Browsing by Author "Rothermel, Beverly A."
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- ItemDown syndrome critical region 1 gene, rcan1, helps maintain a more fused mitochondrial network(2018) Parra, Valentina; Altamirano, Francisco; Hernández Fuentes, Carolina P.; Tong, Dan; Kyrychenko, Victoriia; Rotter, David; Pedrozo, Zully; Hill, Joséph A.| Eisner Sagüés, Verónica Raquel; Lavandero, Sergio; Schneider, Jay W.; Rothermel, Beverly A.
- ItemEndoplasmic reticulum-mitochondria coupling increases during doxycycline-induced mitochondrial stress in HeLa cells(2021) Lopez-Crisosto, Camila; Diaz-Vegas, Alexis; Castro, Pablo F.; Rothermel, Beverly A.; Bravo-Sagua, Roberto; Lavandero, SergioSubcellular organelles communicate with each other to regulate function and coordinate responses to changing cellular conditions. The physical-functional coupling of the endoplasmic reticulum (ER) with mitochondria allows for the direct transfer of Ca2+ between organelles and is an important avenue for rapidly increasing mitochondrial metabolic activity. As such, increasing ER-mitochondrial coupling can boost the generation of ATP that is needed to restore homeostasis in the face of cellular stress. The mitochondrial unfolded protein response (mtUPR) is activated by the accumulation of unfolded proteins in mitochondria. Retrograde signaling from mitochondria to the nucleus promotes mtUPR transcriptional responses aimed at restoring protein homeostasis. It is currently unknown whether the changes in mitochondrial-ER coupling also play a role during mtUPR stress. We hypothesized that mitochondrial stress favors an expansion of functional contacts between mitochondria and ER, thereby increasing mitochondrial metabolism as part of a protective response. Hela cells were treated with doxycycline, an antibiotic that inhibits the translation of mitochondrial-encoded proteins to create protein disequilibrium. Treatment with doxycycline decreased the abundance of mitochondrial encoded proteins while increasing expression of CHOP, C/EBP beta, ClpP, and mtHsp60, markers of the mtUPR. There was no change in either mitophagic activity or cell viability. Furthermore, ER UPR was not activated, suggesting focused activation of the mtUPR. Within 2 h of doxycycline treatment, there was a significant increase in physical contacts between mitochondria and ER that was distributed throughout the cell, along with an increase in the kinetics of mitochondrial Ca2+ uptake. This was followed by the rise in the rate of oxygen consumption at 4 h, indicating a boost in mitochondrial metabolic activity. In conclusion, an early phase of the response to doxycycline-induced mitochondrial stress is an increase in mitochondrial-ER coupling that potentiates mitochondrial metabolic activity as a means to support subsequent steps in the mtUPR pathway and sustain cellular adaptation.
- ItemER-to-mitochondria miscommunication and metabolic diseases(2015) López Crisosto, Camila; Bravo Sagua, Roberto; Rodriguez Peña, Marcelo; Mera, Claudia; Castro Gálvez, Pablo Federico; Quest, Andrew F. G.; Rothermel, Beverly A.; Cifuentes, Mariana; Lavandero, Sergio
- ItemIncreased ER-mitochondrial coupling promotes mitochondrial respiration and bioenergetics during early phases of ER stress(COMPANY BIOLOGISTS LTD, 2011) Bravo, Roberto; Miguel Vicencio, Jose; Parra, Valentina; Troncoso, Rodrigo; Pablo Munoz, Juan; Bui, Michael; Quiroga, Clara; Rodriguez, Andrea E.; Verdejo, Hugo E.; Ferreira, Jorge; Iglewski, Myriam; Chiong, Mario; Simmen, Thomas; Zorzano, Antonio; Hill, Joseph A.; Rothermel, Beverly A.; Szabadkai, Gyorgy; Lavandero, SergioIncreasing evidence indicates that endoplasmic reticulum (ER) stress activates the adaptive unfolded protein response (UPR), but that beyond a certain degree of ER damage, this response triggers apoptotic pathways. The general mechanisms of the UPR and its apoptotic pathways are well characterized. However, the metabolic events that occur during the adaptive phase of ER stress, before the cell death response, remain unknown. Here, we show that, during the onset of ER stress, the reticular and mitochondrial networks are redistributed towards the perinuclear area and their points of connection are increased in a microtubule-dependent fashion. A localized increase in mitochondrial transmembrane potential is observed only in redistributed mitochondria, whereas mitochondria that remain in other subcellular zones display no significant changes. Spatial re-organization of these organelles correlates with an increase in ATP levels, oxygen consumption, reductive power and increased mitochondrial Ca2+ uptake. Accordingly, uncoupling of the organelles or blocking Ca2+ transfer impaired the metabolic response, rendering cells more vulnerable to ER stress. Overall, these data indicate that ER stress induces an early increase in mitochondrial metabolism that depends crucially upon organelle coupling and Ca2+ transfer, which, by enhancing cellular bioenergetics, establishes the metabolic basis for the adaptation to this response.
- ItemInsulin Stimulates Mitochondrial Fusion and Function in Cardiomyocytes via the Akt-mTOR-NF kappa B-Opa-1 Signaling Pathway(AMER DIABETES ASSOC, 2014) Parra, Valentina; Verdejo, Hugo E.; Iglewski, Myriam; del Campo, Andrea; Troncoso, Rodrigo; Jones, Deborah; Zhu, Yi; Kuzmicic, Jovan; Pennanen, Christian; Lopez Crisosto, Camila; Jana, Fabian; Ferreira, Jorge; Noguera, Eduard; Chiong, Mario; Bernlohr, David A.; Klip, Amira; Hill, Joseph A.; Rothermel, Beverly A.; Abel, Evan Dale; Zorzano, Antonio; Lavandero, SergioInsulin regulates heart metabolism through the regulation of insulin-stimulated glucose uptake. Studies have indicated that insulin can also regulate mitochondrial function. Relevant to this idea, mitochondrial function is impaired in diabetic individuals. Furthermore, the expression of Opa-1 and mitofusins, proteins of the mitochondrial fusion machinery, is dramatically altered in obese and insulin-resistant patients. Given the role of insulin in the control of cardiac energetics, the goal of this study was to investigate whether insulin affects mitochondrial dynamics in cardiomyocytes. Confocal microscopy and the mitochondrial dye MitoTracker Green were used to obtain three-dimensional images of the mitochondrial network in cardiomyocytes and L6 skeletal muscle cells in culture. Three hours of insulin treatment increased Opa-1 protein levels, promoted mitochondrial fusion, increased mitochondrial membrane potential, and elevated both intracellular ATP levels and oxygen consumption in cardiomyocytes in vitro and in vivo. Consequently, the silencing of Opa-1 or Mfn2 prevented all the metabolic effects triggered by insulin. We also provide evidence indicating that insulin increases mitochondrial function in cardiomyocytes through the Akt-mTOR-NFB signaling pathway. These data demonstrate for the first time in our knowledge that insulin acutely regulates mitochondrial metabolism in cardiomyocytes through a mechanism that depends on increased mitochondrial fusion, Opa-1, and the Akt-mTOR-NFB pathway.
- ItemmTOR inhibition triggers mitochondrial fragmentation in cardiomyocytes through proteosome-dependent prohibitin degradation and OPA-1 cleavage(Springer Nature, 2025) Verdejo Pinochet, Hugo; Parra, Valentina; Campo Sfeir, Andrea del; Vasquez-Trincado, Cesar; Gatica, Damian; Lopez-Crisosto, Camila; Kuzmicic Previtali, Jovan Paolo; Venegas-Zamora, Leslye; Zuñiga-Cuevas, Ursula; Troncoso, Mayarling F.; Troncoso, Rodrigo; Rothermel, Beverly A.; Chiong L., Mario; Abel, E. D.; Lavandero, SergioIntroduction Cardiac mitochondrial function is intricately regulated by various processes, ultimately impacting metabolic performance. Additionally, protein turnover is crucial for sustained metabolic homeostasis in cardiomyocytes. Objective Here, we studied the role of mTOR in OPA-1 cleavage and its consequent effects on mitochondrial dynamics and energetics in cardiomyocytes. Results Cultured rat cardiomyocytes treated with rapamycin for 6–24 h showed a significant reduction in phosphorylation of p70S6K, indicative of sustained inhibition of mTOR. Structural and functional analysis revealed increased mitochondrial fragmentation and impaired bioenergetics characterized by decreases in ROS production, oxygen consumption, and cellular ATP. Depletion of either the mitochondrial protease OMA1 or the mTOR regulator TSC2 by siRNA, coupled with an inducible, cardiomyocyte-specific knockout of mTOR in vivo, suggested that inhibition of mTOR promotes mitochondrial fragmentation through a mechanism involving OMA1 processing of OPA-1. Under homeostatic conditions, OMA1 activity is kept under check through an interaction with microdomains in the inner mitochondrial membrane that requires prohibitin proteins (PHB). Loss of these microdomains releases OMA1 to cleave its substrates. We found that rapamycin both increased ubiquitination of PHB1 and decreased its abundance, suggesting proteasomal degradation. Consistent with this, the proteasome inhibitor MG-132 maintained OPA-1 content in rapamycin-treated cardiomyocytes. Using pharmacological activation and inhibition of AMPK our data supports the hypothesis that this mTOR-PHB1-OMA-OPA-1 pathway impacts mitochondrial morphology under stress conditions, where it mediates dynamic changes in metabolic status. Conclusions These data suggest that mTOR inhibition disrupts mitochondrial integrity in cardiomyocytes by promoting the degradation of prohibitins and OPA-1, leading to mitochondrial fragmentation and metabolic dysfunction, particularly under conditions of metabolic stress.
- ItemProtection of the myocardium against ischemia/reperfusion injury by angiotensin-(1–9) through an AT2R and Akt-dependent mechanism(2018) Mendoza Torres, Evelyn; Riquelme, Jaime A.; Vielma Zuñiga, Alejandra Loreto; Ramírez Sagredo, Andrea; Gabrielli, Luigi; Bravo Sagua, Roberto; Jalil Milad, Jorge; Rothermel, Beverly A.; Sánchez, Gina; Ocaranza, María Paz; Lavandero, Sergio
- ItemThe complex interplay between mitochondrial dynamics and cardiac metabolism(2011) Parra, Valentina; Verdejo Pinochet, Hugo; Del Campo, Andrea; Pennanen, Christian; Kuzmicic, Jovan; Iglewski, Myriam; Hill, Joséph A; Rothermel, Beverly A.; Lavandero, Sergio