Scientists show how mitochondria manages entry and exit doors of calcium, according to a study published on September 18, 2018.
This study was conducted by the scientists at the Thomas Jefferson University. Excess of calcium entering mitochondria will overload the system and lead to cell death. Scientists have a come up with a solution for this in this study.
Since the heart muscle needs ATP to contract, the energy store of heart needs to be regularly replenished by the mitochondria, which means that mitochondria needs just the right amount of calcium to keep the energy factory humming along. Excess of calcium to mitochondria also helps the heart tolerate stress. An accelerated heart rate triggers more calcium to flood the mitochondria. The mitochondria in turn produce more ATP to allow the heart to respond to the stress.
To control the amount of calcium entering its chambers, mitochondria has one-way doors called mitochondrial calcium uniporter channel complexes (MCUCs) that control access. To keep from overloading mitochondria with calcium, the doors remain sealed most of the time. It opens when enough calcium is nearby to unlock them, but calcium needs a door by which to exit as well to keep levels safe.
Calcium exits mitochondria through a revolving door called NCLX, which is a transport protein. Researchers broke up heart cells obtained from male mice to find the exit doors in mitochondria. They found MCUC entry doors alongside the SR calcium store, as they expected, but exit door proteins were almost entirely absent. Instead, the team found the exit doors were abundant only in areas with little to no SR contact, far from the entrances. Researchers found that inserting exit doors close to MCUC entrances cost the mitochondria more energy. Therefore, position of the calcium entrances and exits allow mitochondria to operate at maximum efficiency even when stressed.