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J Biol Chem. 2015 Sep 11;290(37):22325-36. doi: 10.1074/jbc.M115.656405. Epub 2015 Jun 30.

The role of mitochondrially derived ATP in synaptic vesicle recycling.

Author information

1
From the Gladstone Institute of Neurological Disease, San Francisco, California 94158.
2
From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158.
3
From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Pediatrics, University of California at San Francisco, San Francisco, California 94143, and.
4
the Buck Institute for Research on Aging, Novato, California 94945.
5
the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158.
6
From the Gladstone Institute of Neurological Disease, San Francisco, California 94158, the Department of Neurology and Graduate Programs in Neuroscience and Biomedical Sciences, University of California at San Francisco, San Francisco, California 94158, ken.nakamura@gladstone.ucsf.edu.

Abstract

Synaptic mitochondria are thought to be critical in supporting neuronal energy requirements at the synapse, and bioenergetic failure at the synapse may impair neural transmission and contribute to neurodegeneration. However, little is known about the energy requirements of synaptic vesicle release or whether these energy requirements go unmet in disease, primarily due to a lack of appropriate tools and sensitive assays. To determine the dependence of synaptic vesicle cycling on mitochondrially derived ATP levels, we developed two complementary assays sensitive to mitochondrially derived ATP in individual, living hippocampal boutons. The first is a functional assay for mitochondrially derived ATP that uses the extent of synaptic vesicle cycling as a surrogate for ATP level. The second uses ATP FRET sensors to directly measure ATP at the synapse. Using these assays, we show that endocytosis has high ATP requirements and that vesicle reacidification and exocytosis require comparatively little energy. We then show that to meet these energy needs, mitochondrially derived ATP is rapidly dispersed in axons, thereby maintaining near normal levels of ATP even in boutons lacking mitochondria. As a result, the capacity for synaptic vesicle cycling is similar in boutons without mitochondria as in those with mitochondria. Finally, we show that loss of a key respiratory subunit implicated in Leigh disease markedly decreases mitochondrially derived ATP levels in axons, thus inhibiting synaptic vesicle cycling. This proves that mitochondria-based energy failure can occur and be detected in individual neurons that have a genetic mitochondrial defect.

KEYWORDS:

ATP; axon; bioenergetics; endocytosis; mitochondria

PMID:
26126824
PMCID:
PMC4566209
DOI:
10.1074/jbc.M115.656405
[Indexed for MEDLINE]
Free PMC Article

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