Palmitoyl Acyltransferases Control the Membrane Localization of <scp>DNAJC5</scp> to Regulate Unconventional Protein Secretion

Misfolded proteins lacking signal sequence can be secreted into the extracellular space via an unconventional protein secretion (UcPS) process termed misfolding-associated protein secretion (MAPS), which involves HSP70 and a membrane-associated HSP70 co-chaperone named DNAJC5. Here, we show that DNAJC5 can be palmitoylated by several DHHC palmitoyl acyltransferases in human cells. Among them, DHHC11 has a modest activity toward DNAJC5, but its overexpression enriches DNAJC5 in a Golgi-associated compartment, which correlates with increased secretion. Mutagenesis studies show that a minimum DNAJC5 module (DC95) consisting of the palmitoyl acceptor-enriched cysteine string (CS) domain plus the C-terminal 62 residues and a short upstream segment is sufficient to drive palmitoylation, Golgi translocation and secretion. In contrast, removal of 5 residues from DC95 abolishes its palmitoylation, Golgi association and secretion. These findings suggest that the palmitoylation sites of DNAJC5 act with flanking sequences to control its subcellular localization and UcPS function.