Descripción: Initially, memory is labile and requires consolidation to become stable. However, several studies support that consolidated memories can undergo a new period of lability after retrieval. The mechanistic differences of this process, termed reconsolidation, with the consolidation process are under debate, including the participation of hippocampus. Up to this point, few reports describe molecular changes and, in particular, transcription factor (TF) involvement in memory restabilization. Increasing evidence supports the participation of the TF nuclear factor-κB (NF-κB) in memory consolidation. Here, we demonstrate that the inhibition of NF-κB after memory reactivation impairs retention of a hippocampal-dependent inhibitory avoidance task in mice. We used two independent disruptive strategies to reach this conclusion. First, we administered intracerebroventricular or intrahippocampal sulfasalazine, an inhibitor of IKK (IκB kinase), the kinase that activates NF-κB. Second, we infused intracerebroventricular or intrahippocampal κB decoy, a direct inhibitor of NF-κB consisting of a double-stranded DNA oligonucleotide that contains the κB consensus sequence. When injected immediately after memory retrieval, sulfasalazine or κB decoy (Decoy) impaired long-term retention. In contrast, a one base mutated κB decoy (mDecoy) had no effect. Furthermore, we also found NF-κB activation in the hippocampus, with a peak 15 min after memory retrieval. This activation was earlier than that found during consolidation. Together, these results indicate that NF-κB is an important transcriptional regulator in memory consolidation and reconsolidation in hippocampus, although the temporal kinetics of activation differs between the two processes. Copyright © 2007 Society for Neuroscience.

Descripción: It has been shown that the molecular mechanism by which cytokines and glucocorticoids mutually antagonize their functions involves a mutual glucocorticoid receptor (GR)/nuclear factor-κB (NF-κB) transrepression. Here we report a role for the nuclear receptor coactivator RAC3, in modulating NF-κB transactivation. We found that RAC3 functions as a coactivator by binding to the active form of NF-κB and that overexpression of RAC3 restores GR-dependent transcription neglecting GR/NF-κB transrepression. The competition between GR and NF-κB for binding to RAC3 may represent a general mechanism by which both transcription factors mutually antagonize their activity. (C) 2000 Federation of European Biochemical Societies.

Descripción: Several studies support that stored memories undergo a new period of consolidation after retrieval. It is not known whether this process, termed reconsolidation, requires the same transcriptional mechanisms involved in consolidation. Increasing evidence supports the participation of the transcription factor NF-κB in memory. This was initially demonstrated in the crab Chasmagnathus model of associative contextual memory, in which re-exposure to the training context induces a well characterized reconsolidation process. Here we studied the role of NF-κB in reconsolidation. NF-κB was specifically activated in trained animals re-exposed to the training context but not to a different context. NF-κB was not activated when animals were re-exposed to the context after a weak training protocol insufficient to induce long-term memory. A specific inhibitor of the NF-κB pathway, sulfasalazine, impaired reconsolidation when administered 20 min before re-exposure to the training context but was not effective when a different context was used. These findings indicate for the first time that NF-κB is activated specifically by retrieval and that this activation is required for memory reconsolidation, supporting the view that this molecular mechanism is required in both consolidation and reconsolidation.

Descripción: The cellular resistance to tumor necrosis factor (TNF) of most cell types has been attributed to both a protective pathway induced by this cytokine and the preexistence of protective factors in the target cell. NF-κB has been postulated as one of the principal factors involved in antiapoptotic gene expression control on TNF-resistant cells. We have previously shown that glucocorticoids protect the naturally TNF-sensitive L-929 cells from apoptosis. Here we analyze the role of NF-κB and glucocorticoids on TNF-induced apoptosis in L-929 cells. We found that inhibition of NF-κB enhanced the sensitivity to TNF-induced apoptosis. Glucocorticoids inhibited NF-κB transactivation via IκB induction. Moreover, glucocorticoids protected from TNF-induced apoptosis even when NF-κB activity was inhibited by stable or transient expression of the superrepressor IκB. These results demonstrate that although glucocorticoids inhibit NF-κB transactivation in these cells, this is not required for their protection from TNF-induced apoptosis. (C) 2000 Elsevier Science B.V.

Descripción: In contextual memories, an association between a positive or negative reinforcement and the contextual cues where the reinforcement occurs is formed. The re-exposure to the context without reinforcement can lead to memory extinction or reconsolidation, depending on the number of events or duration of a single event of context re-exposure. Extinction involves the temporary waning of the previously acquired conditioned response. The molecular processes underlying extinction and the mechanisms which determine if memory will reconsolidate or extinguish after retrieval are not well characterized, particularly the role of transcription factors and gene expression. Here we studied the participation of a transcription factor, NF-κB, in memory extinction. In the crab context-signal memory, the activation of NF-κB plays a critical role in consolidation and reconsolidation, memory processes that are well characterized in this model. The administration of a NF-κB inhibitor, sulfasalazine prior to extinction session impeded spontaneous recovery. Moreover, reinstatement experiments showed that the original memory was not affected and that NF-κB inhibition by sulfasalazine impaired spontaneous recovery strengthening the ongoing memory extinction process. Interestingly, in animals with fully consolidated memory, a brief re-exposure to the training context induced neuronal NF-κB activation and reconsolidation, while prolonged re-exposure induced NF-κB inhibition and memory extinction. These data constitutes a novel insight into the molecular mechanisms involved in the switch between memory reconsolidation and extinction. Moreover, we propose the inhibition of NF-κB as the engaged mechanism underlying extinction, supporting a novel approach for the pharmacological enhancement of this memory process. The accurate description of the molecular mechanisms that support memory extinction is potentially useful for developing new strategies and drug candidates for therapeutic treatments of the maladaptive memory disorders such as post-traumatic stress, phobias, and drug addiction. © 2008 Merlo, Romano.

Descripción: Several studies indicate that hyaluronan oligosaccharides (oHA) are able to modulate growth and cell survival in solid tumors; however, no studies have been undertaken to analyze the effect of oHA on T-lymphoid disorders. In this work we showed that oHA were able to induce apoptosis in lymphoma cell lines. Since PI3-K/Akt and nuclear factor-κB (NF-κB) are major factors involved in cell survival and anti-apoptotic pathways in lymphoma cells, we hypothesized that oHA could induce apoptosis through inhibition of these pathways. oHA were identified by a method which allows characterization of length using a high pH anion exchange chromatography with pulse amperometric detection (HPAEC-PAD). oHA inhibited PIP3 production (principal product of PI3-K activity) and reduced Akt phosphorylation levels, similarly to the specific inhibitor wortmannin. However, treatment with either oHA or wortmannin failed to inhibit constitutive NF-κB activity and modulate IκBα protein levels, suggesting that PI3-K and NF-κB signaling pathways are not related in the cell lines used. Cell behavior differed using native hyaluronan (HA), which induced PIP3 production, Akt phosphorylation, and NF-κB activation, although not related with cell survival since treatment with native HA showed no effect on apoptosis. Our results suggest that oHA induce apoptosis by suppression of PI3-K/Akt cell survival pathway without involving NF-κB activation, through a mechanism that differs from the one mediated by native HA. © 2006 Oxford University Press.

Descripción: Despite considerable progress in our understanding of the interplay between immune and endocrine systems, the role of thyroid hormones and their receptors in the control of adaptive immunity is still uncertain. Here, we investigated the role of thyroid hormone receptor (TR) β 1 signaling in modulating dendritic cell (DC) physiology and the intracellular mechanisms underlying these immunoregulatory effects. Exposure of DCs to triiodothyronine (T 3 ) resulted in a rapid and sustained increase in Akt phosphorylation independently of phosphatidylinositol 3-kinase activation, which was essential for supporting T 3 -induced DC maturation and interleukin (IL)-12 production. This effect was dependent on intact TRβ 1 signaling as small interfering RNA-mediated silencing of TRβ 1 expression prevented T 3 -induced DC maturation and IL-12 secretion as well as Akt activation and IκB-ε degradation. In turn, T 3 up-regulated TRβ 1 expression through mechanisms involving NF-κB, suggesting an autocrine regulatory loop to control hormone-dependent TRβ 1 signaling. These findings were confirmed by chromatin immunoprecipitation analysis, which disclosed a new functional NF-κB consensus site in the promoter region of the TRB1 gene. Thus, a T 3 -induced NF-κB-dependent mechanism controls TRβ 1 expression, which in turn signals DCs to promote maturation and function via an Akt-dependent but PI3K-independent pathway. These results underscore a novel unrecognized target that regulates DC maturation and function with critical implications in immunopathology at the crossroads of the immune-endocrine circuits. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

Descripción: Specific receptors for the different gp130 cytokines, as well as the cytokines themselves, are expressed in anterior pituitary cells, providing the basis for the regulation of hormone secretion and cell growth (Figure 2). During an inflammatory response, both IL-6 and LIF increase (15, 17). LPS stimulates intrapituitary IL-6 production in FS cells via specific Toll receptors using the p38 MAPK-NF-κB pathway (20). Anti-IL-6 antibodies block the ACTH response of rat anterior pituitary cell cultures to LPS, showing the involvement of locally produced IL-6 (U. Renner et al., unpublished observations). Thus, during acute or chronic inflammation or infection, systemic, hypothalamic, or hypophyseal gp 130 cytokines may act on anterior pituitary cells, integrating the neuroendocrine response. The action of gp130 cytokines through the STAT3 transcription factor represents a powerful mechanism for regulation of pituitary corticotroph function. In response to different stressful stimuli, CRH stimulates the corticotrophs through cAMP/protein kinase A-mediated and calcium-mediated pathways and AP-1, CREB, and Nurr transcription factors. Cytokines may act on corticotrophs through different mechanisms; whereas IL-1 acts through Nur77, gp130 employs STAT3 for transcriptional activation. Cooperation between STAT3 and other transcription factors, such as NF-κB, AP-1, or the glucocorticoid receptor, has been described in other tissues (6), but it remains to be established whether this occurs in the pituitary. Future research clarifying the molecular mechanisms of gp130 action on pituitary cells will provide new clues regarding their involvement in neuro-endocrine responses to immune stimulation and will be of great importance for understanding pituitary pathophysiology.

Descripción: RSUME (RWD-containing SUMO Enhancer) is a small protein that increases SUMO conjugation to proteins. To date, four splice variants that codify three RSUME isoforms have been described, which differ in their C-terminal end. Comparing the structure of the RSUME isoforms we found that, in addition to the previously described RWD domain in the N-terminal, all these RSUME variants also contain an intermediate domain. Only the longest RSUME isoform presents a C-terminal domain that is absent in the others. Given these differences, we used the shortest and longest RSUME variants for comparative studies. We found that the C-terminal domain is dispensable for the SUMO-conjugation enhancer properties of RSUME. We also demonstrate that these two RSUME variants are equally induced by hypoxia. The NF-κB signaling pathway is inhibited and the HIF-1 pathway is increased more efficiently by the longest RSUME, by means of a greater physical interaction of RSUME267 with the target proteins. In addition, the mRNA and protein levels of these isoforms differ in human glioma samples; while the shortest RSUME isoform is expressed in all the tumors analyzed, the longest variant is expressed in most but not all of them. The results presented here show a degree of redundancy of the RSUME variants on the SUMO pathway. However, the increased inhibition conferred by RSUME267 over the NF-κB signaling pathway, the increased activation over the HIF-1 pathway and the different expression of the RSUME isoforms suggest specific roles for each RSUME isoform which may be relevant in certain types of brain tumors that express RSUME, like human pituitary adenomas and gliomas. © 2013 Gerez et al.

Descripción: The three related 160-kDa proteins, SRC-1, TIF-2 and RAC-3, were initially identified as factors interacting with nuclear receptors. They have also been reported to potentiate the activity of other transcription factors such as AP-1 or NF-κB. The aim of this work was to identify whether SRC-1 interferes with the TGF-β/Smad signaling pathway, and if so, to identify its underlying mechanisms of action. Using transient cell transfection experiments performed in human dermal fibroblasts with the Smad3/4-specific (SBE) 4-lux reporter construct, as well as the human PAI-1 promoter, we determined that SRC-1 enhances TGF-β-induced, Smad-mediated, transcription. Likewise, SRC-1 overexpression potentiated TGF-β-induced upregulation of PAI-1 steady-state mRNA levels. Using a mammalian two-hybrid system, we demonstrated that SRC-1 interacts with the transcriptional co-activators p300/CBP, but not with Smad3. Overexpression of the adenovirus E1A oncoprotein, an inhibitor of CBP/p300 activity, prevented the enhancing effect of SRC-1 on Smad3/4-mediated transcription, indicating that p300/CBP may be required for SRC-1 effect. Such hypothesis was validated, as expression of a mutant form of SRC-1 lacking the CBP/p300-binding site failed to upregulate Smad3/4-dependent transcription, while full-length SRC-1 potentiated p300-Smad3 interactions. These results identify SRC-1 as a novel Smad3/4 transcriptional partner, facilitating the functional link between Smad3 and p300/CBP. © 2005 Nature Publishing Group All rights reserved.