title: The Ubiquitin Ligase CBLC Maintains the Network Organization of the Golgi Apparatus.
abstract: The Golgi apparatus plays a pivotal role in the sorting and post-translational modifications of secreted and membrane proteins. In mammalian cells, the Golgi is organized in stacks of cisternae linked together to form a network with a ribbon shape. Regulation of Golgi ribbon formation is poorly understood. Here we find in an image-based RNAi screen that depletion of the ubiquitin-ligase CBLC induces Golgi fragmentation. Depletions of the close homologues CBL and CBLB do not induce any visible defects. In CBLC-depleted cells, Golgi stacks appear relatively unperturbed at both the light and electron microscopy levels, suggesting that CBLC controls mostly network organization. CBLC partially localizes on Golgi membranes and this localization is enhanced after activation of the SRC kinase. Inhibition of SRC reverts CBLC depletion effects, suggesting interplay between the two. CBLC's regulation of Golgi network requires its ubiquitin ligase activity. However, SRC levels are not significantly affected by CBLC, and CBLC knockdown does not phenocopy SRC activation, suggesting that CBLC's action at the Golgi is not direct downregulation of SRC. Altogether, our results demonstrate a role of CBLC in regulating Golgi ribbon by antagonizing the SRC tyrosine kinase.
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore; Department of Biochemistry, National University of Singapore, Singapore, Singapore.
authors.forename: Wan Yin
authors.initials: WY
authors.lastname: Lee
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore.
authors.forename: Germaine
authors.initials: G
authors.lastname: Goh
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore; Department of Biochemistry, National University of Singapore, Singapore, Singapore.
authors.forename: Joanne
authors.initials: J
authors.lastname: Chia
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore; Institute of Medical Biology, Singapore, Singapore; IMB-IMCB Joint Electron Microscopy Suite, Singapore, Singapore.
authors.forename: Adrian
authors.initials: A
authors.lastname: Boey
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore; Institute of Medical Biology, Singapore, Singapore; IMB-IMCB Joint Electron Microscopy Suite, Singapore, Singapore.
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Gunko
authors.affiliation: Institute of Molecular and Cell Biology, Singapore, Singapore; Department of Biochemistry, National University of Singapore, Singapore, Singapore.
authors.forename: Frederic
authors.initials: F
authors.lastname: Bard
mesh_terms: D045744:Cell Line, Tumor; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009154:Mutation; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics* / Q000378:metabolism*; D034622:RNA Interference; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism; D021601:trans-Golgi Network / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D049452:Green Fluorescent Proteins; D050721:Proto-Oncogene Proteins c-cbl; D019061:src-Family Kinases