title: A newly identified myomegalin isoform functions in Golgi microtubule organization and ER-Golgi transport.
abstract: The Golgi of mammalian cells is known to be a major microtubule-organizing site that requires microtubules for its organization and protein trafficking. However, the mechanisms underlying the microtubule organization of the Golgi remain obscure. We used immunoprecipitation coupled with mass spectrometry to identify a widely expressed isoform of the poorly characterized muscle protein myomegalin. This newly identified isoform, myomegalin variant 8 (MMG8), localized predominantly to cis-Golgi networks by interacting with AKAP450 (also known as AKAP9), and this interaction with AKAP450 was required for the stability of both proteins. Disrupting MMG8 expression affected endoplasmic reticulum (ER)-to-Golgi trafficking and caused Golgi fragmentation. Furthermore, MMG8 associated with γ-tubulin complexes and with the microtubule plus-end tracking protein EB1 (also known as MAPRE1), and was required for the Golgi localization of these two molecules. On the Golgi, γ-tubulin complexes mediated microtubule nucleation, whereas EB1 functioned in ER-to-Golgi trafficking. These results indicate that MMG8 participates in Golgi microtubule organization and thereby plays a crucial role in the organization and function of the Golgi.
authors.affiliation: Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China qirz@ust.hk.
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Qi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D003598:Cytoskeletal Proteins; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008870:Microtubules / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D020033:Protein Isoforms
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D009124:Muscle Proteins; D009687:Nuclear Proteins; C432971:PDE4DIP protein, human; D020033:Protein Isoforms
keywords: Golgi; Microtubule; Myomegalin; Protein trafficking