ABCB7 deficiency increases endoplasmic reticulum mitochondria coupling and mTOR independent autophagy flux in H9c2 cardiomyocytes

Abstract

ABCB7 deficiency during chronic cardiac hypertrophy contribute to mitochondrial dysfunction, metabolic shift and worsens cardiac function. Here, we explored that ABCB7 deficiency contribute to tethering of mito-ER and in turn mitochondrial dysfunction in H9c2 cells. We also investigated the mechanistic link between mitochondrial dysfunction and ABCB7 deficiency in these cells. Knockdown of ABCB7 was performed by siABCB7 plasmids or control vectors using lipofectamine 2000. To rescue the changes produced by siABCB7, ABCB7 overexpression was performed using ABCB7 overexpression vector. After knockdown or overexpression, cells were harvested for transmission electron microscopy (TEM), RT-PCR or Immunofluorescence analysis. Knockdown of ABCB7 in H9C2 cells resulted in enhanced tethering of mito.-ER contact sites, and increased mito.-ER distance. To our surprise, the downregulation of ABCB7 did not alter the cristae structure or morphology in these cells. On the mechanistic front, Knockdown of ABCB7 in H9C2 cells MTOR-independent AMPK-dependent macroautophagic/autophagic flux. ABCB7 downregulation did not result in cell death in these cells; this phenomenon could work independent of cell death in H9c2 cells.