Mitochondria play a central role in cell metabolism and control multiple aspects of neuronal signaling. By efficiently buffering Ca2+ influx during neuronal excitation and slowly releasing Ca2+ back into the cytosol, mitochondria shape [Ca2+]i transients and regulate Ca2+-dependent neuronal functions, such as excitability, synaptic transmission and gene expression. Ca2+ rise in the mitochondrial matrix stimulates Ca2+-dependent dehydrogenases and boosts ATP production to meet the increase in energy demand during excitation. However, mitochondrial overload with Ca2+ can kill neurons, and mitochondrial Ca2+ dysregulation is implicated in neuronal damage during stroke and in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases. Despite the importance of mitochondrial Ca2+ transport to neuronal life and death, the molecules that mediate mitochondrial Ca2+ uptake and release in neurons are not known. This knowledge gap presents a major obstacle in our progress toward understanding and therapeutically correcting mitochondrial functions in neurons. The main objectives of this proposal are to identify molecules that mediate mitochondrial Ca2+ uptake in peripheral and central neurons, and to establish their roles in neuronal Ca2+ signaling, ATP synthesis, synaptic transmission and excitotoxicity. Our preliminary studies indicate that two novel molecules, MCU (CCDC109A) and MCUb (CCDC109B), are broadly expressed in the peripheral and central nervous systems, and that MCU is required for mitochondrial Ca2+ uptake in neurons whereas MCUb inhibits this Ca2+ transport mechanism. Moreover, our pilot data using MCU KO mice showed that MCU loss dramatically, but not completely, reduced mitochondrial Ca2+ uptake, altered Ca2+ signaling and mitochondrial function and provided remarkable protection against glutamate-induced toxicity. Our central hypothesis is that MCU and MCUb play important but opposite roles in the regulation of mitochondrial Ca2+ uptake in neurons, bioenergetics, Ca2+ signaling and synaptic transmission, and that knockout of MCU, but not of MCUb, protects neurons from excitotoxicity and reduces neuronal damage in ischemic stroke. We will employ a multidisciplinary approach involving genetic Ca2+ and ATP sensors, patch-clamp recording, knockout mice and a mouse model of ischemic stroke to test this hypothesis in three specific aims.
Aim 1 will establish the roles of MCU and MCUb in mitochondrial Ca2+ transport and Ca2+ signaling in central and peripheral neurons.
Aim 2 will examine the impact of MCU and MCUb on presynaptic Ca2+ signaling and synaptic transmission.
Aim 3 will establish the roles of MCU and MCUb in excitotoxicity and ischemic stroke. We anticipate that this work will be transformative because it will establish the molecular basis for genetic and pharmacological manipulation of mitochondrial Ca2+ transport in neurons, and may lead to the development of new therapeutics that target mitochondrial Ca2+ uniporters for treating stroke and other neurological disorders associated with excitotoxicity.

Public Health Relevance

Mitochondrial Ca2+ uptake plays important role in neuronal signaling and ATP production. However mitochondrial overload with Ca2+ and deregulation of Ca2+ signaling are implicated in neuronal damage in stroke and neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The proposed studies will help to better understand how novel components of mitochondrial Ca2+ uptake, MCU and MCUb, contribute to neuronal Ca2+ signaling, synaptic transmission and neuronal toxicity, and may lead to the development of new therapeutic strategies for neuroprotection in stroke and neurodegenerative disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS096246-05
Application #
9996358
Study Section
Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
Program Officer
Bosetti, Francesca
Project Start
2016-09-01
Project End
2021-08-31
Budget Start
2020-09-01
Budget End
2021-08-31
Support Year
5
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Iowa
Department
Pharmacology
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
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Hamilton, James; Brustovetsky, Tatiana; Rysted, Jacob E et al. (2018) Deletion of mitochondrial calcium uniporter incompletely inhibits calcium uptake and induction of the permeability transition pore in brain mitochondria. J Biol Chem 293:15652-15663
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