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Proteomics insights into Infantile Neuronal Ceroid Lipofuscinosis (CLN1) point to the involvement of palmitoylation in the disease

ABSTRACT: Mutations in the depalmitoylation enzyme, palmitoyl protein thioesterase (PPT1), result in the early onset neurodegenerative disease known as Infantile Neuronal Ceroid Lipofuscinosis. Here, we provide proteomic evidence suggesting that PPT1 deficiency could be considered as a ciliopathy. An unbiased proteomic analysis of membranal brain proteins from neonate Ppt1 knock out and control mice revealed a list of 88 proteins with different expression levels. Among them, we identified Rab3IP, which is known to work in concert with Rab8 and Rab11 to regulated proper ciliogenesis. Surprisingly, PPT1 was observed to localize to cilia. Indeed, an unbiased proteomics analysis on isolated cilia revealed 660 proteins, which differed in their abundance between wild type and Ppt1 knock out. We demonstrate here that Rab3IP, Rab8 and Rab11 are palmitoylated proteins, and palmitoylation of Rab11 is required for proper intracellular localization. Most interestingly, cells and tissues from Ppt1-/- exhibited less ciliated cells and abnormally longer cilia with both acetylated tubulin and Rab3IP mis-distributed along the length of cilia. Overall, our results suggest a novel link between palmitoylated proteins, cilia organization and the pathophysiology of Neuronal Ceroid Lipofuscinosis.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Brain

DISEASE(S): Neuronal Ceroid Lipofuscinosis

SUBMITTER: Peter James

LAB HEAD: Peter James

PROVIDER: PXD001966 | Pride | 2021-12-14

REPOSITORIES: Pride

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Project description:Mutations in Ppt1, which is a depalmitoylation enzyme result in early onset neurodegeneration, therefore, we hypothesized that the protein content of brain membranes from mutant newborn mice will differ from those derived from wild-type. This unbiased analysis revealed that the majority of the differentially identified proteins are palmitoylated and their upstream pathway analysis point to neurodegenerative diseases. One of the differentially expressed proteins was Rab3IP, which is a direct downstream effector of Rab11 and affects the guanine nucleotide-exchange activity of Rab3IP toward Rab8. Rab3IP, Rab11 and Rab8 are known to be involved in ciliogenesis. Rab3IP distribution in cilia differed between the wild type and the mutant cells. Our analysis showed that these three proteins are palmitoylated. Site-directed mutagenesis of the palmitoylation sites of Rab11 affects its intracellular localization. Most importantly, in MEFs, neuroblasts, neurons and brain preparations, longer cilia were detected in Ppt1-/-. Collectively, our studies suggest that cilia abnormalities need to be considered as part of the pathophysiology of CLN1. Mutations in Ppt1, which is a depalmitoylation enzyme result in early onset neurodegeneration, therefore, we hypothesized that the protein content of brain membranes from mutant newborn mice will differ from those derived from wild-type. This unbiased analysis revealed that the majority of the differentially identified proteins are palmitoylated and their upstream pathway analysis point to neurodegenerative diseases. One of the differentially expressed proteins was Rab3IP, which is a direct downstream effector of Rab11 and affects the guanine nucleotide-exchange activity of Rab3IP toward Rab8. Rab3IP, Rab11 and Rab8 are known to be involved in ciliogenesis. Rab3IP distribution in cilia differed between the wild type and the mutant cells. Our analysis showed that these three proteins are palmitoylated. Site-directed mutagenesis of the palmitoylation sites of Rab11 affects its intracellular localization. Most importantly, in MEFs, neuroblasts, neurons and brain preparations, longer cilia were detected in Ppt1-/-. Collectively, our studies suggest that cilia abnormalities need to be considered as part of the pathophysiology of CLN1. Mutations in Ppt1 result in early onset neurodegeneration, therefore, we hypothesized that the levels of proteins extracted from purified brain membranes of newborn mice will differ. One of the main effects of palmitoylation is changing the hydrophobic index of proteins and thus affecting these proteins interactions with different membranal domains. Assuming that PPT1 substrates are over palmitoylated in Ppt1-/- brains it is possible that its localization to specific membranal domain is different than in the wild-type brains. We isolated Triton X-100 soluble membranes from three wild-type and three Ppt1-/- brains and identified the proteins by PalmPISC. Many of the identified proteins were found to be palmitoylated. A second feature, which was noted is that many of the differential proteins (62 out of 88, 70%) can be detected in the cilia proteome (http://v3.ciliaproteome.org/cgi-bin/index.php). This observation led to test whether ciliary proteins differ between wild-type and Ppt1-/-. Cilia were prepared from newborn dissociated brain cell cultures and analyzed by MS

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Proteomics insights into Infantile Neuronal Ceroid Lipofuscinosis (CLN1) point to the involvement of palmitoylation in the disease

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