bims-mecosi 2023-01-15 papers

Issue of 2023–01–15
three papers selected by
Verena Kohler, University of Graz

Front Cell Dev Biol. 2022 ;10 1074443

Endoplasmic reticulum-Phagosome contact sites from the cradle to the grave.

Phagocytosis is a key component of the innate immune system used to ingest apoptotic cells and microorganisms for their destruction and recycling of macromolecules and the presentation of antigens to adaptive immune system cells. The newly formed vacuole or nascent phagosome undergoes a maturation process reminiscent of the classical endocytic maturation process, reaching a highly degradative phagolysosome stage before its tubulovesicular breakdown into lysosomes. The process is highly regulated and can be disrupted by various pathogenic organisms. The exchange of proteins, lipids, and other metabolites between organelles, including maturing phagosomes, is enabled by two processes, vesicular and non-vesicular transport at membrane contact sites (MCS). For decades the specific role(s) of the endoplasmic reticulum (ER) in phagocytosis has been the subject of much debate. In parallel, the last two decades have seen a burst in research on the numerous roles of ER contact sites and resident proteins in all aspects of organelle biology. Here, in this minireview, we describe ER-phagosome contact sites' functions from the early stages of particle engulfment to the phagolysosome dissolution into lysosomes. We also discuss several aspects of ER-phagosome contact sites that remain to be explored.

Keywords: ER contact sites; ORP1L; STIM-ORAI; calcium; cholesterol; phagocytosis; phagolysosome; phagosome

DOI: https://doi.org/10.3389/fcell.2022.1074443

J Biochem Mol Toxicol. 2023 Jan 13. e23303

Mitochondria-associated endoplasmic reticulum membranes dysfunction contributes to PARP-1-dependent cell death under oxidative stress in retinal precursor cells.

Yuting Yang, Jihong Wu, Wei Lu, Yiqin Dai, Youjia Zhang, Xinghuai Sun.

Persistent poly (ADP-ribose) polymerase 1 (PARP-1) activation has proven detrimental and can lead to PARP-1-dependent cell death. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) serve as essential hubs for many biological pathways, such as autophagy and mitochondria fission and fusion. This study aimed to alleviate the effects of hydrogen peroxide (H2 O2 )-induced persistent PARP-1 activation and MAM dysregulation by the usage of a PARP-1 inhibitor. Results showed that receptor-interacting protein kinase (RIPK) 1 inhibitor (necrostatin-1) and PARP-1 inhibitor (olaparib) protected retinal precursor cells from H2 O2 -induced death, while a pan-caspase inhibitor (Z-VAD-FMK) failed to protect R28 cells. Olaparib also alleviated H2 O2 -induced MAM dysregulation, as evidenced by decreased VDAC1/ITPR3 interactions and reduced mitochondrial membrane potential collapse. Additionally, olaparib also inhibited H2 O2 -induced autophagy. Inhibiting autophagic flux increased MAM signaling under both normal and oxidative conditions. Furthermore, H2 O2 treatment caused a reduction in the protein level of mitofusin-2 (MFN2) in a dose- and time-dependent manner. Mfn2 knockdown was found to further magnify MAM dysregulation and mitochondrial dysfunction under normal and oxidative conditions. Mfn2 overexpression surprisingly enhanced H2 O2 -induced MAM signaling and failed to rescue H2 O2 -induced mitochondrial dysfunction. These results indicate that MAMs probably serve as a membrane source for oxidative stress-associated autophagy. MAM dysregulation also contributed to H2 O2 -induced PARP-1-dependent cell death. However, more studies are required to decipher the link between the modulation of Mfn2 expression, changes in MAM integrity, and alterations in mitochondrial performances.

Keywords: MAM; MFN2; Olaparib; PARP-1; hydrogen peroxide

DOI: https://doi.org/10.1002/jbt.23303

ACS Appl Mater Interfaces. 2023 Jan 11.

Inter-Organelle Contact Sites Mediate the Intracellular Antioxidant Activity of Platinum Nanozymes: A New Perspective on Cell-Nanoparticle Interaction and Signaling.

Vincenzo Migliaccio, Naym Blal, Micaela De Girolamo, Valentina Mastronardi, Federico Catalano, Ilaria Di Gregorio, Lillà Lionetti, Pier Paolo Pompa, Daniela Guarnieri.

The catalytic and antioxidant properties of platinum nanoparticles (PtNPs) make them promising candidates for several applications in nanomedicine. However, an open issue, still shared among most nanomaterials, is the understanding on how internalized PtNPs, which are confined within endo-lysosomal compartments, can exert their activities. To address this problem, here we study the protective effect of 5 nm PtNPs on a human hepatic (HepG2) cell line exposed to dichlorodiphenylethylene (DDE) as a model of oxidative stress. Our results indicate that PtNPs are very efficient to reduce DDE-induced damage in HepG2 cells, in an extent that depends on DDE dose. PtNPs can contrast the unbalance of mitochondrial dynamics induced by DDE and increase the expression of the SOD2 mitochondrial enzyme that recovers cells from oxidative stress. Interestingly, in cells treated with PtNPs─alone or in combination with DDE─mitochondria form contact sites with a rough endoplasmic reticulum and endo-lysosomes containing nanoparticles. These findings indicate that the protective capability of PtNPs, through their intrinsic antioxidant properties and modulating mitochondrial functionality, is mediated by an inter-organelle crosstalk. This study sheds new light about the protective action mechanisms of PtNPs and discloses a novel nano-biointeraction mechanism at the intracellular level, modulated by inter-organelle communication and signaling.

Keywords: MFN2; ROS; SOD2; antioxidant activity; inter-organelle contact sites; mitochondria; nanozymes; platinum nanoparticles

DOI: https://doi.org/10.1021/acsami.2c22375