Bravo-Sagua 2019 MiPschool Coimbra

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Roberto Bravo-Sagua
Caveolin-1 antagonizes PKA in the remodelling of metabolism modulated by ER–mitochondria communication during early ER stress.

Link: MitoEAGLE

Bravo-Sagua R, Parra V, Quest AFG, Lavandero S (2019)

Event: MiPschool Coimbra 2019

COST Action MitoEAGLE

Contact points between the endoplasmic reticulum (ER) and mitochondria enable Ca2+ transfer between both organelles, which is a key mechanism in the modulation of mitochondrial metabolism. During early ER stress, this communication increases as an adaptive mechanism [1]. The signalling pathways controlling this response, however, are yet to be fully characterized. As candidates, we hypothesised that Caveolin-1 (CAV1) may be implicated, as it is enriched at ER–mitochondria contact sites [2]. PKA was also a candidate, as its activity has been shown to regulate organelle dynamics [3].

We used wild type HeLa cells for overexpressing CAV1. Early ER stress was induced with tunicamycin 0,5 µg/mL for 4 h. We measured ER–mitochondria contacts via electron microscopy and confocal microscopy. For Ca2+ transfer, we used the fluorescent probe Rhod-FF. To evaluate mitochondrial respiration, we measured a Clark’s electrode. DRP1 phosphorylation was analysed through western blot. Cell viability was determined though annexin V staining using flow cytometry.

Early ER stress augmented ER–mitochondria contacts, which was prevented by CAV1 overexpression. This rendered ER-to-mitochondria Ca2+ transfer and mitochondrial bioenergetics unresponsive to ER stress. PKA inhibition with H89 or siRNA also impaired the increase in organelle contacts, Ca2+ transfer and mitochondrial respiration. CAV1 overexpression reduced PKA-mediated DRP1 phosphorylation, thereby enhancing ER stress-induced cell death. Increasing ER-mitochondria contacts with a synthetic linker restored cell survival.

Thus, PKA promotes the increase of ER–mitochondria contacts that occurs during ER stress. CAV1, in turn, prevents PKA-mediated phosphorylation, also impairing said remodelling. Increasing ER–mitochondria contacts is necessary for the increase in mitochondrial bioenergetics and cell adaptation to ER stress [4].


Bioblast editor: Plangger M


Labels: MiParea: Respiration, Genetic knockout;overexpression 


Organism: Human  Tissue;cell: HeLa 


Regulation: Calcium 




Affiliations

Bravo-Sagua R(1,2,3), Parra V(3,4,5), Quest AFG(3,5,6), Lavandero S(3,4,5,6,7)
  1. IRB Barcelona, Univ Barcelona, Spain
  2. INTA, Univ Chile; 3ACCDiS, Pontifical Catholic Univ Chile & Univ Chile
  3. Fac Chemical & Pharmaceutical Sciences, Univ Chile
  4. CEMC Univ Chile
  5. ICBM Univ Chile; Santiago, Chile
  6. Dept Internal Medicine, Univ Texas Southwestern Medical Center, Dallas, Texas, United States. - roberto.bravo@irbbarcelona.org

References

  1. Bravo R, Vicencio JM, Parra V, Troncoso R, Munoz JP, Bui M, Quiroga C, Rodriguez AE, Verdejo HE, Ferreira J, Iglewski M, Chiong M, Simmen T, Zorzano A, Hill JA, Rothermel BA, Szabadkai G, Lavandero S (2011) Increased ER-mitochondrial coupling promotes mitochondrial respiration and bioenergetics during early phases of ER stress. J Cell Sci 124:2143-52.
  2. Sala-Vila A, Navarro-Lérida I, Sánchez-Alvarez M, Bosch M, Calvo C, López JA, Calvo E, Ferguson C, Giacomello M, Serafini A, Scorrano L, Enriquez JA, Balsinde J, Parton RG, Vázquez J, Pol A, Del Pozo MA (2016) Interplay between hepatic mitochondria- associated membranes, lipid metabolism and caveolin-1 in mice. Sci Rep 6:27351.
  3. Aguileta MA, Rojas-Rivera D, Goossens V, Estornes Y, Van Isterdael G, Vandenabeele P, Bertrand MJ (2016) A siRNA screen reveals the prosurvival effect of protein kinase A activation in conditions of unresolved endoplasmic reticulum stress. Cell Death Differ 23:1670–80.
  4. Bravo-Sagua R, Parra V, Ortiz-Sandoval C, Navarro-Marquez M, Rodríguez AE, Diaz-Valdivia N, Sanhueza C, Lopez-Crisosto C, Tahbaz N4, Rothermel BA, Hill JA, Cifuentes M, Simmen T, Quest AFG, Lavandero S (2018) Caveolin-1 impairs PKA-DRP1-mediated remodelling of ER-mitochondria communication during the early phase of ER stress. Cell Death Differ 26:1195-212.