Huang, FD (reprint author), Chinese Acad Sci, Inst Neurosci, Shanghai Inst Biol Sci, 320 Yue Yang Rd, Shanghai 200031, Peoples R China,email@example.com
Alzheimer's disease (AD) is attributable to synapse dysfunction and loss, but the nature and progression of the presynaptic structural and functional changes in AD are essentially unknown. We expressed wild-type or arctic form of beta amyloid(1-42) (A beta) in a small group of neurons in the adult fly and performed extensive time course analysis of the function and structure of both axon and presynaptic terminals at the identified single-neuron level. A beta accumulated intracellularly and induced a range of age-dependent changes, including depletion of presynaptic mitochondria, slowdown of bi-directional transports of axonal mitochondria, decreased synaptic vesicles, increased large vacuoles, and elevated synaptic fatigue. These structural and functional synaptic changes correlated with age-dependent deficit in motor behavior. All these alterations were accelerated in flies expressing the arctic form of A beta. The depletion of presynaptic mitochondria was the earliest detected phenotype and was not caused by the change in axonal transport of mitochondria. Moreover, axonal mitochondria exhibited a dramatic reduction in number but a significant increase in size in aged A beta-expressing flies, indicating a global depletion of mitochondria in the neuron and an impairment of mitochondria fission. These results suggest that A beta accumulation depletes presynaptic and axonal mitochondria, leading to other presynaptic deficits.