Mitochondrial DNA mutations affect calcium handling in differentiated neurons.
Mutations in the mitochondrial genome are associated with a wide range of neurological symptoms, but many aspects of the basic neuronal pathology are not understood. One candidate mechanism, given the well-established role of mitochondria in calcium buffering, is a deficit in neuronal calcium homoeostasis. We therefore examined calcium responses in the neurons derived from various 'cybrid' embryonic stem cell lines carrying different mitochondrial DNA mutations. Brief ( approximately 50 ms), focal glutamatergic stimuli induced a transient rise in intracellular calcium concentration, which was visualized by bulk loading the cells with the calcium dye, Oregon Green BAPTA-1. Calcium entered the neurons through N-methyl-d-aspartic acid and voltage-gated calcium channels, as has been described in many other neuronal classes. Intriguingly, while mitochondrial mutations did not affect the calcium transient in response to single glutamatergic stimuli, they did alter the responses to repeated stimuli, with each successive calcium transient decaying ever more slowly in mitochondrial mutant cell lines. A train of stimuli thus caused intracellular calcium in these cells to be significantly elevated for many tens of seconds. These results suggest that calcium-handling deficits are likely to contribute to the pathological phenotype seen in patients with mitochondrial DNA mutations.
Trevelyan
Andrew J
AJ
Mitochondrial Research Group, Institute for Ageing and Health Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, England. a.j.trevelyan@gmail.com
Kirby
Denise M
DM
Smulders-Srinivasan
Tora K
TK
Nooteboom
Marco
M
Acin-Perez
Rebeca
R
Enriquez
José Antonio
JA
Whittington
Miles A
MA
Lightowlers
Robert N
RN
Turnbull
Doug M
DM
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002460:Cell Line; D004272:DNA, Mitochondrial; D053595:Embryonic Stem Cells; D005260:Female; D005452:Fluoresceins; D018698:Glutamic Acid / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D051379:Mice; D028361:Mitochondrial Diseases / Q000235:genetics* / Q000503:physiopathology*; D009154:Mutation; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013997:Time Factors
D000814:Aniline Compounds; D015220:Calcium Channels; D004272:DNA, Mitochondrial; D005452:Fluoresceins; C503942:Oregon green 488 BAPTA-1; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D002118:Calcium