY. FINDY exhibits a unique inhibitory profile; that is, FINDY does not inhibit the fully folded form of DYRK1A, indicating that the FINDY-binding pocket is hidden in the folded form. This intriguing pocket opens during the folding process and then closes upon completion of folding. In this review, we discuss previously established kinase inhibitors and their inhibitory mechanisms in comparison with FINDY. We also compare the inhibitory mechanisms with the growing concept of “cryptic inhibitor-binding sites.” These sites are buried on the inhibitor-unbound surface but become apparent when the inhibitor is bound. In addition, an alternative method based on cell-free protein synthesis of protein kinases may allow the discovery of small molecules that occupy these mysterious binding sites. Transitional folding intermediates would become alternative targets in drug discovery, enabling the efficient development of potent kinase inhibitors.

DYRK1A: a down syndrome-related dual protein kinase with a versatile role in tumorigenesis

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a dual kinase that can phosphorylate its own activation loop on tyrosine residue and phosphorylate its substrates on threonine and serine residues. It is the most studied member of DYRK kinases, because its gene maps to human chromosome 21 within the Down syndrome critical region (DSCR). DYRK1A overexpression was found to be responsible for the phenotypic features observed in Down syndrome such as mental retardation, early onset neurodegenerative, and developmental heart defects. Besides its dual activity in phosphorylation, DYRK1A carries the characteristic of duality in tumorigenesis. Many studies indicate its possible role as a tumor suppressor gene; however, others prove its pro-oncogenic activity. In this review, we will focus on its multifaceted role in tumorigenesis by explaining its participation in some cancer hallmarks pathways such as proliferative signaling, transcription, stress, DNA damage repair, apoptosis, and angiogenesis, and finally, we will discuss targeting DYRK1A as a potential strategy for management of cancer and neurodegenerative disorders.

Minibrain-related kinase/dual-specificity tyrosine-regulated kinase 1B implication in stem/cancer stem cells biology

Dual-specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B), also known as minibrain-related kinase (MIRK) is one of the best functionally studied members of the DYRK kinase family. DYRKs comprise a family of protein kinases that are emerging modulators of signal transduction pathways, cell proliferation and differentiation, survival, and cell motility. DYRKs were found to participate in several signaling pathways critical for development and cell homeostasis. In this review, we focus on the DYRK1B protein kinase from a functional point of view concerning the signaling pathways through which DYRK1B exerts its cell type-dependent function in a positive or negative manner, in development and human diseases. In particular, we focus on the physiological role of DYRK1B in behavior of stem cells in myogenesis, adipogenesis, spermatogenesis and neurogenesis, as well as in its pathological implication in cancer and metabolic syndrome. Thus, understanding of the molecular mechanisms that regulate signaling pathways is of high importance. Recent studies have identified a close regulatory connection between DYRK1B and the hedgehog (HH) signaling pathway. Here, we aim to bring together what is known about the functional integration and cross-talk between DYRK1B and several signaling pathways, such as HH, RAS and PI3K/mTOR/AKT, as well as how this might affect cellular and molecular processes in development, physiology, and pathology. Thus, this review summarizes the major known functions of DYRK1B kinase, as well as the mechanisms by which DYRK1B exerts its functions in development and human diseases focusing on the homeostasis of stem and cancer stem cells.

Acquired and modifiable cardiovascular risk factors in patients treated for cancer

Cardiac mortality is the leading cause of death secondary to malignancy in survivors of cancer. The field of cardio-oncology is dedicated to identifying and, if possible, modifying risk factors that contribute to significant cardiac morbidity and mortality. Many risk factors for the development of cancer-related cardiotoxicity overlap with risk factors in cardiovascular disease such as hypertension, obesity, dyslipidemia, and diabetes among others. These risk factors are usually modifiable while others such as genetics, type of malignancy, and need for chemotherapy are less modifiable. This article summarizes acquired and modifiable risk factors in both pediatric and adult patients treated for cancer.

Proline Hydroxylation Primes Protein Kinases for Autophosphorylation and Activation

Activation of dual-specificity tyrosine-phosphorylation-regulated kinases 1A and 1B (DYRK1A and DYRK1B) requires prolyl hydroxylation by PHD1 prolyl hydroxylase. Prolyl hydroxylation of DYRK1 initiates a cascade of events leading to the release of molecular constraints on von Hippel-Lindau (VHL) ubiquitin ligase tumor suppressor function. However, the proline residue of DYRK1 targeted by hydroxylation and the role of prolyl hydroxylation in tyrosine autophosphorylation of DYRK1 are unknown. We found that a highly conserved proline in the CMGC insert of the DYRK1 kinase domain is hydroxylated by PHD1, and this event precedes tyrosine autophosphorylation. Mutation of the hydroxylation acceptor proline precludes tyrosine autophosphorylation and folding of DYRK1, resulting in a kinase unable to preserve VHL function and lacking glioma suppression activity. The consensus proline sequence is shared by most CMGC kinases, and prolyl hydroxylation is essential for catalytic activation. Thus, formation of prolyl-hydroxylated intermediates is a novel mechanism of kinase maturation and likely a general mechanism of regulation of CMGC kinases in eukaryotes.

DCAF7/WDR68 is required for normal levels of DYRK1A and DYRK1B

Overexpression of the Dual-specificity Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A) gene contributes to the retardation, craniofacial anomalies, cognitive impairment, and learning and memory deficits associated with Down Syndrome (DS). DCAF7/HAN11/WDR68 (hereafter WDR68) binds DYRK1A and is required for craniofacial development. Accumulating evidence suggests DYRK1A-WDR68 complexes enable proper growth and patterning of multiple organ systems and suppress inappropriate cell growth/transformation by regulating the balance between proliferation and differentiation in multiple cellular contexts. Here we report, using engineered mouse C2C12 and human HeLa cell lines, that WDR68 is required for normal levels of DYRK1A. However, Wdr68 does not significantly regulate Dyrk1a mRNA expression levels and proteasome inhibition did not restore DYRK1A in cells lacking Wdr68 (Δwdr68 cells). Overexpression of WDR68 increased DYRK1A levels while overexpression of DYRK1A had no effect on WDR68 levels. We further report that WDR68 is similarly required for normal levels of the closely related DYRK1B kinase and that both DYRK1A and DYRK1B are essential for the transition from proliferation to differentiation in C2C12 cells. These findings reveal an additional role of WDR68 in DYRK1A-WDR68 and DYRK1B-WDR68 complexes.

Development of novel amide-derivatized 2,4-bispyridyl thiophenes as highly potent and selective Dyrk1A inhibitors. Part II: Identification of the cyclopropylamide moiety as a key modification

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1A) is a potential target in Alzheimer's disease (AD) because of the established correlation between its over-expression and generation of neurofibrillary tangles (NFT) as well as the accumulation of amyloid plaques. However, the use of Dyrk1A inhibitors requires a high degree of selectivity over closely related kinases. In addition, the physicochemical properties of the Dyrk1A inhibitors need to be controlled to enable CNS permeability. In the present study, we optimized our previously published 2,4-bispyridyl thiophene class of Dyrk1A inhibitors by the synthesis of a small library of amide derivatives, carrying alkyl, cycloalkyl, as well as acidic and basic residues. Among this library, the cyclopropylamido modification (compound 4b) was identified as being highly beneficial for several crucial properties. 4b displayed high potency and selectivity against Dyrk1A over closely related kinases in cell-free assays (IC50: Dyrk1A = 3.2 nM; Dyrk1B = 72.9 nM and Clk1 = 270 nM) and inhibited the Dyrk1A activity in HeLa cells with high efficacy (IC50: 43 nM), while no significant cytotoxicity was observed. In addition, the cyclopropylamido group conferred high metabolic stability and maintained the calculated physicochemical properties in a range compatible with a potential CNS activity. Thus, based on its favourable properties, 4b can be considered as a candidate for further in vivo testing in animal models of AD.

Mutational analysis of two residues in the DYRK homology box of the protein kinase DYRK1A

OBJECTIVE

Dual specificity tyrosine phosphorylation-regulated kinases (DYRK) contain a characteristic sequence motif (DYRK homology box, DH box) that is located N-terminal of the catalytic domain and supports the autophosphorylation of a conserved tyrosine during maturation of the catalytic domain. Two missense mutations in the DH box of human DYRK1B were recently identified as causative of a rare familiar form of metabolic syndrome. We have recently shown that these amino acid exchanges impair maturation of the kinase domain. Here we report the characterization of DYRK1A point mutants (D138P, K150C) that correspond to the pathogenic DYRK1B variants (H90P, R102C).

RESULTS

When expressed in HeLa cells, DYRK1A-D138P and K150C showed no significant difference from wild type DYRK1A regarding the activating tyrosine autophosphorylation or catalytic activity towards exogenous substrates. However, both DYRK1A variants were underphosphorylated on tyrosine when expressed in a bacterial cell free in vitro translation system. These results suggest that D138 and K150 participate in the maturation of the catalytic domain of DYRK1A albeit the mutation of these residues is compensated under physiological conditions.

Functional characterization of DYRK1A missense variants associated with a syndromic form of intellectual deficiency and autism

Haploinsufficiency of DYRK1A is a cause of a neurodevelopmental syndrome termed mental retardation autosomal dominant 7 (MRD7). Several truncation mutations, microdeletions and missense variants have been identified and result in a recognizable phenotypic profile, including microcephaly, intellectual disability, epileptic seizures, autism spectrum disorder and language delay. DYRK1A is an evolutionary conserved protein kinase which achieves full catalytic activity through tyrosine autophosphorylation. We used a heterologous mammalian expression system to explore the functional characteristics of pathogenic missense variants that affect the catalytic domain of DYRK1A. Four of the substitutions eliminated tyrosine autophosphorylation (L245R, F308V, S311F, S346P), indicating that these variants lacked kinase activity. Tyrosine phosphorylation of DYRK1A-L295F in mammalian cells was comparable to wild type, although the mutant showed lower catalytic activity and reduced thermodynamic stability in cellular thermal shift assays. In addition, we observed that one variant (DYRK1A-T588N) with a mutation outside the catalytic domain did not differ from wild-type DYRK1A in tyrosine autophosphorylation, catalytic activity or subcellular localization. These results suggest that the pathogenic missense variants in the catalytic domain of DYRK1A impair enzymatic function by affecting catalytic residues or by compromising the structural integrity of the kinase domain.

This article has an associated First Person interview with the first author of the paper.

Summary: We have analyzed the functional consequences of amino acid substitutions in the protein kinase DYRK1A that have been identified as pathogenic in patients with microcephaly, intellectual disability and autism.

A wake-up call to quiescent cancer cells - potential use of DYRK1B inhibitors in cancer therapy

Nondividing cancer cells are relatively resistant to chemotherapeutic drugs and environmental stress factors. Promoting cell cycle re-entry of quiescent cancer cells is a potential strategy to enhance the cytotoxicity of agents that target cycling cells. It is therefore important to elucidate the mechanisms by which these cells are maintained in the quiescent state. The protein kinase dual specificity tyrosine phosphorylation-regulated kinase 1B (DYRK1B) is overexpressed in a subset of cancers and maintains cellular quiescence by counteracting G0 /G1 -S phase transition. Specifically, DYRK1B controls the S phase checkpoint by stabilizing the cyclin-dependent kinase (CDK) inhibitor p27Kip1 and inducing the degradation of cyclin D. DYRK1B also stabilizes the DREAM complex that represses cell cycle gene expression in G0 arrested cells. In addition, DYRK1B enhances cell survival by upregulating antioxidant gene expression and reducing intracellular levels of reactive oxygen species (ROS). Substantial evidence indicates that depletion or inhibition of DYRK1B drives cell cycle re-entry and enhances apoptosis of those quiescent cancer cells with high expression of DYRK1B. Furthermore, small molecule DYRK1B inhibitors sensitize cells to the cytotoxic effects of anticancer drugs that target proliferating cells. These encouraging findings justify continued efforts to investigate the use of DYRK1B inhibitors to disrupt the quiescent state and overturn chemoresistance of noncycling cancer cells.

Emerging Roles of DYRK Kinases in Embryogenesis and Hedgehog Pathway Control

Hedgehog (Hh)/GLI signaling is an important instructive cue in various processes during embryonic development, such as tissue patterning, stem cell maintenance, and cell differentiation. It also plays crucial roles in the development of many pediatric and adult malignancies. Understanding the molecular mechanisms of pathway regulation is therefore of high interest. Dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs) comprise a group of protein kinases which are emerging modulators of signal transduction, cell proliferation, survival, and cell differentiation. Work from the last years has identified a close regulatory connection between DYRKs and the Hh signaling system. In this manuscript, we outline the mechanistic influence of DYRK kinases on Hh signaling with a focus on the mammalian situation. We furthermore aim to bring together what is known about the functional consequences of a DYRK-Hh cross-talk and how this might affect cellular processes in development, physiology, and pathology.