RESUMO
Pathogen infection of host cells triggers an inflammatory cell death termed pyroptosis via activation of inflammatory caspases. However, blockade of immune signaling kinases by the Yersinia virulence factor YopJ triggers cell death involving both apoptotic caspase-8 and pyroptotic caspase-1. While caspase-1 is normally activated within inflammasomes, Yersinia-induced caspase-1 activation is independent of known inflammasome components. We report that caspase-8 is an essential initiator, while caspase-1 is an essential amplifier of its own activation through two feed-forward loops involving caspase-1 auto-processing and caspase-1-dependent activation of gasdermin D and NLPR3. Notably, while Yersinia-induced caspase-1 activation and cell death are inflammasome-independent, IL-1ß release requires NLPR3 inflammasome activation. Mechanistically, caspase-8 is rapidly activated within multiple foci throughout the cell, followed by assembly of a canonical inflammasome speck, indicating that caspase-8 and canonical inflammasome complex assemblies are kinetically and spatially distinct. Our findings reveal that functionally interconnected but distinct death complexes mediate pyroptosis and IL-1ß release in response to pathogen blockade of immune signaling.
Assuntos
Caspase 1 , Caspase 8 , Inflamassomos , Interleucina-1beta , Proteínas de Ligação a Fosfato , Piroptose , Transdução de Sinais , Yersinia , Interleucina-1beta/metabolismo , Caspase 8/metabolismo , Animais , Caspase 1/metabolismo , Inflamassomos/metabolismo , Yersinia/metabolismo , Proteínas de Ligação a Fosfato/metabolismo , Camundongos , Humanos , Proteínas de Bactérias/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Yersiniose/imunologia , Yersiniose/microbiologia , Yersiniose/metabolismo , GasderminasRESUMO
While the zinc finger transcription factors EGR1, EGR2, and EGR3 are recognized as critical for T-cell function, the role of EGR4 remains unstudied. Here, we show that EGR4 is rapidly upregulated upon TCR engagement, serving as a critical "brake" on T-cell activation. Hence, TCR engagement of EGR4-/- T cells leads to enhanced Ca2+ responses, driving sustained NFAT activation and hyperproliferation. This causes profound increases in IFNγ production under resting and diverse polarizing conditions that could be reversed by pharmacological attenuation of Ca2+ entry. Finally, an in vivo melanoma lung colonization assay reveals enhanced anti-tumor immunity in EGR4-/- mice, attributable to Th1 bias, Treg loss, and increased CTL generation in the tumor microenvironment. Overall, these observations reveal for the first time that EGR4 is a key regulator of T-cell differentiation and function.
Assuntos
Sinalização do Cálcio , Fatores de Transcrição de Resposta de Crescimento Precoce , Neoplasias , Animais , Diferenciação Celular , Ativação Linfocitária , Camundongos , Microambiente Tumoral , Dedos de ZincoRESUMO
Ca2+ signals, which facilitate pluripotent changes in cell fate, reflect the balance between cation entry and export. We found that overexpression of either isoform of the Ca2+-extruding plasma membrane calcium ATPase 4 (PMCA4) pump in Jurkat T cells unexpectedly increased activation of the Ca2+-dependent transcription factor nuclear factor of activated T cells (NFAT). Coexpression of the endoplasmic reticulum-resident Ca2+ sensor stromal interaction molecule 1 (STIM1) with the PMCA4b splice variant further enhanced NFAT activity; however, coexpression with PMCA4a depressed NFAT. No PMCA4 splice variant dependence in STIM1 association was observed, whereas partner of STIM1 (POST) preferentially associated with PMCA4b over PMCA4a, which enhanced, rather than inhibited, PMCA4 function. A comparison of global and near-membrane cytosolic Ca2+ abundances during store-operated Ca2+ entry revealed that PMCA4 markedly depressed near-membrane Ca2+ concentrations, particularly when PMCA4b was coexpressed with STIM1. PMCA4b closely associated with both POST and the store-operated Ca2+ channel Orai1. Furthermore, POST knockdown increased the near-membrane Ca2+ concentration, inhibiting the global cytosolic Ca2+ increase. These observations reveal an unexpected role for POST in coupling PMCA4 to Orai1 to promote Ca2+ entry during T cell activation through Ca2+ disinhibition.
Assuntos
Sinalização do Cálcio , Cálcio/metabolismo , Membrana Celular/metabolismo , Fatores de Transcrição NFATC/metabolismo , ATPases Transportadoras de Cálcio da Membrana Plasmática/metabolismo , Retículo Endoplasmático/metabolismo , Células HEK293 , Humanos , Células Jurkat , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Microscopia de Fluorescência , Proteína ORAI1/genética , Proteína ORAI1/metabolismo , ATPases Transportadoras de Cálcio da Membrana Plasmática/genética , Interferência de RNA , Molécula 1 de Interação Estromal/genética , Molécula 1 de Interação Estromal/metabolismoRESUMO
Ca2+ is a ubiquitous, dynamic and pluripotent second messenger with highly context-dependent roles in complex cellular processes such as differentiation, proliferation, and cell death. These Ca2+ signals are generated by Ca2+-permeable channels located on the plasma membrane (PM) and endoplasmic reticulum (ER) and shaped by PM- and ER-localized pumps and transporters. Differences in the expression of these Ca2+ homeostasis proteins contribute to cell and context-dependent differences in the spatiotemporal organization of Ca2+ signals and, ultimately, cell fate. This review focuses on the Early Growth Response (EGR) family of zinc finger transcription factors and their role in the transcriptional regulation of Stromal Interaction Molecule (STIM1), a critical regulator of Ca2+ entry in both excitable and non-excitable cells.
Assuntos
Sinalização do Cálcio , Cálcio/metabolismo , Membrana Celular/metabolismo , Fatores de Transcrição de Resposta de Crescimento Precoce/metabolismo , Retículo Endoplasmático/metabolismo , Regulação da Expressão Gênica , Proteínas de Neoplasias/biossíntese , Molécula 1 de Interação Estromal/biossíntese , Animais , HumanosRESUMO
In a September 2018 paper published in Nature Communications, Gong et al. identified the domains through which human PMCA1 and neuroplastin (NPTN) interact. Upon binding, hPMCA1 TM domains separate T110 in TM1 and A370 in TM3 to reveal the Ca2+-binding site. Thus, NPTN is able to directly modulate the accessibility of cytosolic Ca2+ to PMCA.