The protein kinase CK2 catalytic domain from Plasmodium falciparum: crystal structure, tyrosine kinase activity and inhibition.

Malaria causes every year over half-a-million deaths. The emergence of parasites resistant to available treatments makes the identification of new targets and their inhibitors an urgent task for the development of novel anti-malaria drugs. Protein kinase CK2 is an evolutionary-conserved eukaryotic serine/threonine protein kinase that in Plasmodium falciparum (PfCK2) has been characterized as a promising target for chemotherapeutic intervention against malaria.

TAK1, more than just innate immunity.

Transforming growth factor β-activated kinase 1 (TAK1) is a key regulator of the innate immunity and the proinflammatory signaling pathway. In response to interleukin-1, tumor necrosis factor-α, and toll-like receptor agonists, it mediates the activation of the nuclear factor κB (NF-κB), c-Jun N-terminal kinase (JNK), and p38 pathways. In addition, TAK1 plays a central role in adaptive immunity, in which it mediates signaling from T- and B-cell receptors.

Pellino1 is required for interferon production by viral double-stranded RNA.

Viral double-stranded RNA, a ligand for Toll-like Receptor 3 (TLR3) and the cytoplasmic RNA receptors RIG1 and MDA5, activate a signaling network in which the IKK-related protein kinase TBK1 phosphorylates the transcription factor Interferon Regulatory Factor 3 (IRF3) and the E3 ubiquitin ligase Pellino1. IRF3 then translocates to the nucleus where it stimulates transcription of the interferonβ (IFNβ) gene, but the function of Pellino1 in this pathway is unknown. Here, we report that myeloid cells and embryonic fibroblasts from knock-in mice expressing an E3 ligase-deficient mutant of Pellino1 produce reduced levels of IFNβ mRNA and secrete much less IFNβ in response to viral double-stranded RNA because the interaction of IRF3 with the IFNβ promoter is impaired.

Activation of type I and III interferon signalling pathways occurs in lung epithelial cells infected with low pathogenic avian influenza viruses.

The host response to the low pathogenic avian influenza (LPAI) H5N2, H5N3 and H9N2 viruses were examined in A549, MDCK, and CEF cells using a systems-based approach. The H5N2 and H5N3 viruses replicated efficiently in A549 and MDCK cells, while the H9N2 virus replicated least efficiently in these cell types. However, all LPAI viruses exhibited similar and higher replication efficiencies in CEF cells.

Identification of the protein kinases that activate the E3 ubiquitin ligase Pellino 1 in the innate immune system.

The E3 ubiquitin ligase Pellino 1 can be interconverted between inactive and active forms by a reversible phosphorylation mechanism. In vitro, phosphorylation and activation can be catalysed by either the IRAKs [IL (interleukin)-1-receptor-associated kinases] IRAK1 and IRAK4, or the IKK {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase}-related kinases [IKKϵ and TBK1 (TANK {TRAF [TNF (tumour-necrosis-factor)-receptor-associated factor]-associated NF-κB activator}-binding kinase 1)]. In the present study we establish that IRAK1 is the major protein kinase that mediates the IL-1-stimulated activation of Pellino 1 in MEFs (mouse embryonic fibroblasts) or HEK (human embryonic kidney)-293 cells, whereas the IKK-related kinases activate Pellino 1 in TNFα-stimulated MEFs.

The role of TBK1 and IKKε in the expression and activation of Pellino 1.

Mammalian Pellino isoforms are phosphorylated by IRAK (interleukin receptor associated kinase) 1/IRAK4 in vitro, converting them into active E3 ubiquitin ligases. In the present paper we report a striking enhancement in both transcription of the gene encoding Pellino 1 and Pellino 1 protein expression when murine BMDMs (bone-marrow-derived macrophages) are stimulated with LPS (lipopolysaccharide) or poly(I:C). This induction occurs via a TRIF [TIR (Toll/interleukin-1 receptor)-domain-containing adaptor-inducing interferon-β]-dependent IRAK-independent pathway and is prevented by inhibition of the IKK [IκB (inhibitor of nuclear factor κB) kinase]-related protein kinases, TBK1 {TANK [TRAF (tumour-necrosis-factor-receptor-associated factor)-associated nuclear factor κB activator]-binding kinase 1} and IKKε.

Autoactivation of transforming growth factor beta-activated kinase 1 is a sequential bimolecular process.

Transforming growth factor-beta-activated kinase 1 (TAK1), an MAP3K, is a key player in processing a multitude of inflammatory stimuli. TAK1 autoactivation involves the interplay with TAK1-binding proteins (TAB), e.g.

Regulation of cell proliferation and migration by TAK1 via transcriptional control of von Hippel-Lindau tumor suppressor.

Skin maintenance and healing after wounding requires complex epithelial-mesenchymal interactions purportedly mediated by growth factors and cytokines. We show here that, for wound healing, transforming growth factor-beta-activated kinase 1 (TAK1) in keratinocytes activates von Hippel-Lindau tumor suppressor expression, which in turn represses the expression of platelet-derived growth factor-B (PDGF-B), integrin beta1, and integrin beta5 via inhibition of the Sp1-mediated signaling pathway in the keratinocytes. The reduced production of PDGF-B leads to a paracrine-decreased expression of hepatocyte growth factor in the underlying fibroblasts.

HSP90 is required for TAK1 stability but not for its activation in the pro-inflammatory signaling pathway.

The protein kinase transforming-growth-factor-beta-activated kinase-1 (TAK1) is a key regulator in the pro-inflammatory signaling pathway and is activated by tumor necrosis factor-alpha, interleukin-1 (IL-1) and lipopolysaccharide (LPS). We describe the identification of TAK1 as a client protein of the 90 kDa heat-shock protein (Hsp90)/cell division cycle protein 37 (Cdc37) chaperones. However, Hsp90 is not required for the activation of TAK1 as short exposure to the Hsp90 inhibitor, 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) did not affect its activation by LPS or IL-1.

A new p38 MAP kinase-regulated transcriptional coactivator that stimulates p53-dependent apoptosis.

The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in stress-induced cell-fate decisions by orchestrating responses that go from cell-cycle arrest to apoptosis. We have identified a new p38 MAPK-regulated protein that we named p18(Hamlet), which becomes stabilized and accumulates in response to certain genotoxic stresses such as UV or cisplatin treatment. Overexpression of p18(Hamlet) is sufficient to induce apoptosis, whereas its downregulation reduces the apoptotic response to these DNA damage-inducing agents.

TAB3, a new binding partner of the protein kinase TAK1.

We have identified a new binding partner of the TGFbeta (transforming growth factor-beta)-activated protein kinase (TAK1), termed TAB3 (TAK1-binding protein-3), which shares 48% amino acid sequence identity with TAB2. Our results indicate that two distinct TAK1 complexes are present in cells. One comprises TAK1 complexed with TAB1 and TAB2, and the other TAK1 complexed with TAB1 and TAB3.

Feedback control of the protein kinase TAK1 by SAPK2a/p38alpha.

TAB1, a subunit of the kinase TAK1, was phosphorylated by SAPK2a/p38alpha at Ser423, Thr431 and Ser438 in vitro. TAB1 became phosphorylated at all three sites when cells were exposed to cellular stresses, or stimulated with tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) or lipopolysaccharide (LPS). The phosphorylation of Ser423 and Thr431 was prevented if cells were pre-incubated with SB 203580, while the phosphorylation of Ser438 was partially inhibited by PD 184352.

Evidence that the tandem-pleckstrin-homology-domain-containing protein TAPP1 interacts with Ptd(3,4)P2 and the multi-PDZ-domain-containing protein MUPP1 in vivo.

PtdIns(3,4,5)P3 is an established second messenger of growth-factor and insulin-induced signalling pathways. There is increasing evidence that one of the immediate breakdown products of PtdIns(3,4,5)P3, namely PtdIns(3,4)P2, whose levels are elevated by numerous extracellular agonists, might also function as a signalling molecule. Recently, we identified two related pleckstrin-homology (PH)-domain-containing proteins, termed 'tandem-PH-domain-containing protein-1' (TAPP1) and TAPP2, which interacted in vitro with high affinity with PtdIns(3,4)P2, but did not bind PtdIns(3,4,5)P3 or other phosphoinositides.