Protein S-palmitoylation is a reversible post-translational modification mediated by palmitoyl acyltransferase enzymes, a group of Zn²⁺-finger DHHC-domain-containing proteins (ZDHHC). Here, for the first time, we show that Zdhhc13 plays a key role in anxiety-related behaviors and motor function, as well as brain bioenergetics, in a mouse model (luc) carrying a spontaneous Zdhhc13 recessive mutation. At 3 m of age, mutant mice displayed increased sensorimotor gating, anxiety, hypoactivity, and decreased motor coordination, compared to littermate controls. Loss of Zdhhc13 in cortex and cerebellum from 3- and 24 m old hetero- and homozygous male mutant mice resulted in lower levels of Drp1 S-palmitoylation accompanied by altered mitochondrial dynamics, increased glycolysis, glutaminolysis and lactic acidosis, and neurotransmitter imbalances. Employing in vivo and in vitro models, we identified that Zdhhc13-dependent Drp1 S-palmitoylation, which acting alone or in concert, enables the normal occurrence of the fission-fusion process. In vitro and in vivo direct Zdhhc13-Drp1 protein interaction was observed, confirming Drp1 as a substrate of Zdhhc13. Abnormal fission-fusion processes result in disrupted mitochondria morphology and distribution affecting not only mitochondrial ATP output but neurotransmission and integrity of synaptic structures in the brain, setting the basis for the behavioral abnormalities described in the Zdhhc13-deficient mice.

Human protein arginine methyltransferase (PRMT) 9 symmetrically dimethylates arginine residues on splicing factor SF3B2 (SAP145) and has been functionally linked to the regulation of alternative splicing of pre-mRNA. Site-directed mutagenesis studies on this enzyme and its substrate had revealed essential unique residues in the double E loop and the importance of the C-terminal duplicated methyltransferase domain. In contrast to what had been observed with other PRMTs and their physiological substrates, a peptide containing the methylatable Arg-508 of SF3B2 was not recognized by PRMT9 in vitro. Although amino acid substitutions of residues surrounding Arg-508 had no great effect on PRMT9 recognition of SF3B2, moving the arginine residue within this sequence abolished methylation. PRMT9 and PRMT5 are the only known mammalian enzymes capable of forming symmetric dimethylarginine (SDMA) residues as type II PRMTs. We demonstrate here that the specificity of these enzymes for their substrates is distinct and not redundant. The loss of PRMT5 activity in mouse embryo fibroblasts results in almost complete loss of SDMA, suggesting that PRMT5 is the primary SDMA-forming enzyme in these cells. PRMT9, with its duplicated methyltransferase domain and conserved sequence in the double E loop, appears to have a unique structure and specificity among PRMTs for methylating SF3B2 and potentially other polypeptides.

Here we describe a spontaneous mutation in the Zdhhc13 (zinc finger, DHHC domain containing 13) gene (also called Hip14l), one of 24 genes encoding palmitoyl acyltransferase (PAT) enzymes in the mouse. This mutation (Zdhhc13luc) was identified as a nonsense base substitution, which results in a premature stop codon that generates a truncated form of the ZDHHC13 protein, representing a potential loss-of-function allele. Homozygous Zdhhc13luc/Zdhhc13luc mice developed generalized hypotrichosis, associated with abnormal hair cycle, epidermal and sebaceous gland hyperplasia, hyperkeratosis, and increased epidermal thickness. Increased keratinocyte proliferation and accelerated transit from basal to more differentiated layers were observed in mutant compared with wild-type (WT) epidermis in untreated skin and after short-term 12-O-tetradecanoyl-phorbol-13-acetate treatment and acute UVB exposure. Interestingly, this epidermal phenotype was associated with constitutive activation of NF-κB (RelA) and increased neutrophil recruitment and elastase activity. Furthermore, tumor multiplicity and malignant progression of papillomas after chemical skin carcinogenesis were significantly higher in mutant mice than WT littermates. To our knowledge, this is the first report of a protective role for PAT in skin carcinogenesis.