RESUMO
Carcinoma cells selected for their ability to migrate in vitro showed enhanced invasive properties in vivo. Associated with this induction of migration was the anchorage-dependent phosphorylation of p130CAS (Crk-associated substrate), leading to its coupling to the adaptor protein c-CrkII (Crk). In fact, expression of CAS or its adaptor protein partner Crk was sufficient to promote cell migration, and this depended on CAS tyrosine phosphorylation facilitating an SH2-mediated complex with Crk. Cytokine-stimulated cell migration was blocked by CAS lacking the Crk binding site or Crk containing a mutant SH2 domain. This migration response was characterized by CAS/Crk localization to membrane ruffles and blocked by the dominant-negative GTPase, Rac, but not Ras. Thus, CAS/Crk assembly serves as a "molecular switch" for the induction of cell migration and appears to contribute to the invasive property of tumors.
Assuntos
Movimento Celular/fisiologia , Fosfoproteínas/metabolismo , Proteínas , Proteínas Proto-Oncogênicas/metabolismo , Animais , Células COS , Membrana Celular/química , Membrana Celular/metabolismo , Movimento Celular/efeitos dos fármacos , Proteína Substrato Associada a Crk , Matriz Extracelular/fisiologia , Proteínas de Ligação ao GTP/química , Proteínas de Ligação ao GTP/metabolismo , Expressão Gênica/genética , Expressão Gênica/fisiologia , Humanos , Hipoglicemiantes/farmacologia , Insulina/farmacologia , Proteínas de Membrana/análise , Metástase Neoplásica , Pâncreas/citologia , Pâncreas/patologia , Pâncreas/fisiopatologia , Neoplasias Pancreáticas/patologia , Fosfoproteínas/efeitos dos fármacos , Fosfoproteínas/genética , Fosforilação , Ligação Proteica , Proteínas Proto-Oncogênicas/efeitos dos fármacos , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-crk , Coelhos , Proteína p130 Retinoblastoma-Like , Células Tumorais Cultivadas , Tirosina/metabolismo , Proteínas rac de Ligação ao GTP , Proteínas ras/química , Proteínas ras/metabolismo , Domínios de Homologia de srcRESUMO
An Alu element preceding the myeloperoxidase gene (MPO) contains four hexamer motifs related to the consensus recognition sequence for nuclear hormone receptors (AGGTCA), arranged as direct repeats with spacing of 2, 4, and 2 nucleotides (DR-2-4-2). Gel shift experiments and transient transfection assays demonstrate that these sequences include binding sites for retinoic acid and thyroid hormone receptors and function in vivo to activate transcription of a chloramphenicol acetyltransferase reporter gene. The first DR-2 elements of the series do not bind known receptors but do bind the SP1 transcription factor. Two alleles of the MPO gene exist that differ at one position within this element, resulting in one allele with and one without a strong SP1 binding site. The element with the SP1 site activates transcription by 25-fold in transient transfection assays, while the alternative allele confers severalfold less transcriptional activity. Most cases of acute myelocytic leukemia are homozygous for the allele with the SP1 binding site, suggesting this element plays an important role in regulating the MPO gene in myeloid leukemias. This MPO-Alu is a representative of an Alu subclass numbering approximately 400,000 copies, suggesting many genes may be regulated by such elements.
