Cellular stress is a prerequisite for glucose-induced mitochondrial matrix alkalinization in pancreatic β-cells

• Published in: Molecular and cellular endocrinology 2019-02, Vol.481, p.71-83
• Main Authors: Chareyron, Isabelle, Wall, Christopher, Thevenet, Jonathan, Santo-Domingo, Jaime, Wiederkehr, Andreas
• Format: Article
• Language: English
• Subjects: Adenoviridae - genetics; Animals; Beta-cells; Cells, Cultured; Energy metabolism; Genes, Reporter; Glucose - pharmacology; Human islets; Humans; Hydrogen-Ion Concentration; Insulin - genetics; Insulin-Secreting Cells - cytology; Insulin-Secreting Cells - drug effects; Insulin-Secreting Cells - metabolism; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Membrane Potential, Mitochondrial - drug effects; Metabolism-secretion coupling; Mitochondria; Mitochondrial Membranes - chemistry; Mitochondrial Membranes - drug effects; Promoter Regions, Genetic; Rats; Transfection
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/j.mce.2018.11.011

Changes in mitochondrial and cytosolic pH alter the chemical gradient across the inner mitochondrial membrane. The proton chemical gradient contributes to mitochondrial ATP synthesis as well as the uptake and release of metabolites and ions from the organelle. Here mitochondrial pH and ΔpH were studied for the first time in human pancreatic β-cells. Adenoviruses were used for rat insulin promoter dependent expression of the pH sensor SypHer targeted to either the mitochondrial matrix or the cytosol. The matrix pH in resting human β-cells is low (pH = 7.50 ± SD 0.17) compared to published values in other cell types. Consequently, the ΔpH of β-cells mitochondria is small. Glucose stimulation consistently resulted in acidification of the matrix pH in INS-1E insulinoma cells and β-cells in intact human islets or islet monolayer cultures. We registered acidification with similar kinetics but of slightly smaller amplitude in the cytosol of β-cells, thus glucose stimulation further reduced the ΔpH. Infection of human islets with high levels of adenoviruses caused the mitochondrial pH to increase. The apoptosis inducer and broad-spectrum kinase inhibitor staurosporine had similar effects on pH homeostasis. Although staurosporine alone does not affect the mitochondrial pH, glucose slightly increases the matrix pH of staurosporine treated cells. These two cellular stressors alter the normal mitochondrial pH response to glucose in pancreatic β-cells. [Display omitted] •Developed RIP-mitoSypHer adenovirus for mitochondrial pH measurement in pancreatic beta-cells.•First measurement of mitochondrial pH in human islet beta-cells.•Transient acidification of matrix pH in response to glucose.•Stress conditions can affect mitochondrial pH responses to glucose.