Real-time Nanoscale Organization of Amyloid Precursor Protein

Despite an intuitive understanding of the role of APP in health and disease, there exist few attempts to dissect its molecular localization at excitatory synapses. Though the biochemistry involved in the enzymatic processing of APP is well understood, there is a void in understanding the nonuniformity of the product formation in vivo. Here, we employed multiple paradigms of single molecule and ensemble based nanoscopic imaging to reveal that APP molecules are organized into regulatory nanodomains that are differentially compartmentalized in functional zones of an excitatory synapse. Furthermore, with the aid of high density single particle tracking, we show that lateral diffusion of APP in live cells dictate an equilibrium between these nanodomains and its nano-environment, which is affected in a detrimental variant of APP. Additionally, we incorporate this spatio-temporal detail ‘in silico’ to generate realistic nanoscale topography of APP in dendrites and synapses. This approach uncovers a nanoscale heterogeneity in the molecular organization of APP, depicting a locus for differential APP processing. This holistic paradigm, to decipher the real-time heterogeneity of the substrate molecules in nanoscale, could enable us to better evaluate the molecular constraints overcoming the ensemble approaches used traditionally to understand the kinetics of product formation.