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Abstract: Reactive gliosis has been implicated in both inflammatory and neurodegenerative diseases. However, mechanisms by which astrocytic activation affects synaptic efficacy have been poorly elucidated. We have used the spared nerve injury (SNI) of the sciatic nerve to induce reactive astrocytosis in the lumbar spinal cord and investigate its potential role in disrupting the neuro-glial circuitry. Analysis of spinal cord sections revealed that SNI was associated with an increase of microglial (Iba1) and astrocytic (GFAP) markers. These changes, indicative of reactive gliosis, were paralleled by (i) a decrease of glial amino acid transporters (GLT1 and GlyT1) and increased levels of (ii) neuronal glutamate transporter EAAC1, (iii) neuronal vesicular GABA transporter (vGAT) and (iv) the GABAergic neuron marker GAD65/67. Besides the increase of Glutamate/GABA ratio, indicative of the perturbation of synaptic circuitry homeostasis, the boost of glutamate also compromised glial function in neuroprotection by up-regulating the xCT subunit of the glutamate-cystine antiport system and reducing glutathione (GSH) production. Finally, this study also shows that all these structural changes were linked to an alteration of endogenous NGF metabolism, as demonstrated by the decrease of endogenous NGF expression levels and increased activity of the NGF-degrading metalloproteinases. All the changes displayed by SNI-animals were reversed by a 7-days i.t. administration of NGF or GM6001, a generic metalloproteinase inhibitor, as compared to vehicle (ACSF)-treated animals. All together, these data strongly support the correlation between reactive astrogliosis and mechanisms underlying the perturbation of the synaptic circuitry in the SNI model of peripheral nerve injury, and the essential role of NGF in restoring both synaptic homeostasis and the neuroprotective function of glia. [Copyright &y& Elsevier]

Abstract: CK2 is a highly conserved protein kinase controlling different cellular processes. It shows a higher activity in proliferating mammalian cells, in various types of cancer cell lines and tumors. The findings presented herein provide the first evidence of an in vivo modulation of CK2 activity, dependent on growth rate, in Saccharomyces cerevisiae. In fact, CK2 activity, assayed on nuclear extracts, is shown to increase in exponential growing batch cultures at faster growth rate, while localization of catalytic and regulatory subunits is not nutritionally modulated. Differences in intracellular CK2 activity of glucose- and ethanol-grown cells appear to depend on both increase in molecule number and k cat. Also in chemostat cultures nuclear CK2 activity is higher in faster growing cells providing the first unequivocal demonstration that growth rate itself can affect CK2 activity in a eukaryotic organism. [Copyright &y& Elsevier]

Abstract: Large-scale “omics” data are often represented as networks of interacting components, but such representation is inherently static and, as such, cannot provide a realistic picture of the temporal dynamics of complex cellular functions. These difficulties suggest moving to a modeling strategy that explicitly takes into account both the wiring of the components and the task they perform. From an engineering perspective, this problem resembles that of “circuit analysis”. In this paper, we focus on a limited but relevant biological circuit, the G1 to S transition in yeast cell cycle, and investigate both the network representation and the corresponding circuit described by a mathematical model, by means of a wide range of numerical simulation analysis. Reliable predictions of system-level properties are achieved and the parameters that mostly affect these properties are found out. [Copyright &y& Elsevier]

Abstract: Protein kinase CK2 is a heterotetramer composed of two catalytic and two regulatory subunits. In Saccharomyces cerevisiae the catalytic subunits (α and α′) are encoded by the CKA1, CKA2 genes. cka1Δcka2ts mutants arrest cell cycle in both G1 and G2/M at 37°C. Hence, it has been proposed that CK2 plays an important role in cell-cycle progression and several cell-cycle proteins have been reported to be CK2 substrates. We have previously shown that Sic1, the inhibitor of Clb5–Cdc28 complexes required for the G1/S transition, is a physiologically relevant CK2 substrate. Here we show that CK2 inactivation up-regulates Sic1 level resulting in severe down-regulation of Clb5–Cdc28 kinase activity. Concurrent inactivation of Sic1 and CK2 leads to accumulation of cells with a post-synthetic DNA content and short/elongated spindles, typical of cells arrested in mitosis. These findings indicate that Sic1 plays a major role during G1 arrest of CK2-inactivated cells. [Copyright &y& Elsevier]

Abstract: We have previously identified Ser201 of Sic1, a yeast cyclin-dependent kinase inhibitor, as an in vitro target of protein kinase CK2. Here we present new evidence, by using specific anti-P-Ser201 antibodies and 2-D gel electrophoresis coupled to MALDI mass spectrometry analysis, that Sic1 is phosphorylated in vivo on Ser201 shortly after its de novo synthesis, during late anaphase in glucose-grown cells. This phosphorylation is also detected in Sic1 immunopurified from G1 cells. In agreement with these data we also show that the catalytic α′ subunit of CK2, whose function is required for cell cycle progression, is detected in Sic1 immunopurified complexes, and that phosphorylation on Ser201 is reduced after CK2 inactivation at the non-permissive temperature in a cka1Δcka2 ts yeast strain. These data strongly support the notion that CK2 phosphorylates Sic1 in vivo. [Copyright &y& Elsevier]

Abstract: We have previously demonstrated that the cyclin-dependent kinase inhibitor (Cki) Sic1 of Saccharomyces cerevisiae is phosphorylated in vitro by the CK2 kinase on Ser201 residue. Moreover, we have collected evidence showing that Sic1 is functionally and structurally related to mammalian Cki p27Kip1 and binds to the mammalian Cdk2/cyclin A complex with a similar mode of inhibition. In this paper, we use SPR analysis to investigate the binding of Sic1 to the catatytic and regulatory subunits of CK2. Evidence is presented showing that phosphorylation of Sic1 at the CK2 consensus site QES201EDEED increases the binding of a Sic1-derived peptide to the Cdk2/cyclin A complex, a functional homologue of the yeast Cdk1/Clb5,6. Moreover, Sic1 fully phosphorylated in vitro on Ser201 by CK2 is shown to be a stronger inhibitor of the Cdk/cyclin complexes than the unphosphorylated protein. Taken together, these data disclose the possibility that CK2 plays a role in the regulation of Sic1 activity. [Copyright &y& Elsevier]