title: The G1 Cyclin-dependent Kinase CRK1 in Trypanosoma brucei Regulates Anterograde Protein Transport by Phosphorylating the COPII Subunit Sec31.
abstract: Transport of secretory proteins from the endoplasmic reticulum to the Golgi is mediated by the coat protein II (COPII) complex comprising a Sec23-Sec24 heterodimer and a Sec13-Sec31 heterotetramer. The mechanisms underlying COPII-mediated protein trafficking have been well defined, but the extent of regulation of this secretory machinery by cellular signaling pathways remains poorly understood. Here, we report that CRK1, a G1 cyclin-dependent kinase in Trypanosoma brucei, regulates anterograde protein trafficking by phosphorylating Sec31. Depletion of CRK1 abolished anterograde transport of the secretory protein and disrupted the localization of multiple Golgi proteins, reminiscent of Sec31 depletion. CRK1 phosphorylates Sec31 at multiple serine/threonine sites, and mutation of these phosphosites to alanine recapitulates the protein trafficking defects caused by Sec31 depletion. Mutation of these CRK1 phosphosites to aspartate restored Sec31 function. Taken together, these results uncover a novel function of CRK1 in anterograde protein trafficking and elucidate the mechanistic role of CRK1 in protein trafficking through regulation of the COPII subunit Sec31.
authors.affiliation: From the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030 and.
authors.forename: Huiqing
authors.initials: H
authors.lastname: Hu
authors.affiliation: the Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California 94158.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Gourguechon
authors.affiliation: the Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California 94158.
authors.forename: Ching C
authors.initials: CC
authors.lastname: Wang
authors.affiliation: From the Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030 and ziyin.li@uth.tmc.edu.
authors.forename: Ziyin
authors.initials: Z
authors.lastname: Li
mesh_terms: D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015800:Protozoan Proteins; D033921:Vesicular Transport Proteins; D016203:CDC2 Protein Kinase; C095740:crk1 protein,Trypanosoma brucei
keywords: COPII; Trypanosoma brucei; chemical biology; cyclin; cyclin-dependent kinase (CDK); trafficking