Effects of diet on synaptic vesicle release in dynactin complex mutants: a mechanism for improved vitality during motor disease

Abstract

Summary Synaptic dysfunction is considered the primary substrate for the functional declines observed within the nervous system during age-related neurodegenerative disease. Dietary restriction (DR), which extends lifespan in numerous species, has been shown to have beneficial effects on many neurodegenerative disease models. Existing data sets suggest that the effects of DR during disease include the amelioration of synaptic dysfunction but evidence of the beneficial effects of diet on the synapse is lacking. Dynactin mutant flies have significant increases in mortality rates and exhibit progressive loss of motor function. Using a novel fly motor disease model, we demonstrate that mutant flies raised on a low calorie diet have enhanced motor function and improved survival compared to flies on a high calorie diet. Neurodegeneration in this model is characterized by an early impairment of neurotransmission that precedes the deterioration of neuromuscular junction (NMJ) morphology. In mutant flies, low calorie diet increases neurotransmission, but has little effect on morphology, supporting the hypothesis that enhanced neurotransmission contributes to the effects of diet on motor function. Importantly, the effects of diet on the synapse are not due to the reduction of mutant pathologies, but by the increased release of synaptic vesicles during activity. The generality of this effect is demonstrated by the observation that diet can also increase synaptic vesicle release at wild type NMJs. These studies reveal a novel presynaptic mechanism of diet that may contribute to the improved vigor observed in mutant flies raised on low calorie diet.

Extension of Health Span and Life Span in Drosophila by S107 Requires the calstabin Homologue FK506-BP2

“…To investigate this possibility, we analyzed synaptic transmission at the CM9 NMJ from 14-and 42-day-old wild type animals treated with S107 for 7 days. This NMJ is located on the CM9 muscle group of the proximal proboscis and is known to participate in proboscis extension (35,37). We observe no significant difference in the amplitude or shape of miniature end plate junctional potentials (mEJPs) between animals treated with vehicle and S107, demonstrating no change in the sensitivity of muscle to the excitable effects of neurotransmitter (Fig.…”

“…To investigate the effects of age on muscle function in Drosophila, we utilized a simple motor reflex in flies known as the proboscis extension reflex (PER) (35). The activation of the muscles controlling proboscis is motor neuron-dependent and utilizes a classic excitation:contraction coupling mechanism similar to mammalian skeletal muscles.…”

“…Proboscis Extension Reflex-Virgin flies of the appropriate age and genotypes were starved and deprived of water for 4 -6 h prior to PER analysis as previously described (35). Briefly, digital videos of individual PERs were captured at 9.2 Hz for at least 2 min using Slidebook software (Intelligent Imaging Innovations, Denver, CO).…”

“…CM9 Microscopy-CM9 muscles from 7-day-old female flies of indicated genotypes were processed for immunofluorescent microscopy using the primary antibody to Discs-large (1:500; Developmental Studies Hybridoma Bank) as previously described (35). CM9 muscle fibers were manually counted.…”

Dynein Interacts with the Neural Cell Adhesion Molecule (NCAM180) to Tether Dynamic Microtubules and Maintain Synaptic Density in Cortical Neurons

“…Also consistent with a role for dynein-dynactin in maintaining the stability of the NMJ, analysis of a transgenic mouse model expressing the G59S mutation in dynactin causative for human motor neuron disease (HMN7B) has shown significant synaptic destabilization in the absence of marked defects in axonal transport (52). Of note, the long term potentiation impairment observed in NCAM-deficient mice shows a pronounced age-dependent decline, whereas dynactin mutant (Glued) flies exhibit both morphological and functional deficits that increase with age (53).…”