title: Spatial regulation of Raf kinase signaling by RKTG.
abstract: Subcellular compartmentalization has become an important theme in cell signaling such as spatial regulation of Ras by RasGRP1 and MEK/ERK by Sef. Here, we report spatial regulation of Raf kinase by RKTG (Raf kinase trapping to Golgi). RKTG is a seven-transmembrane protein localized at the Golgi apparatus. RKTG expression inhibits EGF-stimulated ERK and RSK phosphorylation, blocks NGF-mediated PC12 cell differentiation, and antagonizes Ras- and Raf-1-stimulated Elk-1 transactivation. Through interaction with Raf-1, RKTG changes the localization of Raf-1 from cytoplasm to the Golgi apparatus, blocks EGF-stimulated Raf-1 membrane translocation, and reduces the interaction of Raf-1 with Ras and MEK1. In RKTG-null mice, the basal ERK phosphorylation level is increased in the brain and liver. In RKTG-deleted mouse embryonic fibroblasts, EGF-induced ERK phosphorylation is enhanced. Collectively, our results reveal a paradigm of spatial regulation of Raf kinase by RKTG via sequestrating Raf-1 to the Golgi apparatus and thereby inhibiting the ERK signaling pathway.
authors.affiliation: Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Feng
authors.forename: Xiaoduo
authors.initials: X
authors.lastname: Xie
authors.forename: Qiurong
authors.initials: Q
authors.lastname: Ding
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Luo
authors.forename: Jing
authors.initials: J
authors.lastname: He
authors.forename: Fengjuan
authors.initials: F
authors.lastname: Fan
authors.forename: Weizhong
authors.initials: W
authors.lastname: Liu
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D017353:Gene Deletion; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C523677:RKTG protein, mouse; D048490:raf Kinases