ATM protein is located on presynaptic vesicles and its deficit leads to failures in synaptic plasticity

Ataxia-telangiectasia is a multi-systemic disorder that includes a devastating neurodegeneration phenotype. The ATM (ataxia-telangiectasia mutated) protein is well-known for its role in the DNA damage response. Yet ATM is also found in association with cytoplasmic vesicular structures - endosomes and lysosomes as well as neuronal synaptic vesicles. In keeping with this latter association, electrical stimulation of the Schaffer collateral pathway in hippocampal slices from ATM-deficient mice does not elicit normal long term potentiation (LTP). The current study was undertaken to assess the nature of this deficit. Theta burst-induced LTP was reduced in Atm-/- animals with the reduction most pronounced at burst stimuli that included six or greater trains. To assess whether the deficit was associated with a pre- or post-synaptic failure, we analyzed paired-pulse facilitation and found that it too was significantly reduced in Atm-/- mice. This indicates a deficit in presynaptic function. As further evidence that these synaptic effects of ATM deficiency were presynaptic, we used stochastic optical reconstruction microscopy (STORM). Three-dimensional reconstruction revealed that ATM is significantly more closely associated with Piccolo (a pre-synaptic marker) than with Homer1 (a post-synaptic marker). These results underline how, in addition to its nuclear functions, ATM plays an important functional role in the neuronal synapse where it participates in the regulation of presynaptic vesicle physiology.

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