ARF6-mediated endocytosis: the missing link to the gamma-secretase independent role of presenilin 1 in neuronal membrane trafficking.

Next to its catalytic role in gamma-secretase complex, presenilin 1 (PSEN1) contributes to calcium homeostasis, apoptosis and endosomal trafficking. For instance, in PSEN1-/- hippocampal neurons, the adhesion molecule ICAM-5 accumulates in degradative organelles, implying endosomal sorting role for PSEN1. To further corroborate this finding we aim to identify and characterize the endocytic route affected in PSEN1-/- neurons. Preliminary findings suggest ARF - a small GTPase regulating macropinocytosis and actin remodeling - to be intimately related to ICAM-5 sorting dynamics. Hence we postulate a modulatory role of PSEN1 in ARF6-dependent ICAM-5 trafficking as our working hypothesis. This will be addressed by co-localization studies and live imaging of tagged proteins in combination with ARF6 transport blocking mutants in primary neurons. Furthermore, we will use agonist- or growth factor-induced stimulation of the ARF6 route to trigger or modulate ICAM-5 internalization. This knowledge will allow us to develop bioconjugated superparamagnetic nanoparticles to target and load ICAM-5/ARF6-positive endosomal compartments. Subcellular proteomics of these magnetically isolated organelles will hence generate their full protein inventories. Exploring endocytic deficiencies in PSEN1-/- neurons will identify key regulators in ARF6-mediated endosomal sorting, but may also provide novel early biomarkers as endosomal/lysosomal abnormalities are amongst the earliest neuropathologic features observed in sporadic Alzheimer's disease.

Keywords:Endosome, Hippocampal neuron, Presenilin

Disciplines:Systems biology, Medical biochemistry and metabolism, Biochemistry and metabolism, Microbiology