PSK, a novel STE20-like kinase derived from prostatic carcinoma that activates the c-Jun N-terminal kinase mitogen-activated protein kinase pathway and regulates actin cytoskeletal organization

A global phosphosite-correlated network map of Thousand And One Kinase 1 (TAOK1)

Thousand and one amino acid kinase 1 (TAOK1) is a sterile 20 family Serine/Threonine kinase linked to microtubule dynamics, checkpoint signaling, DNA damage response, and neurological functions. Molecular-level alterations of TAOK1 have been associated with neurodevelopment disorders and cancers. Despite their known involvement in physiological and pathophysiological processes, and as a core member of the hippo signaling pathway, the phosphoregulatory network of TAOK1 has not been visualized. Aimed to explore this network, we first analyzed the predominantly detected and differentially regulated TAOK1 phosphosites in global phosphoproteome datasets across diverse experimental conditions. Based on 709 qualitative and 210 quantitative differential cellular phosphoproteome datasets that were systematically assembled, we identified that phosphorylation at Ser421, Ser9, Ser965, and Ser445 predominantly represented TAOK1 in almost 75% of these datasets. Surprisingly, the functional role of all these phosphosites in TAOK1 remains unexplored. Hence, we employed a robust strategy to extract the phosphosites in proteins that significantly correlated in expression with predominant TAOK1 phosphosites. This led to the first categorization of the phosphosites including those in the currently known and predicted interactors, kinases, and substrates, that positively/negatively correlated with the expression status of each predominant TAOK1 phosphosites. Subsequently, we also analyzed the phosphosites in core proteins of the hippo signaling pathway. Based on the TAOK1 phosphoregulatory network analysis, we inferred the potential role of the predominant TAOK1 phosphosites. Especially, we propose pSer9 as an autophosphorylation and TAOK1 kinase activity-associated phosphosite and pS421, the most frequently detected phosphosite in TAOK1, as a significant regulatory phosphosite involved in the maintenance of genome integrity. Considering that the impact of all phosphosites that predominantly represent each kinase is essential for the efficient interpretation of global phosphoproteome datasets, we believe that the approach undertaken in this study is suitable to be extended to other kinases for accelerated research.

Pleiotropic functions of TAO kinases and their dysregulation in neurological disorders

Thousand and one amino acid kinases (TAOKs) are relatively understudied and functionally pleiotropic protein kinases that have emerged as important regulators of neurodevelopment. Through their conserved amino-terminal catalytic domain, TAOKs mediate phosphorylation at serine/threonine residues in their substrates, but it is their divergent regulatory carboxyl-terminal domains that confer both exquisite functional specification and cellular localization. In this Review, we discuss the physiological roles of TAOKs and the intricate signaling pathways, molecular interactions, and cellular behaviors they modulate-from cell stress responses, division, and motility to tissue homeostasis, immunity, and neurodevelopment. These insights are then integrated into an analysis of the known and potential impacts of disease-associated variants of TAOKs, with a focus on neurodevelopmental disorders, pain and addiction, and neurodegenerative diseases. Translating this foundation into clinical benefits for patients will require greater structural and functional differentiation of the TAOKs afforded by their individually specialized domains.

Spinal TAOK2 contributes to neuropathic pain via cGAS-STING activation in rats

Thousand and one amino acid kinase 2 (TAOK2) is a member of the mammalian sterile 20 kinase family and is implicated in neurodevelopmental disorders; however, its role in neuropathic pain remains unknown. Here, we found that TAOK2 was enriched and activated after chronic constriction injury (CCI) in the rat spinal dorsal horn. Meanwhile, cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling was also activated with hyperalgesia. Silencing TAOK2 reversed hyperalgesia and suppressed the activation of cGAS-STING signaling induced by CCI, while pharmacological activation of TAOK2 induced pain hypersensitivity and upregulation of cGAS-STING signaling in naive rats. Furthermore, pharmacological inhibition or gene silencing of cGAS-STING signaling attenuated CCI-induced hyperalgesia. Taken together, these data demonstrate that the activation of spinal TAOK2 contributes to CCI-induced hyperalgesia via cGAS-STING signaling activation, providing new molecular targets for the treatment of neuropathic pain.

TAOK3 Facilitates Esophageal Squamous Cell Carcinoma Progression and Cisplatin Resistance Through Augmenting Autophagy Mediated by IRGM

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers because of its robust aggressive phenotype and chemoresistance. TAO kinase belongs to mitogen-activated protein kinases, which mediate drug resistance in multiple cancers. However, the role of TAO kinase in ESCC progression and chemoresistance has never been explored. Here, it is reported that TAOK3 augments cell autophagy and further promotes ESCC progression and chemoresistance. Mechanistically, TAOK3 phosphorylates KMT2C at S4588 and strengthens the interaction between KMT2C and ETV5. Consequently, the nuclear translocation of KMT2C is increased, and the transcription of autophagy-relevant gene IRGM is further upregulated. Additionally, the inhibitor SBI-581 can significantly suppress cell autophagy mediated by TAOK3 and synergizes with cisplatin to treat ESCC in vitro and in vivo.

WNK1 is required during male pachynema to sustain fertility

WNK1 is an important regulator in many physiological functions, yet its role in male reproduction is unexplored. In the male germline, WNK1 is upregulated in preleptotene spermatocytes indicating possible function(s) in spermatogenic meiosis. Indeed, deletion of Wnk1 in mid-pachytene spermatocytes using the Wnt7a-Cre mouse led to male sterility which resembled non-obstructive azoospermia in humans, where germ cells failed to complete spermatogenesis and produced no sperm. Mechanistically, we found elevated MTOR expression and signaling in the Wnk1-depleted spermatocytes. As MTOR is a central mediator of translation, we speculated that translation may be accelerated in these spermatocytes. Supporting this, we found the acrosome protein, ACRBP to be prematurely expressed in the spermatocytes with Wnk1 deletion. Our study uncovered an MTOR-regulating factor in the male germline with potential implications in translation, and future studies will aim to understand how WNK1 regulates MTOR activity and impact translation on a broader spectrum.

Gene expression analysis of the Tao kinase family of Ste20p-like map kinase kinase kinases during early embryonic development in Xenopus laevis

Development of the vertebrate embryo requires strict coordination of a highly complex series of signaling cascades, that drive cell proliferation, differentiation, migration, and the general morphogenetic program. Members of the Map kinase signaling pathway are repeatedly required throughout development to activate the downstream effectors, ERK, p38, and JNK. Regulation of these pathways occurs at many levels in the signaling cascade, with the Map3Ks playing an essential role in target selection. The thousand and one amino acid kinases (Taoks) are Map3Ks that have been shown to activate both p38 and JNK and are linked to neurodevelopment in both invertebrate and vertebrate organisms. In vertebrates, there are three Taok paralogs (Taok1, Taok2, and Taok3) which have not yet been ascribed a role in early development. Here we describe the spatiotemporal expression of Taok1, Taok2, and Taok3 in the model organism Xenopus laevis. The X. laevis Tao kinases share roughly 80% identity to each other, with the bulk of the conservation in the kinase domain. Taok1 and Taok3 are highly expressed in pre-gastrula and gastrula stage embryos, with initial expression localized to the animal pole and later expression in the ectoderm and mesoderm. All three Taoks are expressed in the neural and tailbud stages, with overlapping expression in the neural tube, notochord, and many anterior structures (including branchial arches, brain, otic vesicles, and eye). The expression patterns described here provide evidence that the Tao kinases may play a central role in early development, in addition to their function during neural development, and establish a framework to better understand the developmental roles of Tao kinase signaling.

Neurodevelopmental disorder-associated mutations in TAOK1 reveal its function as a plasma membrane remodeling kinase

Mutations in TAOK1, which encodes a serine-threonine kinase, are associated with both autism spectrum disorder (ASD) and neurodevelopmental delay (NDD). Here, we investigated the molecular function of this evolutionarily conserved kinase and the mechanisms through which TAOK1 mutations may lead to neuropathology. We found that TAOK1 was abundant in neurons in the mammalian brain and remodeled the neuronal plasma membrane through direct association with phosphoinositides. Our characterization of four NDD-associated TAOK1 mutations revealed that these mutants were catalytically inactive and were aberrantly trapped in a membrane-bound state, which induced abnormal membrane protrusions. Expression of these TAOK1 mutants in cultured mouse hippocampal neurons led to abnormal growth of the dendritic arbor. The coiled-coil region carboxyl-terminal to the kinase domain was predicted to fold into a triple helix, and this region directly bound phospholipids and was required for both membrane association and induction of aberrant protrusions. Autophosphorylation of threonine-440 and threonine-443 in the triple-helical region by the kinase domain blocked the plasma membrane association of TAOK1. These findings define TAOK1 as a plasma membrane remodeling kinase and reveal the underlying mechanisms through which TAOK1 dysfunction may lead to neurodevelopmental disorders.

TAOK2 is an ER-localized kinase that catalyzes the dynamic tethering of ER to microtubules

The endoplasmic reticulum (ER) depends on extensive association with the microtubule (MT) cytoskeleton for its structure and mitotic inheritance. However, mechanisms that underlie coupling of ER membranes to MTs are poorly understood. We have identified thousand and one amino acid kinase 2 (TAOK2) as a pleiotropic protein kinase that mediates tethering of ER to MTs. In human cells, TAOK2 localizes in distinct ER subdomains via transmembrane helices and an adjacent amphipathic region. Through its C-terminal tail, TAOK2 directly binds MTs, coupling ER membranes to the MT cytoskeleton. In TAOK2 knockout cells, although ER-membrane dynamics are increased, movement of ER along growing MT plus ends is disrupted. ER-MT tethering is tightly regulated by catalytic activity of TAOK2, perturbation of which leads to defects in ER morphology, association with MTs, and cell division. Our study identifies TAOK2 as an ER-MT tether and reveals a kinase-regulated mechanism for control of ER dynamics.

Clinical and Neurobiological Aspects of TAO Kinase Family in Neurodevelopmental Disorders

Despite the complexity of neurodevelopmental disorders (NDDs), from their genotype to phenotype, in the last few decades substantial progress has been made in understanding their pathophysiology. Recent accumulating evidence shows the relevance of genetic variants in thousand and one (TAO) kinases as major contributors to several NDDs. Although it is well-known that TAO kinases are a highly conserved family of STE20 kinase and play important roles in multiple biological processes, the emerging roles of TAO kinases in neurodevelopment and NDDs have yet to be intensively discussed. In this review article, we summarize the potential roles of the TAO kinases based on structural and biochemical analyses, present the genetic data from clinical investigations, and assess the mechanistic link between the mutations of TAO kinases, neuropathology, and behavioral impairment in NDDs. We then offer potential perspectives from basic research to clinical therapies, which may contribute to fully understanding how TAO kinases are involved in NDDs.

Kinase Signaling in Dendritic Development and Disease

Dendrites undergo extensive growth and remodeling during their lifetime. Specification of neurites into dendrites is followed by their arborization, maturation, and functional integration into synaptic networks. Each of these distinct developmental processes is spatially and temporally controlled in an exquisite fashion. Protein kinases through their highly specific substrate phosphorylation regulate dendritic growth and plasticity. Perturbation of kinase function results in aberrant dendritic growth and synaptic function. Not surprisingly, kinase dysfunction is strongly associated with neurodevelopmental and psychiatric disorders. Herein, we review, (a) key kinase pathways that regulate dendrite structure, function and plasticity, (b) how aberrant kinase signaling contributes to dendritic dysfunction in neurological disorders and (c) emergent technologies that can be applied to dissect the role of protein kinases in dendritic structure and function.

Research Advances in the Molecular Functions and Relevant Diseases of TAOKs, Novel STE20 Kinase Family Members

As serine/threonine-protein kinases, Thousand and One Kinases(TAOKs) are members of the GCKlike superfamily, one of two well-known branches of the Ste20 kinase family. Within the last two decades, three functionally similar kinases, namely TAOK1-3, were identified. TAOKs are involved in many molecular and cellular events. Scholars widely believe that TAOKs act as kinases upstream of the MAPK cascade and as factors that interact with MST family kinases, the cytoskeleton, and apoptosis-associated proteins. Therefore, TAOKs are thought to function in tumorigenesis. Additionally, TAOKs participate in signal transduction induced by Notch, TCR, and IL-17. Recent studies found that TAOKs play roles in a series of diseases and conditions, such as the central nervous system dysfunction, herpes viral infection, immune system imbalance, urogenital system malformation during development, cardiovascular events, and childhood obesity. Therefore, inhibitory chemicals targeting TAOKs may be of great significance as potential drugs for these diseases.

WNK1 regulates uterine homeostasis and its ability to support pregnancy

WNK1 (with no lysine [K] kinase 1) is an atypical kinase protein ubiquitously expressed in humans and mice. A mutation in its encoding gene causes hypertension in humans, which is associated with abnormal ion homeostasis. WNK1 is critical for in vitro decidualization in human endometrial stromal cells, thereby demonstrating its importance in female reproduction. Using a mouse model, WNK1 was ablated in the female reproductive tract to define its in vivo role in uterine biology. Loss of WNK1 altered uterine morphology, causing endometrial epithelial hyperplasia, adenomyotic features, and a delay in embryo implantation, ultimately resulting in compromised fertility. Combining transcriptomic, proteomic, and interactomic analyses revealed a potentially novel regulatory pathway whereby WNK1 represses AKT phosphorylation through protein phosphatase 2A (PP2A) in endometrial cells from both humans and mice. We show that WNK1 interacted with PPP2R1A, the alpha isoform of the PP2A scaffold subunit. This maintained the levels of PP2A subunits and stabilized its activity, which then dephosphorylated AKT. Therefore, loss of WNK1 reduced PP2A activity, causing AKT hypersignaling. Using FOXO1 as a readout of AKT activity, we demonstrate that there was escalated FOXO1 phosphorylation and nuclear exclusion, leading to a disruption in the expression of genes that are crucial for embryo implantation.

The Diverse Roles of TAO Kinases in Health and Diseases

Thousand and one kinases (TAOKs) are members of the MAP kinase kinase kinase (MAP3K) family. Three members of this subfamily, TAOK1, 2, and 3, have been identified in mammals. It has been shown that TAOK1, 2 and 3 regulate the p38 MAPK and Hippo signaling pathways, while TAOK 1 and 2 modulate the SAPK/JNK cascade. Furthermore, TAOKs are involved in additional interactions with other cellular proteins and all of these pathways modulate vital physiological and pathophysiological responses in cells and tissues. Dysregulation of TAOK-related pathways is implicated in the development of diseases including inflammatory and immune disorders, cancer and drug resistance, and autism and Alzheimer’s diseases. This review collates current knowledge concerning the roles of TAOKs in protein–protein interaction, signal transduction, physiological regulation, and pathogenesis and summarizes the recent development of TAOK-specific inhibitors that have the potential to ameliorate TAOKs’ effects in pathological situations.

Thousand and one kinase 1 protects MCAO-induced cerebral ischemic stroke in rats by decreasing apoptosis and pro-inflammatory factors

Background: Birth hypoxia causes neonatal mortality and morbidity. Hypoxia/ischemia can facilitate brain damage, causing various kinds of diseases, such as ischemic stroke. It is necessary to understand the potential underlying mechanisms of ischemic stroke. Previous studies revealed the involvement of thousand and one kinase 1 (TAOK1) in many cellular processes. Methods: Herein, middle cerebral artery (MCA) occlusion (MCAO) was performed in rats to establish ischemic stroke in the animal model, and cortical neural stem cells from rats were treated with oxygen-glucose deprivation (OGD) to induce ischemic stroke cell model. The animal model of ischemic stroke was validated by Bederson and Zea-Longa neurological deficit scores and rotarod test. TAOK1 expression was examined by quantitative real-time PCR (qRT-PCR), Western blot, and immunofluorescent staining both in vivo and in vitro. Result: Compared with sham animals, the MCAO rats showed a significant increase in the neurological scores, and obvious motor behavioral deficits. Meanwhile, there was increased apoptosis and inflammatory response in the model group. TAOK1 overexpression reversed the OGD-induced cell injury, while TAOK1 knockdown exhibited the opposing effects. On the mechanism, the OGD-induced suppression of PI3K/AKT, and activation of mitogen-activated protein kinase (MAPK) signaling pathways were abolished by TAOK1 overexpression, and aggravated by TAOK1 knockdown in vitro. Moreover, we proved that the inhibitory effect of TAOK1 on OGD-induced apoptosis was dependent on the intracellular kinase activity. Conclusion: TAOK1 protected MCAO-induced cerebral ischemic stroke by decreasing the pro-inflammatory factors and apoptosis via PI3K/AKT and MAPK signaling pathways.

Neurodevelopmental trajectory and modifiers of 16p11.2 microdeletion: A follow-up study of four Chinese children carriers

Background

Neurodevelopmental disorders (NDDs) are a group of disorders with high genetic and phenotypic heterogeneities. The 16p11.2 microdeletion has been implicated as an important genetic risk factor for NDDs.

Methods

Multiple genetic tests were used to detect the 16p11.2 microdeletion from 918 Chinese children with NDDs. Targeted sequencing of genes in the 16p11.2 interval was performed in all carriers of the 16p11.2 microdeletion, and whole‐genome expression profiling analysis was performed for the patient carriers and normal carriers in their intra‐family.

Results

Three patients carrying the 16p11.2 microdeletion were screened out, indicating a frequency of 0.33% for the 16p11.2 microdeletion in this cohort. We reviewed the neurodevelopmental trajectories of the 16p11.2 microdeletion carriers from childhood to puberty and confirmed that this microdeletion was associated with abnormal neurodevelopment, with varied neurodevelopmental phenotypes. A differential PRRT2 genotype (rs10204, T>C) was identified between patients and normal carriers of the 16p11.2 microdeletion. Moreover, the determination of differential whole‐genome expression profiling demonstrated the destruction of the top‐ranked network in neurogenesis and accounted for observation of abnormal neurodevelopmental phenotypes in the 16p11.2 microdeletion carriers.

Conclusions

We have provided the frequency of the 16p11.2 microdeletion in a Chinese pediatric NDD cohort with a variable NDD phenotype from childhood to puberty, which is useful for Chinese geneticists/pediatricians to conduct the 16p11.2 microdeletion testing in children with NDDs.

A role for Taok2 in Listeria monocytogenes vacuolar escape

The bacterial pathogen Listeria monocytogenes invades host cells, ruptures the internalization vacuole, and reaches the cytosol for replication. A high-content small interfering RNA (siRNA) microscopy screen allowed us to identify epithelial cell factors involved in L. monocytogenes vacuolar rupture, including the serine/threonine kinase Taok2. Kinase activity inhibition using a specific drug validated a role for Taok2 in favoring L. monocytogenes cytoplasmic access. Furthermore, we showed that Taok2 recruitment to L. monocytogenes vacuoles requires the presence of pore-forming toxin listeriolysin O. Overall, our study identified the first set of host factors modulating L. monocytogenes vacuolar rupture and cytoplasmic access in epithelial cells.

Rnd3 interacts with TAO kinases and contributes to mitotic cell rounding and spindle positioning

Rnd3 is an atypical Rho family protein that is constitutively GTP bound, and acts on membranes to induce loss of actin stress fibers and cell rounding. Phosphorylation of Rnd3 promotes 14-3-3 binding and its relocation to the cytosol. Here, we show that Rnd3 binds to the thousand-and-one amino acid kinases TAOK1 and TAOK2 in vitro and in cells. TAOK1 and TAOK2 can phosphorylate serine residues 210, 218 and 240 near the C-terminus of Rnd3, and induce Rnd3 translocation from the plasma membrane to the cytosol. TAOKs are activated catalytically during mitosis and Rnd3 phosphorylation on serine 210 increases in dividing cells. Rnd3 depletion by RNAi inhibits mitotic cell rounding and spindle centralization, and delays breakdown of the intercellular bridge between two daughter cells. Our results show that TAOKs bind, phosphorylate and relocate Rnd3 to the cytosol and that Rnd3 contributes to mitotic cell rounding, spindle positioning and cytokinesis. Rnd3 can therefore participate in the regulation of early and late mitosis and may also act downstream of TAOKs to affect the cytoskeleton.

Conserved Tao Kinase Activity Regulates Dendritic Arborization, Cytoskeletal Dynamics, and Sensory Function in Drosophila

Dendritic arborization is highly regulated and requires tight control of dendritic growth, branching, cytoskeletal dynamics, and ion channel expression to ensure proper function. Abnormal dendritic development can result in altered network connectivity, which has been linked to neurodevelopmental disorders, including autism spectrum disorders (ASDs). How neuronal growth control programs tune dendritic arborization to ensure function is still not fully understood. Using Drosophila dendritic arborization (da) neurons as a model, we identified the conserved Ste20-like kinase Tao as a negative regulator of dendritic arborization. We show that Tao kinase activity regulates cytoskeletal dynamics and sensory channel localization required for proper sensory function in both male and female flies. We further provide evidence for functional conservation of Tao kinase, showing that its ASD-linked human ortholog, Tao kinase 2 (Taok2), could replace Drosophila Tao and rescue dendritic branching, dynamic microtubule alterations, and behavioral defects. However, several ASD-linked Taok2 variants displayed impaired rescue activity, suggesting that Tao/Taok2 mutations can disrupt sensory neuron development and function. Consistently, we show that Tao kinase activity is required in developing and as well as adult stages for maintaining normal dendritic arborization and sensory function to regulate escape and social behavior. Our data suggest an important role for Tao kinase signaling in cytoskeletal organization to maintain proper dendritic arborization and sensory function, providing a strong link between developmental sensory aberrations and behavioral abnormalities relevant for Taok2-dependent ASDs.SIGNIFICANCE STATEMENT Autism spectrum disorders (ASDs) are linked to abnormal dendritic arbors. However, the mechanisms of how dendritic arbors develop to promote functional and proper behavior are unclear. We identified Drosophila Tao kinase, the ortholog of the ASD risk gene Taok2, as a regulator of dendritic arborization in sensory neurons. We show that Tao kinase regulates cytoskeletal dynamics, controls sensory ion channel localization, and is required to maintain somatosensory function in vivo Interestingly, ASD-linked human Taok2 mutations rendered it nonfunctional, whereas its WT form could restore neuronal morphology and function in Drosophila lacking endogenous Tao. Our findings provide evidence for a conserved role of Tao kinase in dendritic development and function of sensory neurons, suggesting that aberrant sensory function might be a common feature of ASDs.

RYK, a receptor of noncanonical Wnt ligand Wnt5a, is positively correlated with gastric cancer tumorigenesis and potential of liver metastasis

Gastric cancer (GC) is the most prevalent human cancer around the globe. In GC, Wnt signaling is deregulated, and receptor-like tyrosine kinase (RYK) coreceptors have been identified to interact with noncanonical Wnt ligand Wnt5a. We, therefore, aimed to evaluate the role of RYK in GC development and metastasis. GC tumor samples were collected from 250 GC patients. Expressions of RYK, as well as markers for the epithelial-mesenchymal transition (EMT), such as N-cadherin and E-cadherin, were subjected to correlation analysis with clinicopathological features. Endogenous RYK expression levels were compared in GC cell lines with ascending metastatic potentials followed by stable RYK knockdown. Effect of RYK knockdown on GC cell migration, invasion, and EMT phenotype were assessed in vitro, and on GC tumor growth in vivo in a xenograft rodent model. Particularly, liver metastasis potential of tail vein-injected GC cells was also analyzed following RYK knockdown. RYK was highly correlated with liver metastasis of GC tumors and the expression profiles of EMT markers toward the mesenchymal tendency. RYK expression was also positively correlated with the metastasis potential of GC cells. RYK knockdown not only inhibited migration, invasion, and EMT of GC cells in vitro, but also suppressed tumorigenesis and liver metastasis of GC cells in vivo using the mouse xenograft model. RYK is highly correlated with GC tumorigenesis and potential of liver metastasis, suggesting it may be a novel oncogenic factor of the noncanonical Wnt signaling pathway contributing to GC.NEW & NOTEWORTHY RYK is highly correlated with gastric cancer tumorigenesis and the potential of liver metastasis, suggesting it may be a novel oncogenic factor of the noncanonical Wnt signaling pathway contributing to gastric cancer.

Altered TAOK2 activity causes autism-related neurodevelopmental and cognitive abnormalities through RhoA signaling

Atypical brain connectivity is a major contributor to the pathophysiology of neurodevelopmental disorders (NDDs) including autism spectrum disorders (ASDs). TAOK2 is one of several genes in the 16p11.2 microdeletion region, but whether it contributes to NDDs is unknown. We performed behavioral analysis on Taok2 heterozygous (Het) and knockout (KO) mice and found gene dosage-dependent impairments in cognition, anxiety, and social interaction. Taok2 Het and KO mice also have dosage-dependent abnormalities in brain size and neural connectivity in multiple regions, deficits in cortical layering, dendrite and synapse formation, and reduced excitatory neurotransmission. Whole-genome and -exome sequencing of ASD families identified three de novo mutations in TAOK2 and functional analysis in mice and human cells revealed that all the mutations impair protein stability, but they differentially impact kinase activity, dendrite growth, and spine/synapse development. Mechanistically, loss of Taok2 activity causes a reduction in RhoA activation, and pharmacological enhancement of RhoA activity rescues synaptic phenotypes. Together, these data provide evidence that TAOK2 is a neurodevelopmental disorder risk gene and identify RhoA signaling as a mediator of TAOK2-dependent synaptic development.

Kinases in synaptic development and neurological diseases

Neuronal morphogenesis and synapse development is essential for building a functioning nervous system, and defects in these processes are associated with neurological disorders. Our understanding of molecular components and signalling events that contribute to neuronal development and pathogenesis is limited. Genes associated with neurodevelopmental and neurodegenerative diseases provide entry points for elucidating molecular events that contribute to these conditions. Several protein kinases, enzymes that regulate protein function by phosphorylating their substrates, are genetically linked to neurological disorders. Identifying substrates of these kinases is key to discovering their function and providing insight for possible therapies. In this review, we describe how various methods for kinase-substrate identification helped elucidate kinase signalling pathways important for neuronal development and function. We describe recent advances on roles of kinases TAOK2, TNIK and CDKL5 in neuronal development and the converging pathways of LRRK2, PINK1 and GAK in Parkinson's Disease.

Role of WNT5A receptors FZD5 and RYK in prostate cancer cells

Prostate cancer is the most common malignancy in men and has a high propensity to metastasize to bone. WNT5A has recently been implicated in the progression of prostate cancer, however, the receptors that mediate its effects remain unknown. Here, we identified Wnt receptors that are highly expressed in prostate cancer and investigated which of these receptors mediate the anti-tumor effects of WNT5A in prostate cancer in vitro.

Extensive in vitro analyses revealed that the WNT5A receptors FZD5 and RYK mediate the anti-tumor effects of WNT5A on prostate cancer cells. Knock-down of FZD5 completely abrogated the anti-proliferative effect of WNT5A in PC3 cells. In contrast, knock-down of RYK and FZD8 did not rescue the inhibition of proliferation after WNT5A overexpression. In contrast, RYK knock-down inhibited the pro-apoptotic effect of WNT5A in PC3 cells by 60%, whereas the knock-down of either FZD5 or FZD8 further stimulated apoptosis after WNT5A overexpression (by 33% and 234%, respectively). Surface plasmon resonance analysis indicated that WNT5A has a 30% stronger binding response to FZD5 than to RYK. Further investigations using a tissue microarray revealed that expression of RYK is increased in advanced prostate cancer tumor stages, but is not associated with survival of prostate cancer patients. In contrast, patients with low local FZD5 expression, in particular in combination with low WNT5A expression, showed a longer disease-specific survival.

In conclusion, WNT5A/FZD5 and WNT5A/RYK signaling are both involved in mediating the pro-apoptotic and anti-proliferative effects of WNT5A in prostate cancer.

A new TAO kinase inhibitor reduces tau phosphorylation at sites associated with neurodegeneration in human tauopathies

In Alzheimer’s disease (AD) and related tauopathies, the microtubule-associated protein tau is highly phosphorylated and aggregates to form neurofibrillary tangles that are characteristic of these neurodegenerative diseases. Our previous work has demonstrated that the thousand-and-one amino acid kinases (TAOKs) 1 and 2 phosphorylate tau on more than 40 residues in vitro. Here we show that TAOKs are phosphorylated and active in AD brain sections displaying mild (Braak stage II), intermediate (Braak stage IV) and advanced (Braak stage VI) tau pathology and that active TAOKs co-localise with both pre-tangle and tangle structures. TAOK activity is also enriched in pathological tau containing sarkosyl-insoluble extracts prepared from AD brain. Two new phosphorylated tau residues (T123 and T427) were identified in AD brain, which appear to be targeted specifically by TAOKs. A new small molecule TAOK inhibitor (Compound 43) reduced tau phosphorylation on T123 and T427 and also on additional pathological sites (S262/S356 and S202/T205/S208) in vitro and in cell models. The TAOK inhibitor also decreased tau phosphorylation in differentiated primary cortical neurons without affecting markers of synapse and neuron health. Notably, TAOK activity also co-localised with tangles in post-mortem frontotemporal lobar degeneration (FTLD) brain tissue. Furthermore, the TAOK inhibitor decreased tau phosphorylation in induced pluripotent stem cell derived neurons from FTLD patients, as well as cortical neurons from a transgenic mouse model of tauopathy (Tau35 mice). Our results demonstrate that abnormal TAOK activity is present at pre-tangles and tangles in tauopathies and that TAOK inhibition effectively decreases tau phosphorylation on pathological sites. Thus, TAOKs may represent a novel target to reduce or prevent tau-associated neurodegeneration in tauopathies.

Targeting TAO Kinases Using a New Inhibitor Compound Delays Mitosis and Induces Mitotic Cell Death in Centrosome Amplified Breast Cancer Cells

Thousand-and-one amino acid kinases (TAOK) 1 and 2 are activated catalytically during mitosis and can contribute to mitotic cell rounding and spindle positioning. Here, we characterize a compound that inhibits TAOK1 and TAOK2 activity with IC50 values of 11 to 15 nmol/L, is ATP-competitive, and targets these kinases selectively. TAOK inhibition or depletion in centrosome-amplified SKBR3 or BT549 breast cancer cell models increases the mitotic population, the percentages of mitotic cells displaying amplified centrosomes and multipolar spindles, induces cell death, and inhibits cell growth. In contrast, nontumorigenic and dividing bipolar MCF-10A breast cells appear less dependent on TAOK activity and can complete mitosis and proliferate in the presence of the TAOK inhibitor. We demonstrate that TAOK1 and TAOK2 localize to the cytoplasm and centrosomes respectively during mitosis. Live cell imaging shows that the TAOK inhibitor prolongs the duration of mitosis in SKBR3 cells, increases mitotic cell death, and reduces the percentages of cells exiting mitosis, whereas MCF-10A cells continue to divide and proliferate. Over 80% of breast cancer tissues display supernumerary centrosomes, and tumor cells frequently cluster extra centrosomes to avoid multipolar mitoses and associated cell death. Consequently, drugs that stimulate centrosome declustering and induce multipolarity are likely to target dividing centrosome-amplified cancer cells preferentially, while sparing normal bipolar cells. Our results demonstrate that TAOK inhibition can enhance centrosome declustering and mitotic catastrophe in cancer cells, and these proteins may therefore offer novel therapeutic targets suitable for drug inhibition and the potential treatment of breast cancers, where supernumerary centrosomes occur. Mol Cancer Ther; 16(11); 2410-21. ©2017 AACR.

TAOK2 Kinase Mediates PSD95 Stability and Dendritic Spine Maturation through Septin7 Phosphorylation

Abnormalities in dendritic spines are manifestations of several neurodevelopmental and psychiatric diseases. TAOK2 is one of the genes in the 16p11.2 locus, copy number variations of which are associated with autism and schizophrenia. Here, we show that the kinase activity of the serine/threonine kinase encoded by TAOK2 is required for spine maturation. TAOK2 depletion results in unstable dendritic protrusions, mislocalized shaft-synapses, and loss of compartmentalization of NMDA receptor-mediated calcium influx. Using chemical-genetics and mass spectrometry, we identified several TAOK2 phosphorylation targets. We show that TAOK2 directly phosphorylates the cytoskeletal GTPase Septin7, at an evolutionary conserved residue. This phosphorylation induces translocation of Septin7 to the spine, where it associates with and stabilizes the scaffolding protein PSD95, promoting dendritic spine maturation. This study provides a mechanistic basis for postsynaptic stability and compartmentalization via TAOK2-Sept7 signaling, with implications toward understanding the potential role of TAOK2 in neurological deficits associated with the 16p11.2 region.

Activity-Based Protein Profiling Shows Heterogeneous Signaling Adaptations to BRAF Inhibition

Patients with BRAF V600E mutant melanoma are typically treated with targeted BRAF kinase inhibitors, such as vemurafenib and dabrafenib. Although these drugs are initially effective, they are not curative. Most of the focus to date has been upon genetic mechanisms of acquired resistance; therefore, we must better understand the global signaling adaptations that mediate escape from BRAF inhibition. In the current study, we have used activity-based protein profiling (ABPP) with ATP-analogue probes to enrich kinases and other enzyme classes that contribute to BRAF inhibitor (BRAFi) resistance in four paired isogenic BRAFi-naïve/resistant cell line models. Our analysis showed these cell line models, which also differ in their PTEN status, have considerable heterogeneity in their kinase ATP probe uptake in comparing both naïve cells and adaptations to chronic drug exposure. A number of kinases including FAK1, SLK, and TAOK2 had increased ATP probe uptake in BRAFi resistant cells, while KHS1 (M4K5) and BRAF had decreased ATP probe uptake in the BRAFi-resistant cells. Gene ontology (GO) enrichment analysis revealed BRAFi resistance is associated with a significant enhancement in ATP probe uptake in proteins implicated in cytoskeletal organization and adhesion, and decreases in ATP probe uptake in proteins associated with cell metabolic processes. The ABPP approach was able to identify key phenotypic mediators critical for each BRAFi resistant cell line. Together, these data show that common phenotypic adaptations to BRAF inhibition can be mediated through very different signaling networks, suggesting considerable redundancy within the signaling of BRAF mutant melanoma cells.

Discovery of novel TAOK2 inhibitor scaffolds from high-throughput screening

The MAP3K (Mitogen Activated Protein Kinase Kinase Kinase) TAOK2 (Thousand-And-One Kinase 2) is an activator of p38 MAP kinase cascade that is up-regulated in response to environmental stresses. A synthetic lethal screen performed using a NSCLC (non-small cell lung cancer) cell line, and a second screen identifying potential modulators of autophagy have implicated TAOK2 as a potential cancer therapeutic target. Using a 200,000 compound high throughput screen, we identified three specific small molecule compounds that inhibit the kinase activity of TAOK2. These compounds also showed inhibition of autophagy. Based on SAR (structure-activity relationship) studies, we have predicted the modifications on the reactive groups for the three compounds.

Coordination of Recombination with Meiotic Progression in the Caenorhabditis elegans Germline by KIN-18, a TAO Kinase That Regulates the Timing of MPK-1 Signaling

Meiosis is a tightly regulated process requiring coordination of diverse events. A conserved ERK/MAPK-signaling cascade plays an essential role in the regulation of meiotic progression. The Thousand And One kinase (TAO) kinase is a MAPK kinase kinase, the meiotic role of which is unknown. We have analyzed the meiotic functions of KIN-18, the homolog of mammalian TAO kinases, in Caenorhabditis elegans. We found that KIN-18 is essential for normal meiotic progression; mutants exhibit accelerated meiotic recombination as detected both by analysis of recombination intermediates and by crossover outcome. In addition, ectopic germ-cell differentiation and enhanced levels of apoptosis were observed in kin-18 mutants. These defects correlate with ectopic activation of MPK-1 that includes premature, missing, and reoccurring MPK-1 activation. Late progression defects in kin-18 mutants are suppressed by inhibiting an upstream activator of MPK-1 signaling, KSR-2. However, the acceleration of recombination events observed in kin-18 mutants is largely MPK-1-independent. Our data suggest that KIN-18 coordinates meiotic progression by modulating the timing of MPK-1 activation and the progression of recombination events. The regulation of the timing of MPK-1 activation ensures the proper timing of apoptosis and is required for the formation of functional oocytes. Meiosis is a conserved process; thus, revealing that KIN-18 is a novel regulator of meiotic progression in C. elegans would help to elucidate TAO kinase's role in germline development in higher eukaryotes.

Brain MRI abnormalities and spectrum of neurological and clinical findings in three patients with proximal 16p11.2 microduplication

The phenotype of recurrent ∼600 kb microdeletion and microduplication on proximal 16p11.2 is characterized by a spectrum of neurodevelopmental impairments including developmental delay and intellectual disability, epilepsy, autism and psychiatric disorders which are all subject to incomplete penetrance and variable expressivity. A variety of brain MRI abnormalities were reported in patients with 16p11.2 rearrangements, but no systematic correlation has been studied among patients with similar brain anomalies, their neurodevelopmental and clinical phenotypes. We present three patients with the proximal 16p11.2 microduplication exhibiting significant developmental delay, anxiety disorder and other variable clinical features. Our patients have abnormal brain MRI findings of cerebral T2 hyperintense foci (3/3) and ventriculomegaly (2/3). The neuroradiological or neurological findings in two cases prompted an extensive diagnostic work-up. One patient has exhibited neurological regression and progressive vision impairment and was diagnosed with juvenile neuronal ceroid-lipofuscinosis. We compare the clinical course and phenotype of these patients in regard to the clinical significance of the cerebral lesions and the need for MRI surveillance. We conclude that in all three patients the lesions were not progressive, did not show any sign of malignant transformation and could not be correlated to specific clinical features. We discuss potential etiologic mechanisms that may include overexpression of genes within the duplicated region involved in control of cell proliferation and complex molecular mechanisms such as the MAPK/ERK pathway. Systematic studies in larger cohorts are needed to confirm our observation and to establish the prevalence and clinical significance of these neuroanatomical abnormalities in patients with 16p11.2 duplications.

Deleted copy number variation of Hanwoo and Holstein using next generation sequencing at the population level

BACKGROUND

Copy number variation (CNV), a source of genetic diversity in mammals, has been shown to underlie biological functions related to production traits. Notwithstanding, there have been few studies conducted on CNVs using next generation sequencing at the population level.

RESULTS

Illumina NGS data was obtained for ten Holsteins, a dairy cattle, and 22 Hanwoo, a beef cattle. The sequence data for each of the 32 animals varied from 13.58-fold to almost 20-fold coverage. We detected a total of 6,811 deleted CNVs across the analyzed individuals (average length = 2732.2 bp) corresponding to 0.74% of the cattle genome (18.6 Mbp of variable sequence). By examining the overlap between CNV deletion regions and genes, we selected 30 genes with the highest deletion scores. These genes were found to be related to the nervous system, more specifically with nervous transmission, neuron motion, and neurogenesis. We regarded these genes as having been effected by the domestication process. Further analysis of the CNV genotyping information revealed 94 putative selected CNVs and 954 breed-specific CNVs.

CONCLUSIONS

This study provides useful information for assessing the impact of CNVs on cattle traits using NGS at the population level.

Sorafenib suppresses JNK-dependent apoptosis through inhibition of ZAK

Sorafenib is U.S. Food and Drug Adminstration-approved for the treatment of renal cell carcinoma and hepatocellular carcinoma and has been combined with numerous other targeted therapies and chemotherapies in the treatment of many cancers. Unfortunately, as with other RAF inhibitors, patients treated with sorafenib have a 5% to 10% rate of developing cutaneous squamous cell carcinoma (cSCC)/keratoacanthomas. Paradoxical activation of extracellular signal-regulated kinase (ERK) in BRAF wild-type cells has been implicated in RAF inhibitor-induced cSCC. Here, we report that sorafenib suppresses UV-induced apoptosis specifically by inhibiting c-jun-NH(2)-kinase (JNK) activation through the off-target inhibition of leucine zipper and sterile alpha motif-containing kinase (ZAK). Our results implicate suppression of JNK signaling, independent of the ERK pathway, as an additional mechanism of adverse effects of sorafenib. This has broad implications for combination therapies using sorafenib with other modalities that induce apoptosis.

Prostate-derived sterile 20-like kinases (PSKs/TAOKs) phosphorylate tau protein and are activated in tangle-bearing neurons in Alzheimer disease

In Alzheimer disease (AD), the microtubule-associated protein tau is highly phosphorylated and aggregates into characteristic neurofibrillary tangles. Prostate-derived sterile 20-like kinases (PSKs/TAOKs) 1 and 2, members of the sterile 20 family of kinases, have been shown to regulate microtubule stability and organization. Here we show that tau is a good substrate for PSK1 and PSK2 phosphorylation with mass spectrometric analysis of phosphorylated tau revealing more than 40 tau residues as targets of these kinases. Notably, phosphorylated residues include motifs located within the microtubule-binding repeat domain on tau (Ser-262, Ser-324, and Ser-356), sites that are known to regulate tau-microtubule interactions. PSK catalytic activity is enhanced in the entorhinal cortex and hippocampus, areas of the brain that are most susceptible to Alzheimer pathology, in comparison with the cerebellum, which is relatively spared. Activated PSK is associated with neurofibrillary tangles, dystrophic neurites surrounding neuritic plaques, neuropil threads, and granulovacuolar degeneration bodies in AD brain. By contrast, activated PSKs and phosphorylated tau are rarely detectible in immunostained control human brain. Our results demonstrate that tau is a substrate for PSK and suggest that this family of kinases could contribute to the development of AD pathology and dementia.

JNK pathway activation is controlled by Tao/TAOK3 to modulate ethanol sensitivity

Neuronal signal transduction by the JNK MAP kinase pathway is altered by a broad array of stimuli including exposure to the widely abused drug ethanol, but the behavioral relevance and the regulation of JNK signaling is unclear. Here we demonstrate that JNK signaling functions downstream of the Sterile20 kinase family gene tao/Taok3 to regulate the behavioral effects of acute ethanol exposure in both the fruit fly Drosophila and mice. In flies tao is required in neurons to promote sensitivity to the locomotor stimulant effects of acute ethanol exposure and to establish specific brain structures. Reduced expression of key JNK pathway genes substantially rescued the structural and behavioral phenotypes of tao mutants. Decreasing and increasing JNK pathway activity resulted in increased and decreased sensitivity to the locomotor stimulant properties of acute ethanol exposure, respectively. Further, JNK expression in a limited pattern of neurons that included brain regions implicated in ethanol responses was sufficient to restore normal behavior. Mice heterozygous for a disrupted allele of the homologous Taok3 gene (Taok3Gt) were resistant to the acute sedative effects of ethanol. JNK activity was constitutively increased in brains of Taok3Gt/+ mice, and acute induction of phospho-JNK in brain tissue by ethanol was occluded in Taok3Gt/+ mice. Finally, acute administration of a JNK inhibitor conferred resistance to the sedative effects of ethanol in wild-type but not Taok3Gt/+ mice. Taken together, these data support a role of a TAO/TAOK3-JNK neuronal signaling pathway in regulating sensitivity to acute ethanol exposure in flies and in mice.

Taok2 controls behavioral response to ethanol in mice

Despite recent advances in the understanding of ethanol's biological action, many of the molecular targets of ethanol and mechanisms behind ethanol's effect on behavior remain poorly understood. In an effort to identify novel genes, the products of which regulate behavioral responses to ethanol, we recently identified a mutation in the dtao gene that confers resistance to the locomotor stimulating effect of ethanol in Drosophila. dtao encodes a member of the Ste20 family of serine/threonine kinases implicated in MAP kinase signaling pathways. In this study, we report that conditional ablation of the mouse dtao homolog, Taok2, constitutively and specifically in the nervous system, results in strain-specific and overlapping alterations in ethanol-dependent behaviors. These data suggest a functional conservation of dtao and Taok2 in mediating ethanol's biological action and identify Taok2 as a putative candidate gene for ethanol use disorders in humans.

Protein kinases of the Hippo pathway: regulation and substrates

The "Hippo" signaling pathway has emerged as a major regulator of cell proliferation and survival in metazoans. The pathway, as delineated by genetic and biochemical studies in Drosophila, consists of a kinase cascade regulated by cell-cell contact and cell polarity that inhibits the transcriptional coactivator Yorkie and its proliferative, anti-differentiation, antiapoptotic transcriptional program. The core pathway components are the GC kinase Hippo, which phosphorylates the noncatalytic polypeptide Mats/Mob1 and, with the assistance of the scaffold protein Salvador, phosphorylates the ndr-family kinase Lats. In turn phospho-Lats, after binding to phospho-Mats, autoactivates and phosphorylates Yorkie, resulting in its nuclear exit. Hippo also uses the scaffold protein Furry and a different Mob protein to control another ndr-like kinase, the morphogenetic regulator Tricornered. Architecturally homologous kinase cascades consisting of a GC kinase, a Mob protein, a scaffolding polypeptide and an ndr-like kinase are well described in yeast; in Saccharomyces cerevisiae, e.g., the MEN pathway promotes mitotic exit whereas the RAM network, using a different GC kinase, Mob protein, scaffold and ndr-like kinase, regulates cell polarity and morphogenesis. In mammals, the Hippo orthologs Mst1 and Mst2 utilize the Salvador ortholog WW45/Sav1 and other scaffolds to regulate the kinases Lats1/Lats2 and ndr1/ndr2. As in Drosophila, murine Mst1/Mst2, in a redundant manner, negatively regulate the Yorkie ortholog YAP in the epithelial cells of the liver and gut; loss of both Mst1 and Mst2 results in hyperproliferation and tumorigenesis that can be largely negated by reduction or elimination of YAP. Despite this conservation, considerable diversification in pathway composition and regulation is already evident; in skin, e.g., YAP phosphorylation is independent of Mst1Mst2 and Lats1Lats2. Moreover, in lymphoid cells, Mst1/Mst2, under the control of the Rap1 GTPase and independent of YAP, promotes integrin clustering, actin remodeling and motility while restraining the proliferation of naïve T cells. This review will summarize current knowledge of the structure and regulation of the kinases Hippo/Mst1&2, their noncatalytic binding partners, Salvador and the Rassf polypeptides, and their major substrates Warts/Lats1&2, Trc/ndr1&2, Mats/Mob1 and FOXO.

Genome-wide transcriptome profiling reveals the functional impact of rare de novo and recurrent CNVs in autism spectrum disorders

Copy-number variants (CNVs) are a major contributor to the pathophysiology of autism spectrum disorders (ASDs), but the functional impact of CNVs remains largely unexplored. Because brain tissue is not available from most samples, we interrogated gene expression in lymphoblasts from 244 families with discordant siblings in the Simons Simplex Collection in order to identify potentially pathogenic variation. Our results reveal that the overall frequency of significantly misexpressed genes (which we refer to here as outliers) identified in probands and unaffected siblings does not differ. However, in probands, but not their unaffected siblings, the group of outlier genes is significantly enriched in neural-related pathways, including neuropeptide signaling, synaptogenesis, and cell adhesion. We demonstrate that outlier genes cluster within the most pathogenic CNVs (rare de novo CNVs) and can be used for the prioritization of rare CNVs of potentially unknown significance. Several nonrecurrent CNVs with significant gene-expression alterations are identified (these include deletions in chromosomal regions 3q27, 3p13, and 3p26 and duplications at 2p15), suggesting that these are potential candidate ASD loci. In addition, we identify distinct expression changes in 16p11.2 microdeletions, 16p11.2 microduplications, and 7q11.23 duplications, and we show that specific genes within the 16p CNV interval correlate with differences in head circumference, an ASD-relevant phenotype. This study provides evidence that pathogenic structural variants have a functional impact via transcriptome alterations in ASDs at a genome-wide level and demonstrates the utility of integrating gene expression with mutation data for the prioritization of genes disrupted by potentially pathogenic mutations.

Mammalian MAPK signal transduction pathways activated by stress and inflammation: a 10-year update

The mammalian stress-activated families of mitogen-activated protein kinases (MAPKs) were first elucidated in 1994, and by 2001, substantial progress had been made in identifying the architecture of the pathways upstream of these kinases as well as in cataloguing candidate substrates. This information remains largely sound. Nevertheless, an informed understanding of the physiological and pathophysiological roles of these kinases remained to be accomplished. In the past decade, there has been an explosion of new work using RNAi in cells, as well as transgenic, knockout and conditional knockout technology in mice that has provided valuable insight into the functions of stress-activated MAPK pathways. These findings have important implications in our understanding of organ development, innate and acquired immunity, and diseases such as atherosclerosis, tumorigenesis, and type 2 diabetes. These new developments bring us within striking distance of the development and validation of novel treatment strategies. Herein we first summarize the molecular components of the mammalian stress-regulated MAPK pathways and their regulation as described thus far. We then review some of the in vivo functions of these pathways.

Autism spectrum disorder susceptibility gene TAOK2 affects basal dendrite formation in the neocortex

How neurons develop their morphology is an important question in neurobiology. Here we describe a new pathway that specifically affects the formation of basal dendrites and axonal projections in cortical pyramidal neurons. We report that thousand-and-one-amino acid 2 kinase (TAOK2), also known as TAO2, is essential for dendrite morphogenesis. TAOK2 downregulation impairs basal dendrite formation in vivo without affecting apical dendrites. Moreover, TAOK2 interacts with Neuropilin 1 (Nrp1), a receptor protein that binds the secreted guidance cue Semaphorin 3A (Sema3A). TAOK2 overexpression restores dendrite formation in cultured cortical neurons from Nrp1(Sema-) mice, which express Nrp1 receptors incapable of binding Sema3A. TAOK2 overexpression also ameliorates the basal dendrite impairment resulting from Nrp1 downregulation in vivo. Finally, Sema3A and TAOK2 modulate the formation of basal dendrites through the activation of the c-Jun N-terminal kinase (JNK). These results delineate a pathway whereby Sema3A and Nrp1 transduce signals through TAOK2 and JNK to regulate basal dendrite development in cortical neurons.

Prostate-derived sterile 20-like kinases (PSKs/TAOKs) are activated in mitosis and contribute to mitotic cell rounding and spindle positioning

Prostate-derived sterile 20-like kinases (PSKs) 1-α, 1-β, and 2 are members of the germinal-center kinase-like sterile 20 family of kinases. Previous work has shown that PSK 1-α binds and stabilizes microtubules whereas PSK2 destabilizes microtubules. Here, we have investigated the activation and autophosphorylation of endogenous PSKs and show that their catalytic activity increases as cells accumulate in G(2)/M and declines as cells exit mitosis. PSKs are stimulated in synchronous HeLa cells as they progress through mitosis, and these proteins are activated catalytically during each stage of mitosis. During prophase and metaphase activated PSKs are located in the cytoplasm and at the spindle poles, and during telophase and cytokinesis stimulated PSKs are present in trans-Golgi compartments. In addition, small interfering RNA (siRNA) knockdown of PSK1-α/β or PSK2 expression inhibits mitotic cell rounding as well as spindle positioning and centralization. These results show that PSK catalytic activity increases during mitosis and suggest that these proteins can contribute functionally to mitotic cell rounding and spindle centralization during cell division.

The WNKs: atypical protein kinases with pleiotropic actions

WNKs are serine/threonine kinases that comprise a unique branch of the kinome. They are so-named owing to the unusual placement of an essential catalytic lysine. WNKs have now been identified in diverse organisms. In humans and other mammals, four genes encode WNKs. WNKs are widely expressed at the message level, although data on protein expression is more limited. Soon after the WNKs were identified, mutations in genes encoding WNK1 and -4 were determined to cause the human disease familial hyperkalemic hypertension (also known as pseudohypoaldosteronism II, or Gordon's Syndrome). For this reason, a major focus of investigation has been to dissect the role of WNK kinases in renal regulation of ion transport. More recently, a different mutation in WNK1 was identified as the cause of hereditary sensory and autonomic neuropathy type II, an early-onset autosomal disease of peripheral sensory nerves. Thus the WNKs represent an important family of potential targets for the treatment of human disease, and further elucidation of their physiological actions outside of the kidney and brain is necessary. In this review, we describe the gene structure and mechanisms regulating expression and activity of the WNKs. Subsequently, we outline substrates and targets of WNKs as well as effects of WNKs on cellular physiology, both in the kidney and elsewhere. Next, consequences of these effects on integrated physiological function are outlined. Finally, we discuss the known and putative pathophysiological relevance of the WNKs.

Proteasome-mediated degradation and functions of hematopoietic progenitor kinase 1 in pancreatic cancer

Hematopoietic progenitor kinase 1 (HPK1) regulates stress responses, proliferation, and apoptosis in hematopoietic cells. In this study, we examined the expression, regulation, and functions of HPK1 in pancreatic ductal adenocarcinomas (PDA). We found that loss of HPK1 protein expression correlated significantly with the progression of pancreatic intraepithelial neoplasias (P = 0.001) and development of invasive PDA. Similarly, HPK1 protein was not expressed in any of eight PDA cell lines examined but was expressed in immortalized human pancreatic duct epithelial (HPDE) cells. There was no difference in HPK1 mRNA levels in PDA cell lines or primary PDA compared with those in HPDE cells or ductal epithelium in chronic pancreatitis and normal pancreas, respectively. Treatment of Panc-1 cells with a proteasome inhibitor, MG132, increased the HPK1 protein levels in a dose-dependent manner, suggesting that alteration in proteasome activity contributes to the loss of HPK1 protein expression in pancreatic cancer. Like the endogenous HPK1, both wild-type HPK1 and its kinase-dead mutant, HPK1-M46, overexpressed in Panc-1 cells, were also targeted by proteasome-mediated degradation. After MG132 withdrawal, wild-type HPK1 protein expression was markedly decreased within 24 hours, but kinase-dead HPK1 mutant protein expression was sustained for up to 96 hours. Therefore, HPK1 kinase activities were required for the loss of HPK1 protein in PDAs. Furthermore, restoring wild-type HPK1 protein in PDA cells led to the increase in p21 and p27 protein expression and cell cycle arrest. Thus, HPK1 may function as a novel tumor suppressor and its loss plays a critical role in pancreatic cancer.

Gene network and canonical pathway analysis in prostate cancer: a microarray study

The molecular mechanism playing a role in the development of prostate cancer (PCA) is not well defined. We decided to determine the changes in gene expression in PCA tissues and to compare them to those in non-cancerous samples. Prostate tissue samples were collected by needle biopsy from 21 PCA and 10 benign prostate hyperplasic (BPH) patients. Total RNA was isolated, cDNA was synthesized, and gene expression levels were determined by microarray method. In the progression to PCA, 738 up-regulated and 515 down-regulated genes were detected in samples. Analysis using Ingenuity Pathway Analysis (IPA) software revealed that 466 network and 423 functions-pathways eligible genes were up-regulated, and 363 network and 342 functions-pathways eligible genes were down-regulated. Up-regulated networks were identified around IL-1beta and insulin-like growth factor-1 (IGF-1) genes. The NFKB gene was centered around two up- and down-regulated networks. Up-regulated canonical pathways were assigned and four of them were evaluated in detail: acute phase response, hepatic fibrosis, actin cytoskeleton, and coagulation pathways. Axonal guidance signaling was the most significant down-regulated canonical pathway. Our data provide not only networks between the genes for understanding the biologic properties of PCA but also useful pathway maps for future understanding of disease and the construction of new therapeutic targets.

The detection of MAPK signaling

Mitogen-activated protein kinase (MAPK) cascades are central pathways that participate in the intracellular transmission of extracellular signals. Each of the MAPK signaling cascades seems to consist of three to five tiers of protein kinases that sequentially activate each other by phosphorylation. Since the majority of MAPK cascade components are kinases, the methods used to detect their activation involve determining phosphorylation state and protein kinase activities. The primary method describes the use of immunoblotting with specific anti-phospho antibody to detect activation of MAPK components. Alternative methods described are immunoprecipitation of desired protein kinases followed by phosphorylation of specific substrates and the use of an in-gel kinase assay. These methods have proven useful in the study of the MAPK signaling cascades.

Spred1 and TESK1--two new interaction partners of the kinase MARKK/TAO1 that link the microtubule and actin cytoskeleton

The signaling from MARKK/TAO1 to the MAP/microtubule affinity-regulating kinase MARK/Par1 to phosphorylated microtubule associated proteins (MAPs) renders microtubules dynamic and plays a role in neurite outgrowth or polarity development. Because hyperphosphorylation of Tau at MARK target sites is a hallmark of Alzheimer neurodegeneration, we searched for upstream regulators by the yeast two-hybrid approach and identified two new interaction partners of MARKK, the regulatory Sprouty-related protein with EVH-1 domain1 (Spred1) and the testis-specific protein kinase (TESK1). Spred1-MARKK binding has no effect on the activity of MARKK; therefore, it does not change microtubule (MT) stability. Spred1-TESK1 binding causes inhibition of TESK1. Because TESK1 can phosphorylate cofilin and thus stabilizes F-actin stress fibers, the inhibition of TESK1 by Spred1 makes F-actin fibers dynamic. A third element in this interaction triangle is that TESK1 binds to and inhibits MARKK. Thus, in Chinese hamster ovary (CHO) cells the elevation of MARKK results in MT disruption (via activation of MARK/Par1 and phosphorylation of MAPs), but this can be blocked by TESK1. Similarly, enhanced TESK1 activity results in increased stress fibers (via phospho-cofilin), but this can be blocked by elevating Spred1. Thus, the three-way interaction between Spred1, MARKK, and TESK1 represents a pathway that links regulation of both the microtubule- and F-actin cytoskeleton.

Ras-MEK-ERK signaling cascade regulates androgen receptor element-inducible gene transcription and DNA synthesis in prostate cancer cells

Treatment of prostate cancer (CaP) patients frequently involves androgen ablation, but resistance often develops and androgen-insensitive tumors emerge. The molecular basis for the development of refractory CaP that grows in an androgen-independent manner is poorly understood, but alterations in growth factor signaling pathways are likely to be involved. We examined the growth factor modulation of androgen-receptor element (ARE)-inducible luciferase reporter gene activity and consequent DNA synthesis as a measure of proliferative growth in androgen-dependent LNCaP or androgen-independent PC3 or DU145 CaP cells. The synthetic androgen R1881 stimulated ARE-inducible reporter gene activity and prostate-specific antigen expression in LNCaP cells and the MEK/ERK inhibitor U0126 or the anti-androgen bicalutamide (casodex) prevented both of these responses. Activated V12-Ha-Ras expression in LNCaP cells also stimulated ARE-inducible gene transcription, and U0126 or the farnesyltransferase inhibitor FTI-277 but not bicalutamide blocked this. ARE-inducible reporter gene activity was elevated already in PC3 cells, and ERK was constitutively activated in serum-starved LNCaP or DU145 cells. U0126 inhibited each of these responses and also inhibited DNA synthesis in all 3 CaP cell lines. These results demonstrate that chronic stimulation of the Ras-MEK-ERK signaling pathway can sustain ARE-inducible gene transcription and growth of CaP cells, and suggests that components of this pathway may offer targets for cancer therapy.

Biological Cross-talk between WNK1 and the Transforming Growth Factor β-Smad Signaling Pathway

WNKs (with no lysine (K)), unique serine/threonine protein kinases, have been best studied in the context of cell volume regulation and ion homeostasis. Here we describe a biological link between WNKs and transforming growth factor (TGF) beta-Smad signaling. Both WNK1 and WNK4 directly bind to and phosphorylate Smad2. Knockdown of WNK1 in HeLa cells using small interfering RNA reduces Smad2 protein expression; this decrease is at least partially due to down-regulation of Smad2 transcription. In contrast, phosphorylated Smad2 significantly accumulated in the nucleus as a consequence of depletion of WNK1, resulting in Smad-mediated transcriptional responses. In addition, TGFbeta-induced target gene transcripts were increased in WNK1 small interfering RNA cells. These findings suggest WNK1 as a dual modulator of TGFbeta-Smad signaling pathways.

Maternal Nanos represses hid/skl-dependent apoptosis to maintain the germ line in Drosophila embryos

Nanos (Nos) is an evolutionarily conserved protein essential for the survival of primordial germ cells. In Drosophila, maternal Nos partitions into pole cells and suppresses apoptosis to permit proper germ-line development. However, how this critical event is regulated by Nos has remained elusive. Here, we report that Nos represses apoptosis of pole cells by suppressing translation of head involution defective (hid), a member of the RHG gene family that is required for Caspase activation. In addition, we demonstrate that hid acts in concert with another RHG gene, sickle (skl), to induce apoptosis. Expression of skl is induced in pole cells by maternal tao-1, a ste20-like serine/threonine kinase. Tao-1-dependent skl expression is required to potentiate hid activity. However, skl expression is largely suppressed in normal pole cells. Once the pole cells lack maternal Nos, Tao-1-dependent skl expression is fully activated, suggesting that skl expression is also restricted by Nos. These findings provide the first evidence that the germ line is maintained through the regulated expression of RHG genes.

Nonreceptor tyrosine kinases in prostate cancer

BACKGROUND

Carcinoma of the prostate (CaP) is the most commonly diagnosed cancer in men in the United States. Signal transduction molecules such as tyrosine kinases play important roles in CaP. Src, a nonreceptor tyrosine kinase (NRTK) and the first proto-oncogene discovered is shown to participate in processes such as cell proliferation and migration in CaP. Underscoring NRTK's and, specifically, Src's importance in cancer is the recent approval by the US Food and Drug Administration of dasatinib, the first commercial Src inhibitor for clinical use in chronic myelogenous leukemia (CML). In this review we will focus on NRTKs and their roles in the biology of CaP.

MATERIALS AND METHODS

Publicly available literature from PubMed regarding the topic of members of NRTKs in CaP was searched and reviewed.

RESULTS

Src, FAK, JaK1/2, and ETK are involved in processes indispensable to the biology of CaP: cell growth, migration, invasion, angiogenesis, and apoptosis.

CONCLUSIONS

Src emerges as a common signaling and regulatory molecule in multiple biological processes in CaP. Src's relative importance in particular stages of CaP, however, required further definition. Continued investigation of NRTKs will increase our understanding of their biological function and potential role as new therapeutic targets.

Prostate-derived sterile 20-like kinase 1-alpha induces apoptosis. JNK- and caspase-dependent nuclear localization is a requirement for membrane blebbing

We have demonstrated previously that full-length prostate-derived sterile 20-like kinase 1-alpha (PSK1-alpha) binds to microtubules via its C terminus and regulates their organization and stability independently of its catalytic activity. Here we have shown that apoptotic and microtubule-disrupting agents promote catalytic activation, C-terminal cleavage, and nuclear translocation of endogenous phosphoserine 181 PSK1-alpha and activated N-terminal PSK1-alpha-induced apoptosis. PSK1-alpha, unlike its novel isoform PSK1-beta, stimulated the c-Jun N-terminal kinase (JNK) pathway, and the nuclear localization of PSK1-alpha and its induction of cell contraction, membrane blebbing, and apoptotic body formation were dependent on JNK activity. PSK1-alpha was also a caspase substrate, and the broad spectrum caspase inhibitor benzyloxycarbonyl-VAD-fluoromethyl ketone or mutation of a putative caspase recognition motif ((916)DPGD(919)) blocked nuclear localization of PSK1-alpha and its induction of membrane blebs. Additional inhibition of caspase 9 was needed to prevent cell contraction. PSK1-alpha is therefore a bifunctional kinase that associates with microtubules, and JNK- and caspase-mediated removal of its C-terminal microtubule-binding domain permits nuclear translocation of the N-terminal region of PSK1-alpha and its induction of apoptosis.