Chromaffin-cell stimulation triggers fast millimolar mitochondrial Ca2+ transients that modulate secretion

Abstract

Activation of calcium-ion (

Mitochondria and chromaffin cell function

“…Our results suggest the existence of two different mitochondrial pools, M1 and M2, which take up Ca 2+ at very different rates in response to activation of VOOCs. Pool M1 takes up Ca 2+ at a rate of about 50 μM/s, 30% of uniporter's V max , whereas uptake by pool M2 is about 150 times slower [36,55]. According to the saturation kinetics parameters measured in chromaffin cells mitochondria, this corresponds to the rates obtained at about 20 and 2 μM [Ca 2+ ] C , respectively.…”

“…We have studied the kinetics of uptake by mitochondria in permeabilized bovine chromaffin cells infected with mitochondria-targeted aequorin probes [36,55]. Measured mitochondrial uptake nicely fitted to the equation…”

“…It has been repeatedly reported that mitochondria can clear cytosolic Ca 2+ loads in rat [11,29,57] and bovine chromaffin cells [36,55,60]. We have studied the kinetics of uptake by mitochondria in permeabilized bovine chromaffin cells infected with mitochondria-targeted aequorin probes [36,55].…”

“…Chromaffin cell mitochondria accumulate large amounts of Ca 2+ during stimulation with either high K + solutions, acetylcholine or caffeine [36]. Ca 2+ is taken up through the mitochondrial Ca 2+ uniporter (MCU), a protein associated to the inner mitochondrial membrane that has been cloned recently [12,19] (Fig.…”

Calcium dynamics in the secretory granules of neuroendocrine cells

“…In particular, because of the low-Ca 2+ -affinity of their Ca 2+ uptake mechanism, mitochondria are very well adapted to take up Ca 2+ from local high-Ca 2+ microdomains, such as those formed after the activation of plasma membrane or endoplasmic reticulum Ca 2+ channels. Mitochondria can therefore modulate important cellular functions such as neurotransmitter secretion by acting as local Ca 2+ sinks [5].…”