Tuning MPL signaling to influence hematopoietic stem cell differentiation and inhibit essential thrombocythemia progenitors
Proceedings of the National Academy of Sciences
2021; 118 (2) (Jan 2021)
View details for DOI 10.1073/pnas.2017849118
The heme-regulated inhibitor is a cytosolic sensor of protein misfolding that controls innate immune signaling
2019; 365 (6448): 47-+
Multiple cytosolic innate sensors form large signalosomes after activation, but this assembly needs to be tightly regulated to avoid accumulation of misfolded aggregates. We found that the eIF2α kinase heme-regulated inhibitor (HRI) controls NOD1 signalosome folding and activation through a process requiring eukaryotic initiation factor 2α (eIF2α), the transcription factor ATF4, and the heat shock protein HSPB8. The HRI/eIF2α signaling axis was also essential for signaling downstream of the innate immune mediators NOD2, MAVS, and TRIF but dispensable for pathways dependent on MyD88 or STING. Moreover, filament-forming α-synuclein activated HRI-dependent responses, which suggests that the HRI pathway may restrict toxic oligomer formation. We propose that HRI, eIF2α, and HSPB8 define a novel cytosolic unfolded protein response (cUPR) essential for optimal innate immune signaling by large molecular platforms, functionally homologous to the PERK/eIF2α/HSPA5 axis of the endoplasmic reticulum UPR.
View details for DOI 10.1126/science.aaw4144
View details for Web of Science ID 000474432700029
View details for PubMedID 31273097
Shiga Toxin/Lipopolysaccharide Activates Caspase-4 and Gasdermin D to Trigger Mitochondrial Reactive Oxygen Species Upstream of the NLRP3 Inflammasome
2018; 25 (6): 1525–U20
The non-canonical caspase-4 and canonical NLRP3 inflammasomes are both activated by intracellular lipopolysaccharide (LPS), but the crosstalk between these two pathways remains unclear. Shiga toxin 2 (Stx2)/LPS complex, from pathogenic enterohemorrhagic Escherichia coli, activates caspase-4, gasdermin D (GSDMD), and the NLRP3 inflammasome in human THP-1 macrophages, but not mouse macrophages that lack the Stx receptor CD77. Stx2/LPS-mediated IL-1β secretion and pyroptosis are dependent on mitochondrial reactive oxygen species (ROS) downstream of the non-canonical caspase-4 inflammasome and cleaved GSDMD, which is enriched at the mitochondria. Blockade of caspase-4 activation and ROS generation as well as GSDMD deficiency significantly reduces Stx2/LPS-induced IL-1β production and pyroptosis. The NLRP3 inflammasome plays a significant role in amplifying Stx2/LPS-induced GSDMD cleavage and pyroptosis, with significant reduction of these responses in NLRP3-deficient THP-1 cells. Together, these data show that Stx2/LPS complex activates the non-canonical inflammasome and mitochondrial ROS upstream of the NLRP3 inflammasome to promote cytokine maturation and pyroptosis.
View details for DOI 10.1016/j.celrep.2018.09.071
View details for Web of Science ID 000455666100001
View details for PubMedID 30404007
Tracing the origins of relapse in acute myeloid leukaemia to stem cells
2017; 547 (7661): 104-+
In acute myeloid leukaemia, long-term survival is poor as most patients relapse despite achieving remission. Historically, the failure of therapy has been thought to be due to mutations that produce drug resistance, possibly arising as a consequence of the mutagenic properties of chemotherapy drugs. However, other lines of evidence have pointed to the pre-existence of drug-resistant cells. For example, deep sequencing of paired diagnosis and relapse acute myeloid leukaemia samples has provided direct evidence that relapse in some cases is generated from minor genetic subclones present at diagnosis that survive chemotherapy, suggesting that resistant cells are generated by evolutionary processes before treatment and are selected by therapy. Nevertheless, the mechanisms of therapy failure and capacity for leukaemic regeneration remain obscure, as sequence analysis alone does not provide insight into the cell types that are fated to drive relapse. Although leukaemia stem cells have been linked to relapse owing to their dormancy and self-renewal properties, and leukaemia stem cell gene expression signatures are highly predictive of therapy failure, experimental studies have been primarily correlative and a role for leukaemia stem cells in acute myeloid leukaemia relapse has not been directly proved. Here, through combined genetic and functional analysis of purified subpopulations and xenografts from paired diagnosis/relapse samples, we identify therapy-resistant cells already present at diagnosis and two major patterns of relapse. In some cases, relapse originated from rare leukaemia stem cells with a haematopoietic stem/progenitor cell phenotype, while in other instances relapse developed from larger subclones of immunophenotypically committed leukaemia cells that retained strong stemness transcriptional signatures. The identification of distinct patterns of relapse should lead to improved methods for disease management and monitoring in acute myeloid leukaemia. Moreover, the shared functional and transcriptional stemness properties that underlie both cellular origins of relapse emphasize the importance of developing new therapeutic approaches that target stemness to prevent relapse.
View details for DOI 10.1038/nature22993
View details for Web of Science ID 000404839900039
View details for PubMedID 28658204
Ectopic miR-125a Expression Induces Long-Term Repopulating Stem Cell Capacity in Mouse and Human Hematopoietic Progenitors
CELL STEM CELL
2016; 19 (3): 383–96
Umbilical cord blood (CB) is a convenient and broadly used source of hematopoietic stem cells (HSCs) for allogeneic stem cell transplantation. However, limiting numbers of HSCs remain a major constraint for its clinical application. Although one feasible option would be to expand HSCs to improve therapeutic outcome, available protocols and the molecular mechanisms governing the self-renewal of HSCs are unclear. Here, we show that ectopic expression of a single microRNA (miRNA), miR-125a, in purified murine and human multipotent progenitors (MPPs) resulted in increased self-renewal and robust long-term multi-lineage repopulation in transplanted recipient mice. Using quantitative proteomics and western blot analysis, we identified a restricted set of miR-125a targets involved in conferring long-term repopulating capacity to MPPs in humans and mice. Our findings offer the innovative potential to use MPPs with enhanced self-renewal activity to augment limited sources of HSCs to improve clinical protocols.
View details for DOI 10.1016/j.stem.2016.06.008
View details for Web of Science ID 000388991400015
View details for PubMedID 27424784
View details for PubMedCentralID PMC5500905
- miR-126 Regulates Distinct Self-Renewal Outcomes in Normal and Malignant Hematopoietic Stem Cells (vol 29, pg 214, 2016) CANCER CELL 2016; 29 (4): 602–6
Stat3 is a positive regulator of gap junctional intercellular communication in cultured, human lung carcinoma cells
2012; 12: 605
Neoplastic transformation of cultured cells by a number of oncogenes such as src suppresses gap junctional, intercellular communication (GJIC); however, the role of Src and its effector Signal transducer and activator of transcription-3 (Stat3) upon GJIC in non small cell lung cancer (NSCLC) has not been defined. Immunohistochemical analysis revealed high Src activity in NSCLC biopsy samples compared to normal tissues. Here we explored the potential effect of Src and Stat3 upon GJIC, by assessing the levels of tyr418-phosphorylated Src and tyr705-phosphorylated Stat3, respectively, in a panel of NSCLC cell lines.Gap junctional communication was examined by electroporating the fluorescent dye Lucifer yellow into cells grown on a transparent electrode, followed by observation of the migration of the dye to the adjacent, non-electroporated cells under fluorescence illumination.An inverse relationship between Src activity levels and GJIC was noted; in five lines with high Src activity GJIC was absent, while two lines with extensive GJIC (QU-DB and SK-LuCi6) had low Src levels, similar to a non-transformed, immortalised lung epithelial cell line. Interestingly, examination of the mechanism indicated that Stat3 inhibition in any of the NSCLC lines expressing high endogenous Src activity levels, or in cells where Src was exogenously transduced, did not restore GJIC. On the contrary, Stat3 downregulation in immortalised lung epithelial cells or in the NSCLC lines displaying extensive GJIC actually suppressed junctional permeability.Our findings demonstrate that although Stat3 is generally growth promoting and in an activated form it can act as an oncogene, it is actually required for gap junctional communication both in nontransformed lung epithelial cells and in certain lung cancer lines that retain extensive GJIC.
View details for DOI 10.1186/1471-2407-12-605
View details for Web of Science ID 000315026700001
View details for PubMedID 23244248
View details for PubMedCentralID PMC3575370
Mind the gap; regulation of gap junctional, intercellular communication by the SRC oncogene product and its effectors.
2012; 32 (10): 4245-50
Gap junctions are channels that connect the interiors of neighboring cells and are formed by the connexin (Cx) proteins. A reduction in gap junctional, intercellular communication (GJIC) often correlates with increased growth and neoplastic transformation. Cx43 is a widely expressed connexin which can be phosphorylated by the Src oncoprotein tyrosine kinase on tyr247 and -265, and this reduces communication. However, Src activates multiple signalling pathways such as the Ras/Raf/Erk and PLCγ/protein kinase C, which can also phosphorylate Cx43 and interrupt communication. In addition, the Src effector Cas, which has an adaptor function, binds Cx43 to suppress gap junctional communication. In sharp contrast, activation of a different Src effector, the cytoplasmic transcription factor Signal transducer and activator of transcription-3 (Stat3) is not required for the Src-mediated, GJIC suppression. In fact, Stat3 is actually required for the maintenance of gap junctional communication in normal cells with high GJIC.
View details for PubMedID 23060544