Special features of mitochondrial Ca2+ signalling in adrenal glomerulosa cells

Aldosterone, secreted by adrenal glomerulosa cells, allows the adaptation of the vertebrate organism to a wide range of physiological and pathological stimuli including acute haemodynamic challenges and long-term changes in dietary sodium and potassium intake. Most of the extracellular signals are mediated by cytosolic Ca2+ signal deriving from Ca2+ release, store-operated and/or voltage-gated Ca2+ influx. Mitochondria in glomerulosa cells play a fundamental role in generating and modulating the final biological response. These organelles not only house several enzymes of aldosterone biosynthesis but also—in a Ca2+-dependent manner—provide NADPH for the function of these enzymes. Moreover, mitochondria, constituting a high portion of cytoplasmic volume and displaying a uniquely low-threshold Ca2+ sequestering ability, shape and thus modulate the decoding of the complex cytosolic Ca2+ response. The unusual features of mitochondrial Ca2+ signalling that permit such an integrative function in adrenal glomerulosa cells are hereby described.