Characterizing Dynamic Protein Interactions That Mediate mTOR Signaling in Shank3-deficient Neurons during Homeostatic Scaling

Abstract

The mTOR signaling cascade is a central signaling pathway that has been implicated in autism spectrum disorder (ASD). We have developed a Quantitative Multiplex Immunoprecipitation (QMI) panel to analyze changes in the mTOR protein interaction network (PIN). We observed extensive PIN one hour after the addition of fresh media despite phosphorylation changes occurring after five minutes. Various mTOR/ERK inhibitors acted on subsets of the PIN, referred to as modules, that responded differently to each inhibitor. Homeostatic scaling, induced by TTX or BIC treatment in cultured neurons, caused dissociations in different combinations of modules depending on scaling direction. In Shank3B-/- neurons, the scaling-responsive modules were pre-active at baseline and their response range was warped during scaling. Shank3B-/- neurons also produced an exaggerated response to treatment with the mTOR inhibitor Rapalink-1. These data provide the basis for understanding the relationship between mTOR signaling, synaptic scaling, and autism spectrum disorder.