Premium
Mutations in the zDHHC9 protein palmitoyltransferase result in X‐Linked Intellectual Disability (XLID) by distinct mechanisms
Author(s) -
Ramadan Ahmed S,
Kirouac Lisa S,
Sales Conniff Amanda E,
Serraneou Karisa,
Dzaferi Medina,
Schlosser Sydni S,
Pendleton Laura S,
Deschenes Robert J
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.632.10
Subject(s) - palmitoylation , biology , mutation , missense mutation , microbiology and biotechnology , golgi apparatus , gene , nonsense mutation , hek 293 cells , phosphorylation , genetics , biochemistry , enzyme , cell , cysteine
The zDHHC9 gene, which encodes a Ras palmitoyltransferase is highly expressed in the brain and the protein is enriched in the hippocampus, a region known to be involved with learning and memory. Loss of function mutations in the zDHHC9 result in lead X‐Linked Intellectual Disabilities (XLID). Analysis of the disease causing mutations has begun to provide insights into the molecular mechanisms underlining the neuronal function of protein palmitoylation. Previously we published that two missense mutations in zDHHC9 (P150S and R148W) result in a decrease in enzyme autopalmitoylation, the first of the two step reaction mechanism (JBC 289:18582 (2014)). Here we show that a nonsense mutation, R298* that truncates the C‐terminal 66‐amino acids of zDHHC9, results in an enzymatically active, but trafficking defective protein. Specifically, wild type zDHHC9 is localized in the Golgi and traffics via a microtubules based mechanism to distal sites of the neuron. In contrast, the truncated R298* protein is restricted to the Golgi. This suggests that subcellular localization is required to engage specific protein substrates involved with neuronal function. Since it is known that zDHHC9 palmitoylates Ras proteins, we investigated whether the loss of zDHHC9 function changes Ras dependent signaling. Wild type HAP1 cells were compared with HAP1 cells in which the zDHHC9 gene has been deleted. In cells lacking zDHHC9 there was a decrease in S6K and AKT1 phosphorylation, consistent with a reduction in Ras signaling. We are in the process of analyzing additional disease mutations of zDHHC9 using cell lines, rat hippocampal neurons and a yeast palmitoylation functional assay. In addition, Acyl‐RAC and ABE methods, coupled with mass spectrometry are being used to identify zDHHC9 substrates in neurons. These studies will provide insight into the role of palmitoylation in the pathophysiology of XLID. Support or Funding Information This study was supported by a grant from NIH R21NS090160 to RJD. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .