Our overall goal is to determine the mitochondrial mechanisms that influence neurotransmitter release and the impact of these mechanisms across different synapse types. Mitochondria in nerve terminals are well placed to influence neurotransmitter release but their means of influence have resisted clarification. Many facets of mitochondrial function have been directly implicated in synaptic plasticity but due to the interwoven nature of these activities (ATP production;Ca2+ and Na+ handling;extrusion of protons;release of reactive oxygen species) it has been difficult to identify those that make the primary impact. A second area that requires clarification is the role of mitochondria in different forms of short-term synaptic plasticity. Although mitochondria have an established role in the post-tetanic potentiation of synaptic strength, little is known about their impact on other forms of short-term synaptic plasticity. Lastly, while we know that mitochondria influence neurotransmitter release and synaptic plasticity in large nerve terminals very little is known about their influence in small terminals, typical of the mammalian CNS. These are glaring gaps in our knowledge, particularly as synaptic plasticity allows for changes in synaptic strength, a phenomenon underlying learning and memory. More troubling perhaps, is that mitochondrial dysfunction is found at the epicenter of many neurodegenerative conditions for which the pathogenesis and progression are poorly understood. The central hypothesis is that mitochondria influence neurotransmitter release through multiple mechanisms, and the architecture of the nerve terminal and its firing history determines which mechanism is influential. We bring a combined electrophysiological, imaging and genetic approach to address this hypothesis at Drosophila nerve terminals in vivo, and we introduce a novel peripheral synapse with a single release-site as a model for central synapses with the same architecture. We will test the ability of mitochondrial Ca2+ uptake to limit the amplitude of Ca2+ transients and neurotransmitter release during short trains of action potentials - a firing pattern common in central neurons (Aim 1). Emphasis will be placed on single release-site nerve terminals where we observe mitochondria to have a voracious appetite for Ca2+. We will determine if mitochondria in these terminals are more effective at taking up Ca2+ because they are able to take up Ca2+ directly from Ca2+ microdomains (Aim 2). We will determine whether mitochondrial ATP production, rather than Ca2+ uptake, is the principle mechanism that maintains synchronous release during sustained nerve firing (Aim 3). Finally we will test the requirement for mitochondrial Ca2+ release in the post-tetanic potentiation of transmitter release, and examine the transfer of Ca2+ between mitochondria and the endoplasmic reticulum (Aim 4). An understanding of how mitochondrial function influences synaptic transmission under non-pathological conditions will provide the foundation required to understand the role of mitochondria in pathological conditions.

Public Health Relevance

Mitochondria are organelles within all cells of the human body that generate most of our energy. They concentrate within nerve endings where they power communication between nerves, a fundamental activity of the brain. However, little is known about the way in which they contribute to the function of the nervous system and this is troubling, as mitochondrial malfunction is implicated in many diseases of the nervous system. We are currently examining how mitochondria influence the communication between healthy nerves so that we may understand the ways in which they may become involved in neurodegenerative conditions.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
Project #
Application #
Study Section
Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
Program Officer
Talley, Edmund M
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Health Science Center San Antonio
Schools of Medicine
San Antonio
United States
Zip Code
Stawarski, Michal; Justs, Karlis Anthony; Hernandez, Roberto Xander et al. (2018) The application of 'kisser' probes for resolving the distribution and microenvironment of membrane proteins in situ. J Neurogenet 32:236-245
Rossano, Adam J; Kato, Akira; Minard, Karyl I et al. (2017) Na+ /H+ exchange via the Drosophila vesicular glutamate transporter mediates activity-induced acid efflux from presynaptic terminals. J Physiol 595:805-824
Ugur, Berrak; Bao, Huan; Stawarski, Michal et al. (2017) The Krebs Cycle Enzyme Isocitrate Dehydrogenase 3A Couples Mitochondrial Metabolism to Synaptic Transmission. Cell Rep 21:3794-3806
Lu, Zhongmin; Chouhan, Amit K; Borycz, Jolanta A et al. (2016) High-Probability Neurotransmitter Release Sites Represent an Energy-Efficient Design. Curr Biol 26:2562-2571
Sakellariou, Giorgos K; Davis, Carol S; Shi, Yun et al. (2014) Neuron-specific expression of CuZnSOD prevents the loss of muscle mass and function that occurs in homozygous CuZnSOD-knockout mice. FASEB J 28:1666-81
Wong, Ching-On; Chen, Kuchuan; Lin, Yong Qi et al. (2014) A TRPV channel in Drosophila motor neurons regulates presynaptic resting Ca2+ levels, synapse growth, and synaptic transmission. Neuron 84:764-77
Grygoruk, Anna; Chen, Audrey; Martin, Ciara A et al. (2014) The redistribution of Drosophila vesicular monoamine transporter mutants from synaptic vesicles to large dense-core vesicles impairs amine-dependent behaviors. J Neurosci 34:6924-37
Shi, Yun; Ivannikov, Maxim V; Walsh, Michael E et al. (2014) The lack of CuZnSOD leads to impaired neurotransmitter release, neuromuscular junction destabilization and reduced muscle strength in mice. PLoS One 9:e100834
Daniels, Richard W; Rossano, Adam J; Macleod, Gregory T et al. (2014) Expression of multiple transgenes from a single construct using viral 2A peptides in Drosophila. PLoS One 9:e100637
Ivannikov, Maxim V; Macleod, Gregory T (2013) Mitochondrial free Ca²? levels and their effects on energy metabolism in Drosophila motor nerve terminals. Biophys J 104:2353-61

Showing the most recent 10 out of 22 publications