bims-nenemi 2023-06-04 papers

Issue of 2023–06–04
three papers selected by
Marco Tigano, Thomas Jefferson University

Sci Adv. 2023 Jun 02. 9(22): eadg7940

Creation of distinctive Bax-lipid complexes at mitochondrial membrane surfaces drives pore formation to initiate apoptosis.

Luke A Clifton, Hanna P Wacklin-Knecht, Jörgen Ådén, Ameeq Ul Mushtaq, Tobias Sparrman, Gerhard Gröbner.

Apotosis is an essential process tightly regulated by the Bcl-2 protein family where proapoptotic Bax triggers cell death by perforating the mitochondrial outer membrane. Although intensively studied, the molecular mechanism by which these proteins create apoptotic pores remains elusive. Here, we show that Bax creates pores by extracting lipids from outer mitochondrial membrane mimics by formation of Bax/lipid clusters that are deposited on the membrane surface. Time-resolved neutron reflectometry and Fourier transform infrared spectroscopy revealed two kinetically distinct phases in the pore formation process, both of which were critically dependent on cardiolipin levels. The initially fast adsorption of Bax on the mitochondrial membrane surface is followed by a slower formation of pores and Bax-lipid clusters on the membrane surface. Our findings provide a robust molecular understanding of mitochondrial membrane perforation by cell-killing Bax protein and illuminate the initial phases of programmed cellular death.

DOI: https://doi.org/10.1126/sciadv.adg7940

Commun Biol. 2023 May 30. 6(1): 578

Differential Binding of NLRP3 to non-oxidized and Ox-mtDNA mediates NLRP3 Inflammasome Activation.

Angela Cabral, Julia Elise Cabral, Angelina Wang, Yiyang Zhang, Hailin Liang, Donya Nikbakht, Leslie Corona, Hal M Hoffman, Reginald McNulty.

The NLRP3 inflammasome is a key mediator of the innate immune response to sterile tissue injury and is involved in many chronic and acute diseases. Physically and chemically diverse agents activate the NLRP3 inflammasome. Here, we show that NLRP3 binds non-oxidized and Ox-mtDNA differentially, with a half maximum inhibitory concentration (IC50) for non-oxidized and Ox-mtDNA of 4 nM and 247.2 nM, respectively. The NLRP3 Neonatal-Onset Multisystem Inflammatory Disease (NOMIDFCAS) gain of function mutant could bind non-oxidized mtDNA but had higher affinity for Ox-mtDNA compared to WT with an IC50 of 8.1 nM. NLRP3 lacking the pyrin domain can bind both oxidized and non-oxidized mtDNA. Isolated pyrin domain prefers Ox-mtDNA. The NLRP3 pyrin domain shares a protein fold with DNA glycosylases and generate a model for DNA binding based on the structure and sequence alignment to Clostridium acetobutylicum and human OGG1, an inhibitor of Ox-mtDNA generation, 8-oxoguanine DNA glycosylases. We provide a new model for how NLRP3 interacts with Ox-mtDNA supported by DNA binding in the presence of a monoclonal antibody against the pyrin domain. These results give new insights into the mechanism of inflammasome assembly, and into the function of reactive oxygen species in establishing a robust immune response.

DOI: https://doi.org/10.1038/s42003-023-04817-y

iScience. 2023 Jun 16. 26(6): 106872

Inflammation conditional genome editing mediated by the CRISPR-Cas9 system.

Tingting Yuan, Honglin Tang, Xiaojie Xu, Jingjing Shao, Gaojun Wu, Young-Chang Cho, Yuan Ping, Guang Liang.

The specificity of CRISPR-Cas9 in response to particular pathological stimuli remains largely unexplored. Hence, we designed an inflammation-inducible CRISPR-Cas9 system by grafting a sequence that binds with NF-κB to the CRISPR-Cas9 framework, termed NBS-CRISPR. The genetic scissor function of this developed genome-editing tool is activated on encountering an inflammatory attack and is inactivated or minimized in non-inflammation conditions. Furthermore, we employed this platform to reverse inflammatory conditions by targeting the MyD88 gene, a crucial player in the NF-κB signaling pathway, and achieved impressive therapeutic effects. Finally, during inflammation, P65 (RELA) can translocate to the nucleus from the cytoplasm. Herein, to avoid Cas9 leaky DNA cleavage activity i, we constructed an NBS-P65-CRISPR system expressing the Cas9-p65 fusion protein. Our inflammation inducible Cas9-mediated genome editing strategy provides new perspectives and avenues for pathological gene interrogation.

Keywords: Biotechnology; Components of the immune system; Immune response

DOI: https://doi.org/10.1016/j.isci.2023.106872