The kinesin I family member KIF5C is a novel substrate for protein kinase CK2

Identification of SNPs and Candidate Genes for Milk Production Ability in Yorkshire Pigs

Sow milk production ability is an important limiting factor impacting suboptimal growth and the survival of piglets. Through pig genetic improvement, litter sizes have been increased. Larger litters need more suckling mammary glands, which results in increased milk from the lactating sow. Hence, there is much significance to exploring sow lactation performance. For milk production ability, it is not practical to directly measure the milk yield, we used litter weight gain (LWG) throughout sow lactation as an indicator. In this study, we estimated the heritability of LWG, namely, 0.18 ± 0.07. We then performed a GWAS, and detected seven significant SNPs, namely, Sus scrofa Chromosome (SSC) 2: ASGA0010040 (p = 7.73E-11); SSC2:MARC0029355 (p = 1.30E-08), SSC6: WU_10.2_6_65751151 (p = 1.32E-10), SSC7: MARC0058875 (p = 4.99E-09), SSC10: WU_10.2_10_49571394 (p = 6.79E-08), SSC11: M1GA0014659 (p = 1.19E-07), and SSC15: MARC0042106 (p = 1.16E-07). We performed the distribution of phenotypes corresponding to the genotypes of seven significant SNPs and showed that ASGA0010040, MARC0029355, MARC0058875, WU_10.2_10_49571394, M1GA0014659, and MARC0042106 had extreme phenotypic values that corresponded to the homozygous genotypes, while the intermediate values corresponded to the heterozygous genotypes. We screened for flanking regions ± 200 kb nearby the seven significant SNPs, and identified 38 genes in total. Among them, 28 of the candidates were involved in lactose metabolism, colostrum immunity, milk protein, and milk fat by functional enrichment analysis. Through the combined analysis between 28 candidate genes and transcriptome data of the sow mammary gland, we found nine commons (ANO3, MUC15, DISP3, FBXO6, CLCN6, HLA-DRA, SLA-DRB1, SLA-DQB1, and SLA-DQA1). Furthermore, by comparing the chromosome positions of the candidate genes with the quantitative trait locus (QTLs) as previously reported, a total of 17 genes were found to be within 0.86–94.02 Mb of the reported QTLs for sow milk production ability, in which, NAV2 was found to be located with 0.86 Mb of the QTL region ssc2: 40936355. In conclusion, we identified seven significant SNPs located on SSC2, 6, 7, 10, 11, and 15, and propose 28 candidate genes for the ability to produce milk in Yorkshire pigs, 10 of which were key candidates.

Role of Protein Kinase CK2 in Aberrant Lipid Metabolism in Cancer

Uncontrolled proliferation is a feature defining cancer and it is linked to the ability of cancer cells to effectively adapt their metabolic needs in response to a harsh tumor environment. Metabolic reprogramming is considered a hallmark of cancer and includes increased glucose uptake and processing, and increased glutamine utilization, but also the deregulation of lipid and cholesterol-associated signal transduction, as highlighted in recent years. In the first part of the review, we will (i) provide an overview of the major types of lipids found in eukaryotic cells and their importance as mediators of intracellular signaling pathways (ii) analyze the main metabolic changes occurring in cancer development and the role of oncogenic signaling in supporting aberrant lipid metabolism and (iii) discuss combination strategies as powerful new approaches to cancer treatment. The second part of the review will address the emerging role of CK2, a conserved serine/threonine protein kinase, in lipid homeostasis with an emphasis regarding its function in lipogenesis and adipogenesis. Evidence will be provided that CK2 regulates these processes at multiple levels. This suggests that its pharmacological inhibition combined with dietary restrictions and/or inhibitors of metabolic targets could represent an effective way to undermine the dependency of cancer cells on lipids to interfere with tumor progression.

β-catenin stimulates Tcf7l1 degradation through recruitment of casein kinase 2 in mouse embryonic stem cells

Activation of the Wnt/β-catenin signaling pathway by the inhibition of glycogen synthase kinase-3 (GSK-3) will induce Tcf7l1 protein degradation to effectively promote embryonic stem cell (ESC) self-renewal. However, the exact mechanism remains unclear. Here, we found that inhibition of casein kinase 2 (Csnk2) by TBB or DMAT was sufficient to block the reduction of the Tcf7l1 protein induced by CHIR99021, a specific inhibitor of GSK-3. Similarly, downregulation of Csnk2 increased the Tcf7l1 level. In contrast, overexpression of Csnk2 significantly decreased Tcf7l1 protein stability in mouse ESCs. Notably, Csnk2α1 controls Tcf7l1 turnover to a greater degree than the other two isoforms of Csnk2, Csnk2α2 and Csnk2β, as Csnk2α1-overexpressing mouse ESCs exhibited the lowest level of Tcf7l1. Csnk2α1 interacted with and phosphorylated Tcf7l1. In addition, the association of Csnk2α1 and Tcf7l1 was enhanced by CHIR99021. Our study demonstrated, for the first time, that Csnk2 is involved in Tcf7l1 turnover mediated by the Wnt/β-catenin signaling pathway. These results expand our understanding of the function and circuit of Wnt/β-catenin signaling pathway in ESCs.

Protein Kinase CK2-A Putative Target for the Therapy of Diabetes Mellitus?

Since diabetes is a global epidemic, the development of novel therapeutic strategies for the treatment of this disease is of major clinical interest. Diabetes is differentiated in two types: type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). T1DM arises from an autoimmune destruction of insulin-producing β-cells whereas T2DM is characterized by an insulin resistance, an impaired insulin reaction of the target cells, and/or dysregulated insulin secretion. In the past, a growing number of studies have reported on the important role of the protein kinase CK2 in the regulation of the survival and endocrine function of pancreatic β-cells. In fact, inhibition of CK2 is capable of reducing cytokine-induced loss of β-cells and increases insulin expression as well as secretion by various pathways that are regulated by reversible phosphorylation of proteins. Moreover, CK2 inhibition modulates pathways that are involved in the development of diabetes and prevents signal transduction, leading to late complications such as diabetic retinopathy. Hence, targeting CK2 may represent a novel therapeutic strategy for the treatment of diabetes.

A Journey through the Cytoskeleton with Protein Kinase CK2

Substrate pleiotropicity, a very acidic phosphorylation consensus sequence, and an apparent uncontrolled activity, are the main features of CK2, a Ser/Thr protein kinase that is required for a plethora of cell functions. Not surprisingly, CK2 appears to affect cytoskeletal structures and correlated functions such as cell shape, mechanical integrity, cell movement and division. This review outlines our current knowledge of how CK2 regulates cytoskeletal structures, and discusses involved pathways and molecular mechanisms.

Prion protein inhibits fast axonal transport through a mechanism involving casein kinase 2

Prion diseases include a number of progressive neuropathies involving conformational changes in cellular prion protein (PrP^c) that may be fatal sporadic, familial or infectious. Pathological evidence indicated that neurons affected in prion diseases follow a dying-back pattern of degeneration. However, specific cellular processes affected by PrP^c that explain such a pattern have not yet been identified. Results from cell biological and pharmacological experiments in isolated squid axoplasm and primary cultured neurons reveal inhibition of fast axonal transport (FAT) as a novel toxic effect elicited by PrP^c. Pharmacological, biochemical and cell biological experiments further indicate this toxic effect involves casein kinase 2 (CK2) activation, providing a molecular basis for the toxic effect of PrP^c on FAT. CK2 was found to phosphorylate and inhibit light chain subunits of the major motor protein conventional kinesin. Collectively, these findings suggest CK2 as a novel therapeutic target to prevent the gradual loss of neuronal connectivity that characterizes prion diseases.

Mutant spastin proteins promote deficits in axonal transport through an isoform-specific mechanism involving casein kinase 2 activation

Mutations of various genes cause hereditary spastic paraplegia (HSP), a neurological disease involving dying-back degeneration of upper motor neurons. From these, mutations in the SPAST gene encoding the microtubule-severing protein spastin account for most HSP cases. Cumulative genetic and experimental evidence suggests that alterations in various intracellular trafficking events, including fast axonal transport (FAT), may contribute to HSP pathogenesis. However, the mechanisms linking SPAST mutations to such deficits remain largely unknown. Experiments presented here using isolated squid axoplasm reveal inhibition of FAT as a common toxic effect elicited by spastin proteins with different HSP mutations, independent of microtubule-binding or severing activity. Mutant spastin proteins produce this toxic effect only when presented as the tissue-specific M1 isoform, not when presented as the ubiquitously-expressed shorter M87 isoform. Biochemical and pharmacological experiments further indicate that the toxic effects of mutant M1 spastins on FAT involve casein kinase 2 (CK2) activation. In mammalian cells, expression of mutant M1 spastins, but not their mutant M87 counterparts, promotes abnormalities in the distribution of intracellular organelles that are correctable by pharmacological CK2 inhibition. Collectively, these results demonstrate isoform-specific toxic effects of mutant M1 spastin on FAT, and identify CK2 as a critical mediator of these effects.

Microtubule Dynamics in Neuronal Development, Plasticity, and Neurodegeneration

Neurons are the basic information-processing units of the nervous system. In fulfilling their task, they establish a structural polarity with an axon that can be over a meter long and dendrites with a complex arbor, which can harbor ten-thousands of spines. Microtubules and their associated proteins play important roles during the development of neuronal morphology, the plasticity of neurons, and neurodegenerative processes. They are dynamic structures, which can quickly adapt to changes in the environment and establish a structural scaffold with high local variations in composition and stability. This review presents a comprehensive overview about the role of microtubules and their dynamic behavior during the formation and maturation of processes and spines in the healthy brain, during aging and under neurodegenerative conditions. The review ends with a discussion of microtubule-targeted therapies as a perspective for the supportive treatment of neurodegenerative disorders.

Functional interaction of protein kinase CK2 and activating transcription factor 4 (ATF4), a key player in the cellular stress response

Protein kinase CK2 is a pleiotropic enzyme, which is implicated in the regulation of numerous biological processes. It seems to regulate the various functions by binding to other proteins and by phosphorylation of many different substrates. Here, we identified the activating transcription factor 4 (ATF4), an essential component of the ER stress signaling, as a new binding partner and a new substrate of CK2 in vitro and in vivo. Bifluorescence complementation analysis (BiFC) revealed that CK2α and ATF4 associate in the nucleus. By using mutants of ATF4 we identified serine 215 as the main CK2 phosphorylation site. The ATF4 S215A mutant turned out to be more stable than the wild-type form. We further noticed that an inhibition of CK2 caused an increased transcription of the ATF4 gene. Analyses of the transcription factor activity revealed an impaired activity of the CK2 phosphorylation mutant of ATF4. Thus, we show that (i) ATF4 is a binding partner of CK2α (ii) ATF4 is a substrate of CK2, (iii) the phosphorylation of ATF4 by CK2 influences the stability of ATF4, (iv) the transcription of ATF4 is regulated by CK2 and (v) the transcription factor activity of ATF4 is regulated by the CK2 phosphorylation of ATF4. Thus, CK2 plays an essential role in the regulation of the ER-stress induced signaling pathway.

Massive human co-expression network and its medical applications

Network-based analysis is indispensable in analyzing high-throughput biological data. Based on the assumption that the variation of gene interactions under given biological conditions could be better interpreted in the context of a large-scale and wide variety of developmental, tissue, and disease conditions, we leverage the large quantity of publicly available transcriptomic data >40,000 HG U133A Affymetrix microarray chips stored in ArrayExpress (http://www.ebi.ac.uk/arrayexpress/) using MetaOmGraph (http://metnet.vrac.iastate.edu/MetNet_MetaOmGraph.htm). From this data, 18,637 chips encompassing over 500 experiments containing high-quality data (18637 Hu-dataset) were used to create a globally stable gene co-expression network (18637 Hu-co-expression-network). Regulons, groups of highly and consistently co-expressed genes, were obtained by partitioning the 18637 Hu-co-expression-network using an Markov clustering algorithm (MCL). The regulons were demonstrated to be statistically significant using a gene ontology (GO) term overrepresentation test combined with evaluation of the effects of gene permutations. The regulons include ca. 12% of human genes, interconnected by 31,471 correlations. All network data and metadata are publically available (http://metnet.vrac.iastate.edu/MetNet_MetaOmGraph.htm). Text mining of these metadata, GO term overrepresentation analysis, and statistical analysis of transcriptomic experiments across multiple environmental, tissue, and disease conditions, has revealed novel fingerprints distinguishing central nervous system (CNS)-related conditions. This study demonstrates the value of mega-scale network-based analysis for biologists to further refine transcriptomic data, derived from a particular condition, to study the global relationships between genes and diseases, and to develop hypotheses that can inform future research.

Casein kinase 2 reverses tail-independent inactivation of kinesin-1

Kinesin-1 is a plus-end microtubule-based motor, and defects in kinesin-based transport are linked to diseases including neurodegeneration. Kinesin can auto-inhibit via a head-tail interaction, but is believed to be active otherwise. Here we report a tail-independent inactivation of kinesin, reversible by the disease-relevant signalling protein, casein kinase 2 (CK2). The majority of initially active kinesin (native or tail-less) loses its ability to interact with microtubules in vitro, and CK2 reverses this inactivation (approximately fourfold) without altering kinesin's single motor properties. This activation pathway does not require motor phosphorylation, and is independent of head-tail auto-inhibition. In cultured mammalian cells, reducing CK2 expression, but not its kinase activity, decreases the force required to stall lipid droplet transport, consistent with a decreased number of active kinesin motors. Our results provide the first direct evidence of a protein kinase upregulating kinesin-based transport, and suggest a novel pathway for regulating the activity of cargo-bound kinesin.

Protein kinase CK2 regulates the formation and clearance of aggresomes in response to stress

Misfolded protein aggregates elicit a stress response, and their clearance is crucial for cell survival. These aggregates are transported by cytoplasmic deacetylase HDAC6 and dynein motors to the aggresome via the microtubule network, and are removed by autophagic degradation. HDAC6 activity is necessary for both the transport and clearance of protein aggregates. However, the cellular factors that regulate HDAC6 activity remain unknown. Here we show that protein kinase CK2 is a crucial modulator of HDAC6 activity because CK2 directly phosphorylates HDAC6 and increases cytoplasmic deacetylase activity. Indeed, cells that expressed HDAC6 mutated at Ser458, a CK2-mediated phosphorylation site, failed to both form and clear aggresomes, and increased cytotoxicity. Interestingly, Ser458 is conserved only in higher primates, such as human and chimpanzee, but not in the rhesus macaque. These findings identify CK2 as a crucial protein involved in the formation and clearance of aggresomes, and hence in cell viability in response to misfolded protein stress.