RESUMO
Interleukin-6 (IL-6) induces the activation of the Src family kinase Hck, which is associated with the IL-6 receptor beta-chain, gp130. Here we describe the identification of an "acidic" domain comprising amino acids 771 to 811 of gp130 as a binding region for Hck, which mediates proliferative signaling. The deletion of this region of gp130 (i.e., in deletion mutant d771-811) resulted in a significant reduction of Hck kinase activity and cell proliferation upon stimulation of gp130 compared to wild-type gp130. In addition, d771-811 disrupted the growth factor-stimulated activation of Erk and the dephosphorylation of Pyk2. Based on these findings, we propose a novel, acidic domain of gp130, which is responsible for the activation of Hck, Erk, and Pyk2 and signals cell proliferation upon growth factor stimulation.
Assuntos
Antígenos CD/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas Tirosina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Transdução de Sinais/fisiologia , Motivos de Aminoácidos/fisiologia , Animais , Antígenos CD/genética , Divisão Celular/efeitos dos fármacos , Divisão Celular/fisiologia , Linhagem Celular , Receptor gp130 de Citocina , Proteínas de Ligação a DNA/metabolismo , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/fisiologia , Inibidores Enzimáticos/farmacologia , Quinase 2 de Adesão Focal , Substâncias de Crescimento/farmacologia , Humanos , Interleucina-6/metabolismo , Interleucina-6/farmacologia , Glicoproteínas de Membrana/genética , Camundongos , Mutagênese Sítio-Dirigida , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Estrutura Terciária de Proteína/fisiologia , Proteínas Proto-Oncogênicas c-hck , Receptores da Eritropoetina/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Fator de Transcrição STAT3 , Transdução de Sinais/efeitos dos fármacos , Transativadores/metabolismo , TransfecçãoRESUMO
Matrix remodeling, degradation, inflammation and invasion liberate peptide fragments that can subsequently interact with cells in an attachment-independent manner. Such 'soluble' matrix components, including collagens, fibronectin and laminin, induced Smad activation (termed crosstalk signaling), which follows a similar chronological sequence and R-Smad specificity as induced by transforming growth factor (TGF)-beta1. Smad4 nuclear translocation occurred in response to collagen binding, indicating downstream signal propagation. TGF-beta scavenging antibody affected only TGF-beta1, but not crosstalk-induced responses. TGF-beta type II receptor mutation (DR26Delta25), which is deficient in TGF-beta type I receptor recruitment to the ligand, induced a heterotetramer signaling complex, and propagated Smad2 activation only through collagen induction and not TGF-beta signaling. Consequentially, TGF-beta ligand participation is not required for crosstalk signaling. This signaling requires a functional integrin beta1 receptor as showed by RNA interference. Co-immunoprecipitation (co-IP) and fluorescent microscopy indicate the involvement of focal adhesion kinase (FAK) and Src activity in collagen-induced signal propagation, and suggest a membrane signaling complex formation that includes both TGF-beta receptors and integrins. The related gene expressional responses are distinct from that evoked by TGF-beta1, supporting its separate function. This signaling mechanism expands and partially explains TGF-beta receptor dynamics and consequential signaling diversity-related gene expressional plasticity.