title: ERK1/2 associates with the c-Met-binding domain of growth factor receptor-bound protein 2 (Grb2)-associated binder-1 (Gab1): role in ERK1/2 and early growth response factor-1 (Egr-1) nuclear accumulation.
abstract: Endothelial cell (EC) migration contributes to reendothelialization after angioplasty or rupture of atherosclerotic plaques. Extracellular signal-regulated kinase (ERK)1/2 translocates to the nucleus and activates transcription factors such as Ets-like transcription factor-1 and early growth response factor-1 (Egr-1) during reendothelialization. Because ERK1/2 does not possess a nuclear localization signal (NLS), its mechanism of translocation and accumulation in the nucleus remains unclear. Because Gab1 has a putative NLS in its N-terminal region, and Gab1 associates with phosphorylated ERK1/2, we hypothesized that Gab1 participates in ERK1/2 and Egr-1 nuclear accumulation. Using regenerating EC as a model system, we found that endogenous growth factor receptor-bound protein 2-associated binder-1 (Gab1) translocates into the nucleus in migrating EC. Wild-type red fluorescent protein-tagged Gab1 could be observed in both nucleus and cytoplasm, whereas the putative NLS deletion mutant (deltaNLS-Gab1) specifically localized in the cytoplasm. In addition, reduction of Gab1 expression by antisense Gab1 oligos or overexpression of deltaNLS-Gab1 inhibited serum-induced ERK1/2 and Egr-1 nuclear accumulation, suggesting a functional role for the NLS of Gab1 and a role for Gab1-ERK1/2 interactions in ERK1/2-Egr-1 nuclear accumulation. To investigate whether Gab1-ERK1/2 interaction is critical for ERK1/2 and Egr-1 nuclear accumulation, we created a dominant-negative Gab1 construct that consisted of the c-Met binding domain (amino acids 442-536) of Gab1. We found that overexpression of the c-Met binding domain of Gab1 disrupted serum-induced Gab1-ERK1 interaction and inhibited ERK1 and Egr-1 nuclear accumulation. These data suggest that Gab1-ERK1/2 binding and their nuclear translocation play a crucial role in Egr-1 nuclear accumulation.
authors.affiliation: Center for Cardiovascular Research, University of Rochester, Rochester, New York 14642, USA.
authors.forename: Masaki
authors.initials: M
authors.lastname: Osawa
authors.forename: Seigo
authors.initials: S
authors.lastname: Itoh
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Ohta
authors.forename: Qunhua
authors.initials: Q
authors.lastname: Huang
authors.forename: Bradford C
authors.initials: BC
authors.lastname: Berk
authors.forename: Nicole-Lerner
authors.initials: NL
authors.lastname: Marmarosh
authors.forename: Wenyi
authors.initials: W
authors.lastname: Che
authors.forename: Bo
authors.initials: B
authors.lastname: Ding
authors.forename: Chen
authors.initials: C
authors.lastname: Yan
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Abe
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D016466:CHO Cells; D002417:Cattle; D002478:Cells, Cultured; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019913:Nuclear Localization Signals; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D019913:Nuclear Localization Signals; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D019859:Proto-Oncogene Proteins c-met; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases