Identification of regulatory elements in the C‐terminus of the Protein Acyl Transferase, zDHHC9.

Mutations in zDHHC9, a Ras palmitoyltransferase, has been linked to X‐Linked Intellectual Disability (XLID). zDHHC9 catalyzes the palmitoylation of its substrates by a two‐step transferase reaction, the first being the autopalmitoylation of the enzyme with palmitoyl‐CoA serving a palmitoyl donor. The second step is the transfer for palmitate from zDHHC9 to its substrate. Several XLID mutations have been shown to be defective in autopalmitoylation or palmitoyl transfer. However, one mutation, R298*, causing a premature truncation of the C‐terminus of the protein. Interestingly, the zDHHC9(R298*) mutant protein is catalytically active, but exhibits a subcellular trafficking defect in neurons. This region of the protein is predicted to be intrinsically disordered. In this study, we test the hypothesis that there is a motif or motifs in the C‐terminal intrinsically disordered region that is required for subcellular location and substrate engagement by zDHHC9. This region includes a three cysteine cluster found in other members of the zDHHC family. Mutation of the three cysteine impairs location and is inactive in an orthotopic yeast zDHHC functional assay. We are testing whether one or more of these cysteines are palmitoylated. In addition, we are using BioID to identify proteins that interact with the zDHHC9 C‐terminus. We propose that identification of zDHHC9 interacting proteins will reveal how localization regulates palmitoyltransferase activity and contribute to our understanding of zDHHC9 dependent palmitoylation contributes to neuronal development and XLID.