How risk genes of late-onset Alzheimer’s disease contribute to the outset of lysosomal homeostasis impairment in neurons at early stages of the neuropathogenic cascade: the case of PLD3.

Phospholipase D3 (PLD3) is a brain-expressed protein of which the cellular functions remain to be elucidated. Nevertheless, PLD3 was identified in genetic studies as a risk factor for the development of late-onset Alzheimer’s disease, by far the most frequent form of dementia. PLD3 is localized in degradative compartments of neurons that are known to be malfunctioning in early disease stages and to be involved in the aggregation of toxic amyloid and the associated metabolic dysregulations. Hence, the question arises what functions PLD3 does exert in these organelles and how its failure results in lysosomal degradation and transport problems in neurons that end in neuronal cell death. We will investigate this using a nanotechnology approach based on the specific isolation of degradative organelles by magnetic nanoparticles (SPIONs), followed by high-resolution analysis of their protein and lipid composition. For this, new cell models are developed: neuroblastoma cells wherein PLD3 is knocked out and human neurons derived from patient fibroblasts, which harbour PLD3 nucleotide polymorphisms. This methodology will enable us to generate unbiased data on PLD3 functions in cellular transport mechanisms, to pinpoint those steps/mechanisms most affected in PLD3 risk carriers and indicate whether or not these dysfunctions are mutation-dependent. If successful, this strategy can be extended to other Alzheimer risk factors, underscoring the strong generic nature of the proposal.