Response regulators are proteins that undergo transient phosphorylation, connecting specific signals to adaptive responses. Remarkably, the molecular mechanism of response regulator activation ...remains elusive, largely because of the scarcity of structural data on multidomain response regulators and histidine kinase/response regulator complexes. We now address this question by using a combination of crystallographic data and functional analyses in vitro and in vivo, studying DesR and its cognate sensor kinase DesK, a two-component system that controls membrane fluidity in Bacillus subtilis. We establish that phosphorylation of the receiver domain of DesR is allosterically coupled to two distinct exposed surfaces of the protein, controlling noncanonical dimerization/tetramerization, cooperative activation, and DesK binding. One of these surfaces is critical for both homodimerization- and kinase-triggered allosteric activations. Moreover, DesK induces a phosphorylation-independent activation of DesR in vivo, uncovering a novel and stringent level of specificity among kinases and regulators. Our results support a model that helps to explain how response regulators restrict phosphorylation by small-molecule phosphoryl donors, as well as cross talk with noncognate sensors.
The ability to sense and respond to environmental variations is an essential property for cell survival. Two-component systems mediate key signaling pathways that allow bacteria to integrate extra- or intracellular signals. Here we focus on the DesK/DesR system, which acts as a molecular thermometer in B. subtilis, regulating the cell membrane's fluidity. Using a combination of complementary approaches, including determination of the crystal structures of active and inactive forms of the response regulator DesR, we unveil novel molecular mechanisms of DesR's activation switch. In particular, we show that the association of the cognate histidine kinase DesK triggers DesR activation beyond the transfer of the phosphoryl group. On the basis of sequence and structural analyses of other two-component systems, this activation mechanism appears to be used in a wide range of sensory systems, contributing a further level of specificity control among different signaling pathways.
It has been postulated that monitoring measurable residual disease (MRD) could be used as a surrogate marker of progression-free survival (PFS) in chronic lymphocytic leukemia (CLL) patients after ...treatment with immunochemotherapy regimens. In this study, we analyzed the outcome of 84 patients at 3 years of follow-up after first-line treatment with fludarabine, cyclophosphamide and rituximab (FCR) induction followed by 36 months of rituximab maintenance thearpy. MRD was assessed by a quantitative four-color flow cytometry panel with a sensitivity level of 10
Eighty out of 84 evaluable patients (95.2%) achieved at least a partial response or better at the end of induction. After clinical evaluation, 74 patients went into rituximab maintenance and the primary endpoint was assessed in the final analysis at 3 years of follow-up. Bone marrow (BM) MRD analysis was performed after the last planned induction course and every 6 months in cases with detectable residual disease during the 36 months of maintenance therapy. Thirty-seven patients (44%) did not have detectable residual disease in the BM prior to maintenance therapy. Interestingly, 29 patients with detectable residual disease in the BM after induction no longer had detectable disease in the BM following maintenance therapy. After a median followup of 6.30 years, the median overall survival (OS) and PFS had not been reached in patients with either undetectable or detectable residual disease in the BM, who had achieved a complete response at the time of starting maintenance therapy. Interestingly, univariate analysis showed that after rituximab maintenance OS was not affected by IGHV status (mutated
unmutated OS: 85.7% alive at 7.2 years
79.6% alive at 7.3 years, respectively). As per protocol, 15 patients (17.8%), who achieved a complete response and undetectable peripheral blood and BM residual disease after four courses of induction, were allowed to stop fludarabine and cyclophosphamide and complete two additional courses of rituximab and continue with maintenance therapy for 18 cycles. Surprisingly, the outcome in this population was similar to that observed in patients who received the full six cycles of the induction regimen. These data show that, compared to historic controls, patients treated with FCR followed by rituximab maintenance have high-quality responses with fewer relapses and improved OS. The tolerability of this regime is favorable. Furthermore, attaining an early undetectable residual disease status could shorten the duration of chemoimmunotherapy, reducing toxicities and preventing long-term side effects. The analysis of BM MRD after fludarabine-based induction could be a powerful predictor of post-maintenance outcomes in patients with CLL undergoing rituximab maintenance and could be a valuable tool to identify patients at high risk of relapse, influencing further treatment strategies. This trial is registered with EudraCT n. 2007-002733-36 and ClinicalTrials.gov Identifier: NCT00545714.
All living organisms include a set of signaling devices that confer the ability to dynamically perceive and adapt to the fluctuating environment. Two-component systems are part of this sensory ...machinery that regulates the execution of different genetic and/or biochemical programs in response to specific physical or chemical signals. In the last two decades, there has been tremendous progress in our molecular understanding on how signals are detected, the allosteric mechanisms that control intramolecular information transmission and the specificity determinants that guarantee correct wiring. All this information is starting to be exploited in the development of new synthetic networks. Connecting multiple molecular players, analogous to programming lines of code, can provide the resources to build new sophisticated biocomputing systems. The Synthetic Biology field is starting to revolutionize several scientific fields, such as biomedicine and agriculture, propelling the development of new solutions. Expanding the spectrum of available nanodevices in the toolbox is key to unleash its full potential. This review aims to discuss, from a structural perspective, how to take advantage of the vast array of sensor and effector protein modules involved in two-component systems for the construction of new synthetic circuits.
Erlotinib and gefitinib are both tyrosine kinase inhibitors (TKIs) approved for the treatment of non-small cell lung cancer (NSCLC). Although it is well known that the increase of gastric pH may ...decrease the solubility of TKIs, there is limited evidence about the clinical repercussion of this fact. The purpose of this study was to determine if the use of gastric acid suppressive therapy (As) concomitantly with TKIs has an adverse impact on progression-free survival (PFS) and to determine whether the type of drug used (proton pump inhibitors/PPIs or histamine-2 receptors antagonists (H2RAs) may influence it.
In this retrospective observational study included were patients treated for ≥1 week with erlotinib or gefitinib from January 2012 to December 2015. Demographic, diagnostic and therapeutic variables were collected. Patients were divided into two groups (As users and non-As users). For the calculation of the PFS the Kaplan Meier and multivariate Cox regression analysis were used.
163 patients with mean age 70 years were included. 72.397percnt; (n=118) received TKIs and As concomitantly. The mean PFS was 84 days (95% CI, 65-101) and 221 days (95% CI, 125-429; p <0.0001) in As users and non-As users, respectively. Regarding the type of As used, no significant differences were observed.
Concomitant use of As and TKIs adversely impacted the PFS outcomes in NSCLC patients regardless of the type of As used. Further studies are needed to determine the clinical impact of interactions between antiacids and antineoplastics.
Phosphorylation carries chemical information in biological systems. In two-component systems (TCSs), the sensor histidine kinase and the response regulator are connected through phosphoryl transfer ...reactions that may be uni- or bidirectional. Directionality enables the construction of complex regulatory networks that optimize signal propagation and ensure the forward flow of information. We combined x-ray crystallography, hybrid quantum mechanics/molecular mechanics (QM/MM) simulations, and systems-integrative kinetic modeling approaches to study phosphoryl flow through the
thermosensing TCS DesK-DesR. The allosteric regulation of the histidine kinase DesK was critical to avoid back transfer of phosphoryl groups and futile phosphorylation-dephosphorylation cycles by isolating phosphatase, autokinase, and phosphotransferase activities. Interactions between the kinase's ATP-binding domain and the regulator's receiver domain placed the regulator in two distinct positions in the phosphotransferase and phosphatase complexes, thereby determining whether a key glutamine residue in DesK was properly situated to assist in the dephosphorylation reaction. Moreover, an energetically unfavorable phosphotransferase conformation when DesK was not phosphorylated minimized reverse phosphoryl transfer. DesR dimerization and a dissociative phosphoryl transfer reaction also enforced the direction of phosphoryl flow. Shorter or longer distances between the phosphoryl acceptor and donor residues shifted the phosphoryl transfer equilibrium by modulating the stabilizing effect of the Mg
cofactor. These mechanisms control the directionality of signal transmission and show how structure-encoded allostery stores and transmits information in signaling systems.
•Phenazines 2c and 3a emerged as chemosensitizer agents to bladder cancer cells.•The HDAC inhibitory activity appears as one of the mechanism of action of 2c.•Phenazine dioxide 3a induced a ...sensitizer effect independent from HDAC inhibition.•Phenazine dioxides 2c and 3a presented low toxicity levels against normal cells.•Compounds 2c and 3a are good scaffolds for the further design of sensitizer agents.
We determined the chemosensitizer effect of phenazine dioxide derivatives to cisplatin and the possible mechanism of action on bladder cancer cells. Anti-proliferative activity of nine phenazine dioxide derivatives in presence or absence of cisplatin was evaluated in two bladder tumor human cells T24 and 253 J and one non tumor cell line V79-4.
The sensitizer effect of the combined treatment was determined by chromosomal aberrations and micronucleus test. A possible mechanism of action of the sensitizer compounds as HDACi was also investigated.The phenazine dioxide 2c combined with cisplatin induced a cell cycle arrest on bladder cancer cells and resensitize the invasive and cisplatin resistant 253 J cell line. The HDAC inhibitory activity appears as one of the mechanism of action of the compound. The low toxicity levels against normal cells point out the phenazine dioxide derivative 2c as a very good scaffold for further design of HDACi sensitizer agents.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Se aportan conocimientos sobre la distribución de briófitos del Herbario MACB incluidos en la lista de especies amenazadas o raras de la Península Ibérica (España).
We have identified phenazine 5,10-dioxides as prodrugs for antitumour therapy that undergo hypoxic-selective bioreduction to form cytotoxic species. Here, we investigated some structural ...modifications in order to find new selective hypoxic cytotoxins and to establish the structural requirements for adequate activity. Three different chemical-series were prepared and the clonogenic survival of V79 cells on aerobic and anaerobic conditions was determined. Electrochemical- and DNA-interaction studies were done for the most relevant derivatives. The new fluoro-derivative 7-fluoro-2-aminophenazine 5,10-dioxide displayed selective toxicity towards hypoxic V79 cells having adequate hypoxic cytotoxicity ratio (HCR
=
6.8) and being the most potent hypoxic cytotoxins (
P
=
2.5
μM) described for this family of bioreductive agents. The reduction potential of the
N-oxide moiety in this new fluoro-derivative was in the range for adequate bioreduction property. According to the fluorescence studies, the DNA-interaction mechanism was especially operative in the phenazine drugs more than in the corresponding prodrugs, phenazine dioxides.
Display omitted 7-Fluoro-2-aminophenazine 5,10-dioxide was identified as new bioreductive agent (HCR
=
6.8,
P
hypoxia
=
2.5
μM).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK