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Segal-Salto M, Hansson K, Sapir T, Kaplan A, Levy T, Schweizer M, Frotscher M, James P, Reiner O. Proteomics insights into infantile neuronal ceroid lipofuscinosis (CLN1) point to the involvement of cilia pathology in the disease. Hum Mol Genet 2017; 26:1678. [PMID: 28334871 DOI: 10.1093/hmg/ddx074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 02/20/2017] [Indexed: 01/23/2023] Open
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. Analysis of membrane proteins from brain enriched for acylated proteins from neonate Ppt1 knock out and control mice revealed a list of 88 proteins with differential expression levels. Amongst them, we identified Rab3IP, which regulates ciliogenesis in concert with Rab8 and Rab11. Immunostaining analysis revealed that PPT1 is localized in the cilia. Indeed, an unbiased proteomics analysis on isolated cilia revealed 660 proteins, which differed in their abundance levels between wild type and Ppt1 knock out. We demonstrate here that Rab3IP, Rab8 and Rab11 are palmitoylated, and that palmitoylation of Rab11 is required for correct intracellular localization. Cells and brain preparations from Ppt1-/- mice exhibited fewer cells with cilia and abnormally longer cilia, with both acetylated tubulin and Rab3IP wrongly distributed along the length of cilia. Most importantly, the analysis revealed a difference in the distribution and levels of the modified proteins in cilia in the retina of mutant mice versus the wildtype, which may be important in the early neurodegenerative phenotype. Overall, our results suggest a novel link between palmitoylated proteins, cilial organization and the pathophysiology of Neuronal Ceroid Lipofuscinosis.
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Affiliation(s)
- Michal Segal-Salto
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Karin Hansson
- Department of Immunotechnology, Lund University, Medicon Village, Lund, Sweden and BTK, Åbo Academy University, Turku, Finland
| | - Tamar Sapir
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Anna Kaplan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Talia Levy
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Michaela Schweizer
- Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Michael Frotscher
- Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Peter James
- Department of Immunotechnology, Lund University, Medicon Village, Lund, Sweden and BTK, Åbo Academy University, Turku, Finland
| | - Orly Reiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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Takao D, Dishinger JF, Kee HL, Pinskey JM, Allen BL, Verhey KJ. An assay for clogging the ciliary pore complex distinguishes mechanisms of cytosolic and membrane protein entry. Curr Biol 2014; 24:2288-94. [PMID: 25264252 DOI: 10.1016/j.cub.2014.08.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 07/08/2014] [Accepted: 08/07/2014] [Indexed: 01/25/2023]
Abstract
As a cellular organelle, the cilium contains a unique protein composition. Entry of both membrane and cytosolic components is tightly regulated by gating mechanisms at the cilium base; however, the mechanistic details of ciliary gating are largely unknown. We previously proposed that entry of cytosolic components is regulated by mechanisms similar to those of nuclear transport and is dependent on nucleoporins (NUPs), which comprise a ciliary pore complex (CPC). To investigate ciliary gating mechanisms, we developed a system to clog the pore by inhibiting NUP function via forced dimerization. We targeted NUP62, a component of the central channel of the nuclear pore complex (NPC), for forced dimerization by tagging it with the homodimerizing Fv domain. As proof of principle, we show that forced dimerization of NUP62-Fv attenuated (1) active transport of BSA into the nuclear compartment and (2) the kinesin-2 motor KIF17 into the ciliary compartment. Using the pore-clogging technique, we find that forced dimerization of NUP62 attenuated the gated entry of cytosolic proteins but did not affect entry of membrane proteins or diffusional entry of small cytosolic proteins. We propose a model in which active transport of cytosolic proteins into both nuclear and ciliary compartments requires functional NUPs of the central pore, whereas lateral entry of membrane proteins utilizes a different mechanism that is likely specific to each organelle's limiting membrane.
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Affiliation(s)
- Daisuke Takao
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - John F Dishinger
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - H Lynn Kee
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Justine M Pinskey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Ben L Allen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Kristen J Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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