title: The ubiquitin-like protein LC3 regulates the Rho-GEF activity of AKAP-Lbc.
abstract: AKAP-Lbc is a member of the A-kinase anchoring protein (AKAP) family that has been recently associated with the development of pathologies, such as cardiac hypertrophy and cancer. We have previously demonstrated that, at the molecular level, AKAP-Lbc functions as a guanine nucleotide exchange factor (GEF) that promotes the specific activation of RhoA. In the present study, we identified the ubiquitin-like protein LC3 as a novel regulatory protein interacting with AKAP-Lbc. Mutagenesis studies revealed that LC3, through its NH(2)-terminal alpha-helical domain, interacts with two binding sites located within the NH(2)-terminal regulatory region of AKAP-Lbc. Interestingly, LC3 overexpression strongly reduced the ability of AKAP-Lbc to interact with RhoA, profoundly impairing the Rho-GEF activity of the anchoring protein and, as a consequence, its ability to promote cytoskeletal rearrangements associated with the formation of actin stress fibers. Moreover, AKAP-Lbc mutants that fail to interact with LC3 show a higher basal Rho-GEF activity as compared with the wild type protein and become refractory to the inhibitory effect of LC3. This suggests that LC3 binding maintains AKAP-Lbc in an inactive state that displays a reduced ability to promote downstream signaling. Collectively, these findings provide evidence for a previously uncharacterized role of LC3 in the regulation of Rho signaling and in the reorganization of the actin cytoskeleton.
authors.affiliation: Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Rue du Bugnon 27, Lausanne 1005, Switzerland.
authors.forename: Laurent
authors.initials: L
authors.lastname: Baisamy
authors.affiliation: Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Rue du Bugnon 27, Lausanne 1005, Switzerland.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Cavin
authors.affiliation: Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Rue du Bugnon 27, Lausanne 1005, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Jurisch
authors.affiliation: Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Rue du Bugnon 27, Lausanne 1005, Switzerland. Electronic address: Dario.diviani@unil.ch.
authors.forename: Dario
authors.initials: D
authors.lastname: Diviani
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D008958:Models, Molecular; D041681:NIH 3T3 Cells; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000502:physiology; D020798:Two-Hybrid System Techniques
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D020662:Guanine Nucleotide Exchange Factors; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D015778:Minor Histocompatibility Antigens; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors
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