Scyl1, mutated in a recessive form of spinocerebellar neurodegeneration, regulates COPI-mediated retrograde traffic.
Scy1-like 1 (Scyl1), a member of the Scy1-like family of catalytically inactive protein kinases, was recently identified as the gene product altered in muscle-deficient mice, which suffer from motor neuron degeneration and cerebellar atrophy. To determine the function of Scyl1, we have now used a mass spectrometry-based screen to search for Scyl1-binding partners and identified components of coatomer I (COPI) coats. The interaction was confirmed in pull-down assays, and Scyl1 co-immunoprecipitates with betaCOP from brain lysates. Interestingly, and unique for a non-transmembrane domain protein, Scyl1 binds COPI coats using a C-terminal RKLD-COO(-) sequence, similar to the KKXX-COO(-) COPI-binding motif found in transmembrane endoplasmic reticulum (ER) proteins. Scyl1 co-localizes with betaCOP and is localized, in an Arf1-independent manner, to the ER-Golgi intermediate compartment and the cis-Golgi, sites of COPI-mediated membrane budding. The localization and binding properties of Scyl1 strongly suggest a function in COPI transport, and inhibitory RNA-mediated knock down of the protein disrupts COPI-mediated retrograde traffic of the KDEL receptor to the ER without affecting anterograde traffic from the ER. Our data demonstrate a function for Scyl1 as an accessory factor in COPI trafficking and suggest for the first time that alterations in the COPI pathway result in neurodegenerative disease.
Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada.
Jonathon L
JL
Burman
Lyne
L
Bourbonniere
Jacynthe
J
Philie
Thomas
T
Stroh
Selma Y
SY
Dejgaard
John F
JF
Presley
Peter S
PS
McPherson
D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology; D020755:Coat Protein Complex I / Q000378:metabolism*; D005808:Genes, Recessive; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D013132:Spinocerebellar Degenerations / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D033942:Adaptor Proteins, Vesicular Transport; D020755:Coat Protein Complex I; C531983:Scyl1 protein, rat; D014157:Transcription Factors; D011494:Protein Kinases