Browsing by Author "Norambuena-Soto, Ignacio"

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    Angiotensin II-Regulated Autophagy Is Required for Vascular Smooth Muscle Cell Hypertrophy
    (2019) Mondaca-Ruff, David; Riquelme, Jaime A.; Quiroga Lagos, Clara Rosa; Norambuena-Soto, Ignacio; Sanhueza-Olivares, Fernanda; Villar-Fincheira, Paulina; Hernández-Díaz,Tomás; Cancino-Arenas, Nicole; San Martín, Alejandra; García, Lorena; Lavandero, Sergio; Chiong, Mario
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    Polycystin-1 regulates cardiomyocyte mitophagy
    (2021) Ramirez-Sagredo, Andrea; Quiroga, Clara; Garrido-Moreno, Valeria; Lopez-Crisosto, Camila; Leiva-Navarrete, Sebastian; Norambuena-Soto, Ignacio; Ortiz-Quintero, Jafet; Diaz-Vesga, Magda C.; Perez, William; Hendrickson, Troy; Parra, Valentina; Pedrozo, Zully; Altamirano, Francisco; Chiong, Mario; Lavandero, Sergio
    Polycystin-1 (PC1) is a transmembrane protein found in different cell types, including cardiomyocytes. Alterations in PC1 expression have been linked to mitochondrial damage in renal tubule cells and in patients with autosomal dominant polycystic kidney disease. However, to date, the regulatory role of PC1 in cardiomyocyte mitochondria is not well understood. The analysis of mitochondrial morphology from cardiomyocytes of heterozygous PC1 mice (PDK1(+/-)) using transmission electron microscopy showed that cardiomyocyte mitochondria were smaller with increased mitochondria density and circularity. These parameters were consistent with mitochondrial fission. We knocked-down PC1 in cultured rat cardiomyocytes and human-induced pluripotent stem cells (iPSC)-derived cardiomyocytes to evaluate mitochondrial function and morphology. The results showed that downregulation of PC1 expression results in reduced protein levels of sub-units of the OXPHOS complexes and less functional mitochondria (reduction of mitochondrial membrane potential, mitochondrial respiration, and ATP production). This mitochondrial dysfunction activates the elimination of defective mitochondria by mitophagy, assessed by an increase of autophagosome adapter protein LC3B and the recruitment of the Parkin protein to the mitochondria. siRNA-mediated PC1 knockdown leads to a loss of the connectivity of the mitochondrial network and a greater number of mitochondria per cell, but of smaller sizes, which characterizes mitochondrial fission. PC1 silencing also deregulates the AKT-FoxO1 signaling pathway, which is involved in the regulation of mitochondrial metabolism, mitochondrial morphology, and processes that are part of cell quality control, such as mitophagy. Together, these data provide new insights about the controls that PC1 exerts on mitochondrial morphology and function in cultured cardiomyocytes dependent on the AKT-FoxO1 signaling pathway.
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    Regulation of total LC3 levels by angiotensin II in vascular smooth muscle cells
    (2022) Mondaca-Ruff, David; Quiroga, Clara; Norambuena-Soto, Ignacio; Riquelme, Jaime A.; San Martin, Alejandra; Bustamante, Mario; Lavandero, Sergio; Chiong, Mario
    Hypertension is associated with high circulating angiotensin II (Ang II). We have reported that autophagy regulates Ang II-induced vascular smooth muscle cell (VSMC) hypertrophy, but the mechanism mediating this effect is still unknown. Therefore, we studied how Ang II regulates LC3 levels in VSMCs and whether Bag3, a co-chaperone known to regulate LC3 total levels, may be involved in the effects elicited by Ang II. A7r5 cell line or rat aortic smooth muscle cell (RASMC) primary culture were stimulated with Ang II 100 nM for 24 h and LC3 I, LC3 II and Bag3 protein levels were determined by Western blot. MAP1LC3B mRNA levels were assessed by RT-qPCR. Ang II increased MAP1LC3B mRNA levels and protein levels of LC3 I, LC3 II and total LC3 (LC3 I + LC3 II). Cycloheximide, but not actinomycin D, abolished LC3 II and total LC3 increase elicited by Ang II in RASMCs. In A7r5 cells, cycloheximide prevented the Ang II-mediated increase of LC3 I and total LC3, but not LC3 II. Moreover, Ang II increased Bag3 levels, but this increase was not observed upon co-administration with either losartan 1 mu M (AT1R antagonist) or Y-27632 10 mu M (ROCK inhibitor). These results suggest that Ang II may regulate total LC3 content through transcriptional and translational mechanisms. Moreover, Bag3 is increased in response to Ang II by a AT1R/ROCK signalling pathway. These data provide preliminary evidence suggesting that Ang II may stimulate autophagy in VSMCs by increasing total LC3 content and LC3 processing.