Super-resolution microscopy reveals that Na+/K+-ATPase signaling protects against glucose-induced apoptosis by deactivating Bad

Cell Death Dis. 2021 Jul 27;12(8):739. doi: 10.1038/s41419-021-04025-8.

Abstract

Activation of the apoptotic pathway is a major cause of progressive loss of function in chronic diseases such as neurodegenerative and diabetic kidney diseases. There is an unmet need for an anti-apoptotic drug that acts in the early stage of the apoptotic process. The multifunctional protein Na+,K+-ATPase has, in addition to its role as a transporter, a signaling function that is activated by its ligand, the cardiotonic steroid ouabain. Several lines of evidence suggest that sub-saturating concentrations of ouabain protect against apoptosis of renal epithelial cells, a common complication and major cause of death in diabetic patients. Here, we induced apoptosis in primary rat renal epithelial cells by exposing them to an elevated glucose concentration (20 mM) and visualized the early steps in the apoptotic process using super-resolution microscopy. Treatment with 10 nM ouabain interfered with the onset of the apoptotic process by inhibiting the activation of the BH3-only protein Bad and its translocation to mitochondria. This occurred before the pro-apoptotic protein Bax had been recruited to mitochondria. Two ouabain regulated and Akt activating Ca2+/calmodulin-dependent kinases were found to play an essential role in the ouabain anti-apoptotic effect. Our results set the stage for further exploration of ouabain as an anti-apoptotic drug in diabetic kidney disease as well as in other chronic diseases associated with excessive apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis* / drug effects
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cytoprotection* / drug effects
  • Cytosol / metabolism
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Glucose / toxicity*
  • Kidney / pathology
  • Male
  • Microscopy*
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Models, Biological
  • Ouabain / pharmacology
  • Protein Binding / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats, Sprague-Dawley
  • Signal Transduction* / drug effects
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Time Factors
  • bcl-2-Associated X Protein / metabolism
  • bcl-Associated Death Protein / metabolism*
  • bcl-X Protein / metabolism

Substances

  • bcl-2-Associated X Protein
  • bcl-Associated Death Protein
  • bcl-X Protein
  • Ouabain
  • Proto-Oncogene Proteins c-akt
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Sodium-Potassium-Exchanging ATPase
  • Glucose