1,721,046 research outputs found
Signaling specificity in the Akt pathway in biology and disease
No full textAkt/PKB is a key master regulator of a wide range of physiological functions including metabolism, proliferation, survival, growth, angiogenesis and migration and invasion. The Akt protein kinase family comprises three highly related isoforms encoded by different genes. The initial observation that the Akt isoforms share upstream activators as well as several downstream effectors, together with the high sequence homology suggested that their functions were mostly redundant. By contrast, an increasing body of evidence has recently uncovered the concept of Akt isoform signaling specificity, supported by distinct phenotypes displayed by animal strains genetically modified for each of the three genes, as well as by the identification of isoform-specific substrates and association with discrete subcellular locations. Given that Akt is regarded as a promising therapeutic target in a number of pathologies, it is essential to dissect the relative contributions of each isoform, as well as the degree of compensation in pathophysiological function. Here we summarize our view of how Akt selectivity is achieved in the context of subcellular localization, isoform-specific substrate phosphorylation and context-dependent functions in normal and pathophysiological settings
Nuclear redox control of stem cell ageing
No full textMesenchymal stem cells (MSCs) have emerged as an important tool that can be used for drug screening, disease
modeling and tissue regeneration thanks to their easy preparation, differentiation potential and immunomodulatory
activity.
A redox imbalance, due to extensive culture of stem cells in vitro prior to clinical use, can lead to oxidative stress.
However, oxidative stress is known to play an important role in modulating different stem cells properties, such as
self-renewal, proliferation, differentiation and senescence. A specific source of reactive oxygen species, the NADPH
oxidase isoform 4 (Nox4), can localize also into the nuclei where it can have an impact on the regulation of crucial
stemness-related genes. Moreover, the accumulation in human MSCs’ nuclei of the nuclear lamina precursor,
prelamin A, gives rise to a premature aging phenotype that ultimately causes reduced functionality of these cells in
vivo.
The aim of the study was to investigate the aging process occurring during in vitro expansion of human fetal
MSCs, obtained from amniotic fluid at similar gestational age. This process is certainly influenced by the oxidative
stress exposure implied in extensive culture, but could be also donor dependent. The analysis of 15 AFSC samples
allowed to classify them in groups with different levels of stemness properties evident even since the first passages
in culture. In summary, the expression of Oct-4, a pluripotency gene, and proliferation rate are inversely correlated
to the presence of the nuclear form of Nox4, the content of reactive oxygen species, DNA damage signs and the
onset of senescence and premature aging markers, including accumulation of prelamin A, p21 and p16. Indeed,
coimmunoprecipitation experiments demonstrated an interaction between prelamin A and Nox4, suggesting an
interplay of these proteins in modulating the maintenance of stemness properties
Phosphorylation, Signaling, and Cancer: Targets and Targeting
Full text linkAfter 60 years from the first report of an enzymatic phosphorylation of proteins, protein kinases are well-established key signaling molecules that impact all major biological processes (reviewed in [1, 2]). Protein and lipid kinases fulfill essential roles in many signaling pathways that regulate normal cell functions [1–5]. Deregulation of kinase activities leads to a variety of pathologies ranging from cancer to inflammatory diseases, diabetes, infectious diseases, cardiovascular disorders, and cell growth and survival [1, 2, 5–11]. A much larger proportion of additional kinases are present in parasites and bacterial, fungal, and viral genomes that are susceptible to exploitation as drug targets [12]. Since many human diseases result from overactivation of protein and lipid kinases due to mutations and/or overexpression, this enzyme class represents an important target for the pharmaceutical industry [6]. Approximately one-third of all protein targets under investigation in the pharmaceutical industry are protein or lipid kinases and to date 33 small molecular weight kinase inhibitors (SMWKIs) and a handful of therapeutic antibodies have been approved for various indications mainly in oncology and many more in various stages of clinical and preclinical development [5]. Kinase inhibitor drugs, which are in clinical trials, target all stages of signal transduction from the receptor protein tyrosine kinases that initiate intracellular signaling, through second-messenger dependent lipid and protein kinases and protein kinases that regulate the cell cycle [10, 13]. While treating chronic phase CML (an almost monogenic disease) with imatinib has been very successful, the treatment of more advanced cancers with kinase inhibitors has proven more difficult due to the heterogeneity of these cancer types as well as due to kinase inhibitor resistance resulting from selection for mutant alleles and/or upregulation of alternative signaling pathways [5, 10]
Cross-talk between the CK2 and AKT signaling pathways in cancer
No full textCK2 and AKT display a high degree of cross-regulation of their respective functions, both directly, through physical interaction and phosphorylation, and indirectly, through an intense cross-talk of key downstream effectors, ultimately leading to sustained AKT activation.Being CK2 and AKT attractive targets for therapeutic intervention, here we would like to emphasize how AKT and CK2 might influence cell fate through their complex isoform-specific and contextual-dependent cross-talk, to the extent that such functional interplay should be considered when devising therapies that target one or both these key signaling kinases
Interleukin-1alfa stimulates nuclear phosphoinositidase C activity in human osteosarcoma SaOS-2 cells.
No full textInterleukin-1alfa stimulates nuclear phosphoinositidase C activity in human osteosarcoma SaOS-2 cell
Interleukin-1-receptor-associated kinase 2 (IRAK2)-mediated interleukin-1-dependent nuclear factor kappa B transactivation in Saos2 cells requires the Akt/protein kinase B kinase
No full textThe post-receptor pathway that leads to nuclear factor kappaB (NF-kappaB) activation begins with the assembly of a membrane-proximal complex among the interleukin 1 (IL-1) receptors and the adaptor molecules, myeloid differentiation protein 88 (MyD88), IL-1-receptor-associated kinases (IRAKs) and tumour-necrosis-factor-receptor-associated factor 6. Eventually, phosphorylation of the inhibitor of NF-kappaB (IkappaB) by the IkappaB kinases releases NF-kappaB, which translocates to the nucleus and modulates gene expression. In this paper, we report that IRAK2 and MyD88, but not IRAK1, interact physically with Akt, as demonstrated by coimmunoprecipitation and pull-down experiments. Interestingly, the association of Akt with recombinant IRAK2 is decreased by stimulation with IL-1, and is favoured by pre-treatment with phosphatase. Likewise, Akt association with IRAK2 is increased considerably by overexpression of PTEN (phosphatase and tensin homologue deleted on chromosome 10), while it is completely abrogated by overexpression of phosphoinositide-dependent protein kinase 1. These data indicate that Akt takes part in the formation of the signalling complex that conveys the signal from the IL-1 receptors to NF-kappaB, a step that is much more membrane-proximal than was reported previously. We also demonstrate that Akt activity is necessary for IL-1-dependent NF-kappaB transactivation, since a kinase-defective mutant of Akt impairs IRAK2- and MyD88-dependent, but not IRAK1-dependent, NF-kappaB activity, as monitored by a gene reporter assay. Accordingly, IRAK2 failed to trigger inducible nitric oxide synthase and IL-1beta production in cells expressing dominant-negative Akt. However, NF-kappaB binding to DNA was not affected by inhibition of Akt, indicating that Akt regulates NF-kappaB at a level distinct from the dissociation of p65 from IkappaBalpha and its translocation to the nucleus, possibly involving phosphorylation of the p65 transactivation domain
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Pharmacological inhibition of protein kinase CK2 reverts the multidrug resistance phenotype of a CEM cell line characterized by high CK2 level
No full textProtein kinase CK2 is an ubiquitous and constitutively active kinase, which phosphorylates many cellular proteins and is implicated in the regulation of cell survival, proliferation and transformation. We investigated its possible involvement in the multidrug resistance phenotype (MDR) by analysing its level in two variants of CEM cells, namely S-CEM and R.-CEM, normally sensitive or resistant to chemical apoptosis, respectively. We found that, while the CK2 regulatory subunit beta was equally expressed in the two cell variants, CK2 alpha catalytic subunit was higher in R-CEM and this was accompanied by a higher phosphorylation of endogenous protein substrates. Pharmacological downregulation of CK2 activity by a panel of specific inhibitors, or knockdown of CK2 alpha expression by RNA interference, were able to induce cell death in R-CEM. CK2 inhibitors could promote an increased uptake of chemotherapeutic drugs inside the cells and sensitize them to drug-induced apoptosis in a co-operative manner. CK2 blockade was also effective in inducing cell death of a different MDR line (U2OS). We therefore conclude that inhibition of CK2 can be considered as a promising tool to revert the MDR phenotype
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