ATXN3 and proteostasis deficiencies: To validate the use of FloIT as a tool to screen the effect of compounds on detergent-insoluble ataxin-3 protein species, we treated cells transiently transfected with EGFP ataxin-3 84Q for 24 h with 3-methyladenine (3MA), a known inhibitor of autophagy (Klionsky et al., 2021; Seglen and Gordon, 1982), and calpeptin, a compound known to induce autophagy and reduce proteinopathy in polyQ disease models (Watchon et al., 2017; Haacke et al., 2007; Menzies et al., 2015).