Live Cell Fluorescence Imaging Shows Neurotransmitter Activation Promotes Aggregation of the Intracellular Domain of Amyloid Precursor Protein.

Amyloid precursor protein (APP) is a major contributor to the pathology of Alzheimer's and other neurodegenerative diseases through the accumulation of extracellular plaques. Here, we have studied changes in APP translation and aggregation of the APP intracellular domain when the Gαq/PLCβ signaling system is activated by neurotransmitters. Using RT-PCR and a molecular beacon that follows APP mRNA in live cells, we find that Gαq activation sequesters APP mRNA similar to the stress granule response found in heat shock and hypo-osmotic shock thereby shutting down the production of APP. Following the intracellular domain of eGFP-APP, we find that Gαq stimulation increases aggregation as followed by number and brightness (N&B) analysis of single molecule fluorescence time series. Additionally, we show that APP aggregation is affected by changes in the levels of PLCβ1 and its cytosolic binding partners. Our studies show the neurotransmitter activation of Gαq/PLCβ reduces translation of APP and increases aggregation of its intracellular domain. These studies better establish a link between APP production and complexation and Gαq stimulation.