Molecular mechanisms underlying CPVT2: calpain as a new potential therapeutic target

• Autores: Laura Ramos Hernández
• Directores de la Tesis: Enrique Lara Pezzi (dir. tes.), Carmen Delgado Canencia (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2023
• Idioma: inglés
• Número de páginas: 152
• Títulos paralelos:
  • Mecanismos moleculares subyacentes a la CPVT2: calpaína como nueva potencial diana terapéutica
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease associated with sudden death in children and young adults. CPVT2 is caused by loss-of-function (LoF) mutations in the gene encoding cardiac calsequestrin (CASQ2), which along with triadin (TRDN) and junctin (JNT) regulates the release of calcium ions from the sarcoplasmic reticulum via the cardiac ryanodine receptor (RyR2). The homozygous mouse model Casq2R33Q/R33Q closely mimics the clinical phenotype of CPVT2 patients. CASQ2, TRDN and JNT levels are markedly reduced and the mechanisms underlying the decrease of these proteins are not fully understood. Currently available treatments are not entirely effective and new therapeutic options for CPVT patients are needed. The aim of this study was to identify the molecular mechanisms regulating the decrease of these proteins in Casq2R33Q/R33Q mice, and to explore their functional involvement in the disease. Mass spectrometry proteomics revealed that Casq2-/- mice have a different adaptive pattern from Casq2R33Q/R33Q mice, suggesting a specific effect of the R33Q mutation. RyR2 inhibition in Casq2R33Q/R33Q mice treated with flecainide showed an increase in CASQ2 and TRDN, suggesting an important role of SR Ca2+ leak in the mechanism underlying their drop. Increased endoplasmic reticulum stress (ER stress) and UPR pathway activity were observed in Casq2R33Q/R33Q mice which also exhibited alterations in the major cellular proteolytic pathways: ubiquitin proteasome system (UPS), autophagy and calpain. Experiments on isolated neonatal cardiomyocytes and adult mice treated with inhibitors of these mechanisms showed that all of them were involved in CASQ2 degradation, whereas TRDN and JNT proteins levels were only increased when calpain was inhibited. Calpain inhibition is the only treatment that increases CASQ2, TRDN and JNT levels. In addition, VT episodes were reduced with this treatment in Casq2R33Q/R33Q mice. Our results suggest that there is a crosstalk between these three proteolytic mechanisms and identified calpain as a new promising therapeutic target for CPVT patients