Defining the mechanisms of action of the anti-psychotic drug (APD), clozapine is of great importance, as clozapine is more effective and has therapeutic benefits in a broader range of psychiatric disorders than other APDs. Its range of actions have not been fully characterized. Exposure to APDs early in development causes dose-dependent developmental delay and lethality in C. elegans. A previous genome-wide RNAi screen for suppressors of clozapine-induced developmental delay and lethality revealed 40 candidate genes, including
sms-1, which encodes a sphingomyelin synthase. One
sms-1 isoform is expressed in the C. elegans pharynx, and its transgene rescues the
sms-1 mutant phenotype. We examined pharyngeal pumping and observed that clozapine-induced inhibition of pharyngeal pumping requires
sms-1, a finding that may explain the role of the gene in mediating clozapine-induced developmental delay/lethality. By analyzing multiple enzymes involved in sphingolipid metabolism, and by observing the effect of addition of various lipids directly to the worms, we suggest that glucosylceramide may be a key mediator of the effects of clozapine. We further observed that clozapine clears protein aggregates, such as alpha-synuclein, PolyQ protein and alpha-1-antitrypsin mutant protein (ATZ). In addition, it enhances ATG8/LC3. We conclude that clozapine appears to affect the development and induce lethality of worms in part through modulating glucosylceramide. We discuss the possible connections among glucosylceramide, protein aggregate clearance and autophagy. Interactions, including mechanistic pathways involving these elements, may underlie some of the clinical effects of clozapine.Neuropsychopharmacology accepted article preview online, 06 October 2016. doi:10.1038/npp.2016.230.