A NOVEL SCREENING SYSTEM TO IDENTIFY SMALL-MOLECULE INHIBITORS OF S-ACYLTRANSFERASES

CORONEL, CONSUELO; GIOLITO, MARIA LUZ; VALDEZ TAUBAS, JAVIER

Congreso; SAIB; 2019

Protein S-acylation or palmitoylation is a post-translational modification (PTM) that consists of the addition of long-chain fatty acids on cysteineresidues through a thioester bond. The labile nature of this bond makes this PTM the only lipid modification that is reversible and, therefore, withregulatory capabilities. Palmitoylation has multiple roles in many cellular processes, including signal transduction, protein traffic, and even geneexpression. This modification is highly prevalent and more than 10% of the human proteome is thought to be palmitoylated. Additionally, there isgrowing evidence that palmitoylation is closely linked to human health. For example, its misregulation has been associated with many types ofcancers and disorders of the nervous system, and many viral and bacterial pathogens require palmitoylation by the host machinery to thrive, makingthe enzymes responsible for this modification attractive drug targets. Palmitoylation is catalyzed by a family of palmitoyltransferases (PATs) orzDHHC proteins, which are polytopic membrane proteins characterized by the presence of a conserved DHHC-Cysteine Rich domain. There are7 members of this family in yeast and 23 in humans. Despite the importance of palmitoylation, no specific inhibitors of mammalian DHHC proteinsare currently available. There is a great need to develop such inhibitors to aid in the study of this modification and to test their possible therapeuticimplications. The aim of this work is to develop an in vivo screening system to identify putative small-molecule inhibitors for PATs. We describethe creation of yeast strains that enable us to positively select the cells in which palmitoylation by an individual PAT is inhibited. This system isbased on a reporter gene (HIS3) that responds to a transcription factor fused to a palmitoylation substrate. We show that the system works well forthe endogenous yeast PAT Akr1 and it can be adapted for the isolation of inhibitors of heterologous PATs, both from mammalian and parasiteorigins, such as human DHHC20, mouse DHHC21, and Giardia lamblia GL50803_6733. We are currently screening a 10000 compound library(3D Biodiversity by ChemDiv) and have several candidate molecules for further validation.