Biology subjects

Covarrubias, L.

Publications and source records attributed to Covarrubias, L..

3 recordsLinked to original sources

bioRxiv2023

Macrophages allocate before apoptosis initiation and produce reactive oxygen species during interdigital phagocytosis

During programmed cell death (PCD), it is commonly accepted that macrophages are recruited by apoptotic cells to complete cell degradation. Interdigital cell death, a classical model of PCD, contributes to digit individualization in limbs of mammals and other vertebrates. Here we show that macrophages are present in interdigits before significant cell death occurs and remain after apoptosis inhibition. The typical interdigital phagocytic activity was not observed after a partial depletion of macrophages and was markedly reduced by engulfment/phagosome maturation inhibition, as detected by its association with high lysosomal activity. {beta}-galactosidase activity in this region was also coupled with phagocytosis, against its relationship with cellular senescence. Interdigital phagocytosis correlated with high levels of reactive oxygen species (ROS), common in embryo regions carrying abundant cell death, suggesting that macrophages are the major source of ROS. ROS generation was dependent on NADPH oxidases and blood vessel integrity, but not directly associated with lysosomal activity. Therefore, macrophages prepattern regions where abundant cell death is going to occur, and high lysosomal activity and the generation of ROS by an oxidative burst-like phenomenon are activities of phagocytosis. Summary statementRecruitment of macrophages to the interdigital regions is not linked to apoptosis initiation and they phagocytize by a mechanism involving high lysosomal activity and an oxidative burst-like phenomenon.

developmental biology↗

bioRxiv2023

The loss of antioxidant activities impairs intestinal epithelium homeostasis by altering lipid metabolism

The increase in reactive oxygens species (ROS) with aging could be at the origin of many diseases of the elderly. Here we investigated the role of ROS in the renewal of the intestinal epithelium in mice lacking catalase (CAT) and/or nicotinamide nucleotide transhydrogenase (NNT) activities. Cat-/- mice have delayed intestinal epithelium renewal and were prone to develop necrotizing enterocolitis upon starvation. Interestingly, crypts lacking CAT showed fewer intestinal stem cells (ISC) and lower stem cell activity than wild-type, together with less LYS in Paneth cells. In contrast, crypts lacking NNT showed a similar number of ISCs and amount of LYS as wild-type but increased stem cell activity, which was also impaired by the loss of CAT. Cat deficiency caused fat accumulation in crypts, and a fall in the remarkable high amount of adipose triglyceride lipase (ATGL) in PCs. Supporting a role of ATGL in the regulation of ISC activity, its inhibition halt intestinal organoid development. These data suggest that the reduction of the intestine renewal capacity along aging originates from fatty acid metabolic alterations caused by peroxisomal ROS. Summary statementMice with increased peroxisomal or mitochondrial reactive oxygen species develop intestinal phenotypes that are associated with aging and originate from a defective stem cell niche with impaired fatty acid metabolism.

molecular biology↗

bioRxiv2019

The nuclear receptor NR4A1 is regulated by SUMO modification to induce autophagic cell death

NR4A is a nuclear receptor protein family whose members act as sensors of cellular environment and regulate multiple processes such as metabolism, proliferation, migration, apoptosis, and autophagy. Since the ligand binding domains of these receptors have no cavity for ligand interaction, their function is most likely regulated by protein abundance and post-translational modifications. In particular, NR4A1 is regulated by protein abundance, phosphorylation, and subcellular distribution (nuclear-cytoplasmic translocation), and acts both as a transcription factor and as a regulator of other interacting proteins. SUMOylation is a post-translational modification that can affect protein stability, transcriptional activity, alter protein-protein interactions and modify intracellular localization of target proteins. In the present study we evaluated the role of SUMOylation as a posttranslational modification that can regulate the activity of NR4A1 to induce autophagy-dependent cell death. We focused on a model potentially relevant for neuronal cell death and demonstrated that NR4A1 needs to be SUMOylated to induce autophagic cell death. We observed that a triple mutant in SUMOylation sites has reduced SUMOylation, increased transcriptional activity, altered intracellular distribution, and more importantly, its ability to induce autophagic cell death is impaired.\n\nSummary StatementThe modification of the nuclear receptor NR4A1 by SUMO regulates its transcriptional activity, intracellular localization and is required to induce autophagic cell death.

biochemistry↗