The p75 neurotrophin receptor is localized to primary cilia in adult murine hippocampal dentate gyrus granule cells

The densely ciliated granule cell layer of the adult murine hippocampal dentate gyrus is one of two sites of adult neurogenesis. The granule cells have already been proven to localize their SSTR3 (somatostatin receptor 3) receptors to their so-called primary cilia. Here we show for the first time that 70–90% of these cells in 7–18 months-old wild-type and 3xTg-AD (Alzheimer disease transgenic) mice also load p75NTR receptors into the structures containing SSTR3, i.e., their primary cilia. On the other hand, p75NTR’s TrkA co-receptors were not localized to cilia but conventionally distributed throughout the cell surface. Significantly fewer cells (20–40%) in the hippocampal CA1 and CA3 regions and cerebral cortex have p75NTR containing cilia. While we don’t know what the impact of the cilial localization of p75NTR on dentate gyral adult neurogenesis and memory encoding might be, the cilia’s amyloid beta-activatable p75NTR receptors could be damaging or lethal to the hippocampal functioning of amyloid beta–accumulating Alzheimer brain.