Phosphorylation and dephosphorylation of Ca2+/calmodulin-dependent protein kinase kinase β at Thr144 in HeLa cells

Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ) acts as a regulatory kinase that phosphorylates and activates multiple downstream kinases including CaMKI, CaMKIV, 5′AMP-activated protein kinase (AMPK) and protein kinase B (PKB), resulting in regulation of wide variety of Ca2+-dependent physiological responses under normal and pathological conditions. CaMKKβ is regulated by Ca2+/calmodulin-binding, autophosphorylation, and transphosphorylation by multiple protein kinases including cAMP-dependent protein kinase (PKA). In this report, we found that phosphorylation of CaMKKβ is dynamically regulated by protein phosphatase/kinase system in HeLa cells. Global phosphoproteomic analysis revealed the constitutive phosphorylation at 8 Ser residues including Ser128, 132, and 136 in the N-terminal regulatory domain of rat CaMKKβ in unstimulated HeLa cells as well as inducible phosphorylation of Thr144 in the cells treated with a phosphatase inhibitor, okadaic acid (OA). Thr144 phosphorylation in CaMKKβ has shown to be rapidly induced by OA treatment in a time- and dose-dependent manner in transfected HeLa cells, indicating that Thr144 in CaMKKβ is maintained unphosphorylated state by protein phosphatase(s). We confirmed that in vitro dephosphorylation of pThr144 in CaMKKβ by protein phosphatase 2A and 1. We also found that the pharmacological inhibition of protein phosphatase(s) significantly induces CaMKKβ-phosphorylating activity (at Thr144) in HeLa cell lysates as well as in intact cells; however, it was unlikely that this activity was catalyzed by previously identified Thr144-kinases, such as AMPK and PKA. Taken together, these results suggest that the phosphorylation and dephosphorylation of Thr144 in CaMKKβ is dynamically regulated by multiple kinases/phosphatases signaling resulting in fine-tuning of the enzymatic property

Regulation of Ca2+/calmodulin-dependent protein kinase kinase beta by cAMP signaling

BACKGROUND: Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) is a pivotal activator of CaMKI, CaMKIV and 5'-AMP-activated protein kinase (AMPK), controlling Ca2+-dependent intracellular signaling including various neuronal, metabolic and pathophysiological responses. Recently, we demonstrated that CaMKKβ is feedback phosphorylated at Thr144 by the downstream AMPK, resulting in the conversion of CaMKKβ into Ca2+/CaM-dependent enzyme. However, the regulatory phosphorylation of CaMKKβ at Thr144 in intact cells and in vivo remains unclear. METHODS: Anti-phosphoThr144 antibody was used to characterize the site-specific phosphorylation of CaMKKβ in immunoprecipitated samples from mouse cerebellum and in transfected mammalian cells that were treated with various agonists and protein kinase inhibitors. CaMKK activity assay and LC-MS/MS analysis were used for biochemical characterization of phosphorylated CaMKKβ. RESULTS: Our data suggest that the phosphorylation of Thr144 in CaMKKβ is rapidly induced by cAMP/cAMP-dependent protein kinase (PKA) signaling in CaMKKβ-transfected HeLa cells, that is physiologically relevant in mouse cerebellum. We confirmed that the catalytic subunit of PKA was capable of directly phosphorylating CaMKKβ at Thr144 in vitro and in transfected cells. In addition, the basal phosphorylation of CaMKKβ at Thr144 in transfected HeLa cells was suppressed by AMPK inhibitor (compound C). PKA-catalyzed phosphorylation reduced the autonomous activity of CaMKKβ in vitro without significant effect on the Ca2+/CaM-dependent activity, resulting in the conversion of CaMKKβ into Ca2+/CaM-dependent enzyme. CONCLUSION: cAMP/PKA signaling may confer Ca2+-dependency to the CaMKKβ-mediated signaling pathway through direct phosphorylation of Thr144 in intact cells. GENERAL SIGNIFICANCE: Our results suggest a novel cross-talk between cAMP/PKA and Ca2+/CaM/CaMKKβ signaling through regulatory phosphorylation

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

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

Regulation of the tubulin polymerization-promoting protein by Ca2+/S100 proteins

To elucidate S100 protein-mediated signaling pathways, we attempted to identify novel binding partners for S100A2 by screening protein arrays carrying 19,676 recombinant glutathione S-transferase (GST)-fused human proteins with biotinylated S100A2. Among newly discovered putative S100A2 interactants, including TMLHE, TRH, RPL36, MRPS34, CDR2L, OIP5, and MED29, we identified and characterized the tubulin polymerization-promoting protein (TPPP) as a novel S100A2-binding protein. We confirmed the interaction of TPPP with Ca2+/S100A2 by multiple independent methods, including the protein array method, S100A2 overlay, and pulldown assay in vitro and in transfected COS-7 cells. Based on the results from the S100A2 overlay assay using various GST-TPPP mutants, the S100A2-binding region was identified in the C-terminal (residues 111-160) of the central core domain of a monomeric form of TPPP that is involved in TPPP dimerization. Chemical cross-linking experiments indicated that S100A2 suppresses dimer formation of His-tagged TPPP in a dosedependent and a Ca2+-dependent manner. In addition to S100A2, TPPP dimerization is disrupted by other multiple S100 proteins, including S100A6 and S100B, in a Ca2+-dependent manner but not by S100A4. This is consistent with the fact that S100A6 and S100B, but not S100A4, are capable of interacting with GST-TPPP in the presence of Ca2+. Considering these results together, TPPP was identified as a novel target for S100A2, and it is a potential binding target for other multiple S100 proteins, including S100A6 and S100B. Direct binding of the S100 proteins with TPPP may cause disassembly of TPPP dimer formation in response to the increasing concentration of intracellular Ca2+, thus resulting in the regulation of the physiological function of TPPP, such as microtubule organization

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TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

E-Cadherin Promotes Incorporation of Mouse Epiblast Stem Cells into Normal Development

<div><p>Mouse epiblast stem cells (mEpiSCs) are pluripotent stem cells derived from epiblasts of postimplantation mouse embryos. Their pluripotency is distinct from that of mouse embryonic stem cells (mESCs) in several cell biological criteria. One of the distinctions is that mEpiSCs contribute either not at all or at much lower efficiency to chimeric embryos after blastocyst injection compared to mESCs. However, here we showed that mEpiSCs can be incorporated into normal development after blastocyst injection by forced expression of the E-cadherin transgene for 2 days in culture. Using this strategy, mEpiSCs gave rise to live-born chimeras from 5% of the manipulated blastocysts. There were no obvious signs of reprogramming of mEpiSCs toward the mESC-like state during the 2 days after induction of the E-cadherin transgene, suggesting that mEpiSCs possess latent ability to integrate into the normal developmental process as its origin, epiblasts.</p> </div

Efficiency of chimera generation from EpiSCs with (+Dox) or without (–Dox) E-cadherin induction.

<p>To evaluate 24-h survival rate of injected EpiSCs, injected blastocysts were randomly picked followed by microscopic observation of EGFP-positive EpiSCs. Remaining injected blastocysts were transferred into the uterus of a pseudopregnant ICR female. At 13.5E, mice were sacrificed to collect embryos to evaluate chimerism of the injected EpiSC. ESCs were used as a control to determine chimerism.</p

Establishment of mEpiSC lines carrying the doxycycline-inducible <i>E-cadherin</i> transgene.

<p>A) Time schedule of all experiments with doxycycline (Dox)-inducible expression of E-cadherin in mEpiSCs. mEpiSCs were plated on fibronectin-coated dishes followed by incubation for 24 h, and <i>E-cadherin</i> was induced by addition of doxycycline for 2 days. Then, mEpiSCs were dissociated into single-cell suspensions and were subjected to later experiments, such as blastocyst injection, Western blotting, and qPCR analysis. B) qPCR analysis of <i>E-cadherin</i> inducible mEpiSCs (EIN3 and EIN6) cultured with or without doxycycline as described in A. The level of expression of each transcript in parental mEpiSCs (PTmEpiSCs) was defined as 1.0. The expression levels in EB5 ES cells cultured with or without the MEF feeder layer (EB5^MEF and EB5) are also shown. C) Western blotting analyses for E-cadherin, Oct3/4, and Nanog expression in EB5 ES cells (ESC), EIN6 transgenic mEpiSCs cultured with or without doxycycline for 2 days (EIN6 and +Dox), EIN6 mEpiSCs cultured with doxycycline for 2 days followed by culture without doxycycline for 1 or 2 days (–d1 and –d2). CDK2 is shown as a loading control. D) Quantitative analysis of E-cadherin expression level in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045220#pone-0045220-g001" target="_blank">Figure 1C</a>. E-cadherin protein levels were normalized to that of Oct3/4 protein in each sample and the level in ESC was defined as 1.0. E) FACS analysis of E-cadherin expression level in EIN6 mEpiSCs cultured with (blue line) or without (red line) doxycycline for 2 days.</p