title: Direct interaction of insulin-like growth factor-1 receptor with leukemia-associated RhoGEF.
abstract: Insulin-like growth factor (IGF)-1 plays crucial roles in growth control and rearrangements of the cytoskeleton. IGF-1 binds to the IGF-1 receptor and thereby induces the autophosphorylation of this receptor at its tyrosine residues. The phosphorylation of the IGF-1 receptor is thought to initiate a cascade of events. Although various signaling molecules have been identified, they appear to interact with the tyrosine-phosphorylated IGF-1 receptor. Here, we identified leukemia-associated Rho guanine nucleotide exchange factor (GEF) (LARG), which contains the PSD-95/Dlg/ZO-1 (PDZ), regulator of G protein signaling (RGS), Dbl homology, and pleckstrin homology domains, as a nonphosphorylated IGF-1 receptor-interacting molecule. LARG formed a complex with the IGF-1 receptor in vivo, and the PDZ domain of LARG interacted directly with the COOH-terminal domain of IGF-1 receptor in vitro. LARG had an exchange activity for Rho in vitro and induced the formation of stress fibers in NIH 3T3 fibroblasts. When MDCKII epithelial cells were treated with IGF-1, Rho and its effector Rho-associated kinase (Rho-kinase) were activated and actin stress fibers were enhanced. Furthermore, the IGF-1-induced Rho-kinase activation and the enhancement of stress fibers were inhibited by ectopic expression of the PDZ and RGS domains of LARG. Taken together, these results indicate that IGF-1 activates the Rho/Rho-kinase pathway via a LARG/IGF-1 receptor complex and thereby regulates cytoskeletal rearrangements.
authors.affiliation: Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Taya
authors.forename: N
authors.initials: N
authors.lastname: Inagaki
authors.forename: H
authors.initials: H
authors.lastname: Sengiku
authors.forename: H
authors.initials: H
authors.lastname: Makino
authors.forename: A
authors.initials: A
authors.lastname: Iwamatsu
authors.forename: I
authors.initials: I
authors.lastname: Urakawa
authors.forename: K
authors.initials: K
authors.lastname: Nagao
authors.forename: S
authors.initials: S
authors.lastname: Kataoka
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017930:Genes, Reporter; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000502:physiology*; D022502:Stress Fibers / Q000378:metabolism; D014018:Tissue Distribution; D020798:Two-Hybrid System Techniques; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: C577222:ARHGEF12 protein, human; C577223:Arhgef12 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D020741:rho GTP-Binding Proteins