title: Perturbations in actin dynamics reconfigure protein complexes that modulate GCN2 activity and promote an eIF2 response.
abstract: Genetic and pharmacological interventions in yeast and mammalian cells have suggested a cross-talk between the actin cytoskeleton and protein synthesis. Regulation of the activity of the translation initiation factor 2 (eIF2) is a paramount mechanism for cells to rapidly adjust the rate of protein synthesis and to trigger reprogramming of gene expression in response to internal and external cues. Here, we show that disruption of F-actin in mammalian cells inhibits translation in a GCN2-dependent manner, correlating with increased levels of uncharged tRNA. GCN2 activation increased phosphorylation of its substrate eIF2α and the induction of the integrated stress response master regulator, ATF4. GCN2 activation by latrunculin-B is dependent on GCN1 and inhibited by IMPACT. Our data suggest that GCN2 occurs in two different complexes, GCN2-eEF1A and GCN2-GCN1. Depolymerization of F-actin shifts GCN2 to favor the complex with GCN1, concomitant with GCN1 being released from its binding to IMPACT, which is sequestered by G-actin. These events might further contribute to GCN2 activation. Our findings indicate that GCN2 is an important sensor of the state of the actin cytoskeleton.
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo 04023-062, Brazil.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Silva
authors.affiliation: Institute of Natural and Mathematical Sciences, Massey University, Auckland 0745, New Zealand.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Sattlegger
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo 04023-062, Brazil bacastilho@unifesp.br.
authors.forename: Beatriz A
authors.identifier: 0000-0003-4509-5237
authors.initials: BA
authors.lastname: Castilho
mesh_terms: D000199:Actins / Q000378:metabolism*; D051701:Activating Transcription Factor 4; D049148:Aminoacylation; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D010766:Phosphorylation; D058105:Polymerization; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D051742:Transcription Factor CHOP / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000199:Actins; C081452:Atf4 protein, mouse; D002352:Carrier Proteins; D015852:Eukaryotic Initiation Factor-2; C504444:GCN1 protein, mouse; C107747:Impact protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D011506:Proteins; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP; D012343:RNA, Transfer; C070634:Eif2ak4 protein, mouse; D017346:Protein Serine-Threonine Kinases
keywords: Actin; EEF1A; GCN1; GCN2; IMPACT; Translation initiation