What has this got to do with MS you ask?
Calcium overload is part of the mechanism of how cells die and we saw recently that the creation of a channel between the protein synthesis and calcium-ion producing endoplasmic reticulum and the mitochondria, made the mitochondria vulnerable to failure and nerve dead. The calcium sodium exchanger in the mitochondria (powerhouses of cells) pumps in sodium and pumps out calcium. In the cell membrane it pumps in sodium and pumps out calcium, until there is too much sodium in the cell when it pulls in calcium and the cell dies. This can be blocked by blockage of the mitochondrial permeability transition pore activation.
The Mitochondrial permeability transition pore is a protein that is formed in the inner membrane of the mitochondria under certain pathological conditions such as MS. Opening allows increase in the permeability of the mitochondrial membranes that can lead to mitochondrial swelling and cell death through apoptosis or necrosis depending on the particular biological setting.