Project description:In this study, AC2P20 was prioritized for continued study to test the hypothesis that it was targeting Mtb pathways associated with pH-driven adaptation. RNAseq transcriptional profiling studies showed AC2P20 modulates expression of genes associated with redox-homeostasis. Gene enrichment analysis revealed that the AC2P20 transcriptional profile had significant overlap with a previously characterized pH-selective inhibitor, AC2P36. Like AC2P36, we show that AC2P20 kills Mtb by selectively depleting free thiols at acidic pH. Mass spectrometry studies show the formation of a disulfide bond between AC2P20 and reduced glutathione, supporting a mechanism where AC2P20 is able to deplete intracellular thiols and dysregulate redox homeostasis.
Project description:B cells differentiate into antibody-producing plasma cells, which are critical for humoral immunity, autoimmunity, and vaccine responses. Despite the importance of environmental stressors on regulating humoral immune responses, the influence of pH on PC differentiation has not been described. Here, we identified SLC4A7, a sodium/bicarbonate cotransporter, as a selective regulator of PC differentiation. SLC4A7 deletion impaired the formation of PCs and humoral immunity to influenza A virus infection in mice. Mechanistically, we find that SLC4A7 prevents acidification of intracellular pH and thus maintains lysosomal function and mTORC1 activity. Loss of SLC4A7 suppresses PC differentiation under conditions of extracellular acidosis in vitro and in a mouse model of metabolic acidosis. Here we reveal a novel relationship between the regulation of intracellular pH by SLC4A7 and mTORC1-dependent PC differentiation and humoral immunity.
Project description:The conditions of the tumor microenvironment, such as hypoxia and nutrient starvation, play critical roles in cancer progression. However, the role of acidic extracellular pH in cancer progression is not studied as extensively as that of hypoxia. Here, we show that extracellular acidic pH (pH 6.8) triggered activation of sterol regulatory element-binding protein 2 (SREBP2) by stimulating nuclear translocation and promoter binding to its targets along with intracellular acidification. Interestingly, inhibition of SREBP2, but not SREBP1, suppressed the upregulation of low pH-induced cholesterol biosynthesis-related genes. Moreover, acyl-CoA synthetase short-chain family member 2 (ACSS2), a direct SREBP2 target, provided a growth advantage to cancer cells under acidic pH. Furthermore, acidic pH-responsive SREBP2 target genes were associated with reduced overall survival of cancer patients. Thus, our findings show that SREBP2 is a key transcriptional regulator of metabolic genes and progression of cancer cells, partly in response to extracellular acidification.
Project description:Intracellular pH (pHi) dynamics regulates diverse cell processes such as proliferation, dysplasia, and differentiation, often mediated by the protonation state of a functionally critical histidine residue in endogenous pH sensing proteins. How pHi dynamics can directly regulate gene expression and whether transcription factors can function as pH sensors has received limited attention. We tested the prediction that transcription factors with a histidine in their DNA binding domain (DBD) that forms hydrogen bonds with nucleotides can have pH-regulated activity, which is relevant to more than 85 transcription factors in distinct families, including FOX, KLF, SOX and MITF/Myc. Focusing on FOX family transcription factors, we used unbiased SELEX-seq to identify pH-dependent DNA binding motif preferences, then confirm pH-regulated binding affinities for FOXC2, FOXM1, and FOXN1 to a canonical FkhP DNA motif that are 2.5 to 7.5 greater at pH 7.0 compared with pH 7.5. For FOXC2, we also find greater activity for an FkhP motif at lower pHi in cells and that pH-regulated binding and activity are dependent on a conserved histidine (His122) in the DBD. RNA-seq with FOXC2 also reveals pH-dependent differences in enriched promoter motifs. Our findings identify pH-regulated transcription factor-DNA binding selectivity with relevance to how pHi dynamics can regulate gene expression for myriad cell behaviours.
Project description:The paper describes a model of pH control in tumor.
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This model is described in the article:
Regulation of tumour intracellular pH: A mathematical model examining the interplay between H and lactate
Maymona Al-Husari, Steven D. Webb
Journal of Theoretical Biology 322 (2013) 58–71
Abstract:
Non-invasive measurements of pH have shown that both tumour and normal cells have intracellular pH (pHi) that lies on the alkaline side of neutrality (7.1–7.2). However, extracellular pH (pHe) is reported to be more acidic in some tumours compared to normal tissues. Many cellular processes and therapeutic agents are known to be tightly pH dependent which makes the study of intracellular pH regulation of paramount importance. We develop a mathematical model that examines the role of various membrane-based ion transporters in tumour pH regulation, in particular, with a focus on the interplay between lactate and H ions and whether the lactate/H symporter activity is sufficient to give rise to the observed reversed pH gradient that is seen is some tumours. Using linear stability analysis and H ions. We extend this analysis using perturbation techniques to specifically examine a rapid change in H-ion concentrations relative to variations in lactate. We then perform a parameter sensitivity analysis to explore solution robustness to parameter variations. An important result from our study is that a reversed pH gradient is possible in our system but for unrealistic parameter estimates—pointing to the possible involvement of other mechanisms in cellular pH gradient reversal, for example acidic vesicles, lysosomes, golgi and endosomes.
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Project description:Intracellular pH (pHi) dynamics regulates diverse cell processes such as proliferation, dysplasia, and differentiation, often mediated by the protonation state of a functionally critical histidine residue in endogenous pH sensing proteins. How pHi dynamics can directly regulate gene expression and whether transcription factors can function as pH sensors has received limited attention. We tested the prediction that transcription factors with a histidine in their DNA binding domain (DBD) that forms hydrogen bonds with nucleotides can have pH-regulated activity, which is relevant to more than 85 transcription factors in distinct families, including FOX, KLF, SOX and MITF/Myc. Focusing on FOX family transcription factors, we used unbiased SELEX-seq to identify pH-dependent DNA binding motif preferences, then confirm pH-regulated binding affinities for FOXC2, FOXM1, and FOXN1 to a canonical FkhP DNA motif that are 2.5 to 7.5 greater at pH 7.0 compared with pH 7.5. For FOXC2, we also find greater activity for an FkhP motif at lower pHi in cells and that pH-regulated binding and activity are dependent on a conserved histidine (His122) in the DBD. RNA-seq with FOXC2 also reveals pH-dependent differences in enriched promoter motifs. Our findings identify pH-regulated transcription factor-DNA binding selectivity with relevance to how pHi dynamics can regulate gene expression for myriad cell behaviours.
Project description:We aim to compare the genomic discrepancies across de novo Ph+ ALL, Ph+ MPAL and Ph+ AML, three diseases characterized by the occurrence of BCR-ABL1 transcripts but showing varied immunophenotypes. The data we are now submitting is the genomic copy number variants of these three groups. The following is the abstract with associated manuscript. The chromosome abnormality of Philadelphia (Ph) is typically seen in de novo acute lymphoblastic leukemia (ALL). It has also been identified in mixed phenotype acute leukemia (MPAL) and acute myeloid leukemia (AML) in the revisions to World Health Organization classification of myeloid neoplasms and actue leukemia. The discrepancies between these patients and potential mechanisms underlying differentiation fate of the leukemia cells remain poorly defined. We evaluated the clinical, genomic and transcriptomic features of Ph+ ALL, Ph+ MPAL and Ph+ AML by taking advantage of high-density genomic analysis, including next-generation sequencing array comparative genomic hybridization and gene expression profiling for transcriptomic analysis. Our results showed that the three cohorts demonstrated diversified clinical features. Ph+ ALL had the best response to induction therapy, with a complete remission (CR) rate of 93.5 and molecular response of 43.5%. Ph+ MPAL had a 90.0% CR rate but only 5.9% of molecular response. The CR rate of Ph+ AML was only 68.8%. Ph+ ALL was characterized by loss and mutations of B-cell development gene IKZF1 and PAX5, and frequent histone H3K36 trimethyltransferase SETD2 mutations. SETD2 mutations were detected in 11.3% of Ph+ ALL patients and predicted higher relapse rate. Ph+ MPAL and Ph+ AML featured high frequency of RUNX1 mutations. Further studies showed RUNX1-R177X mutation inhibited 32D cell differentiation induced by G-Csf, and cooperated with BCR-ABL1 to lead to myeloid differentiation arrest of human cord blood CD34+ cells. It is therefore presumed that these additional mutations work in synergy with BCR-ABL1 fusion gene to facilitate the development of Ph-positive acute leukemia in different immunophenotypic classifications.