RESUMO
Transforming growth factor-beta (TGF-beta) superfamily related growth factors signal by binding to transmembrane type I and type II receptor serine/threonine kinases (RSTK), which phosphorylate intracellular Smad transcription factors in response to ligand binding. Here we describe the cloning of the human type I RSTK activin receptor-like kinase 7 (ALK7), an orthologue of the previously identified rat ALK7. Nodal, a TGF-beta member expressed during embryonic development and implicated in developmental events like mesoderm formation and left-right axis specification, was recently shown to signal through ALK7. We found ALK7 mRNA to be most abundantly expressed in human brain, pancreas and colon. A cDNA encoding the open reading frame of ALK7 was obtained from a human brain cDNA library. Furthermore, a P1 artificial chromosome (PAC) clone containing the human ALK7 gene was isolated and fluorescent in situ hybridization (FISH) on metaphase chromosomes identified the gene locus as chromosome 2q24.1-->q3. To test the functionality of the ALK7 signaling, we generated recombinant adenoviruses containing a constitutively active form of ALK7 (Ad-caALK7), which is capable of activating downstream targets in a ligand independent manner. Infection with Ad-caALK7 of MIN6 insulinoma cells, in which ALK7 has previously been shown to be endogenously expressed, led to a marked increase in the phosphorylation of Smad2, a signaling molecule also used by TGF-betas and activins.
Assuntos
Receptores de Ativinas Tipo I/genética , Química Encefálica/genética , Proteínas Serina-Treonina Quinases/genética , Receptores de Ativinas Tipo I/metabolismo , Sequência de Aminoácidos , Mapeamento Cromossômico , Clonagem Molecular , Proteínas de Ligação a DNA/metabolismo , Expressão Gênica , Biblioteca Gênica , Humanos , Insulinoma/genética , Dados de Sequência Molecular , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais/genética , Proteína Smad2 , Transativadores/metabolismo , Células Tumorais CultivadasRESUMO
BACKGROUND: Vascular endothelial growth factor (VEGF) is a hypoxia-induced endothelial cell-specific mitogen, which is angiogenic in vivo and up-regulated in several malignancies. VEGF can be used as a prognostic marker, but the effect of surgical trauma on serum VEGF (S-VEGF) concentrations is unknown and might reduce the value of VEGF as a serum marker. METHODS: We monitored S-VEGF levels by enzyme-linked immunosorbent assay in patients undergoing surgery. RESULTS: Eighteen patients with major surgery had slightly elevated S-VEGF compared with the preoperative level (median 9.5 pg/mL) on the first (median 35 pg/mL; P = 0.0002) and third (median 19 pg/mL; P = 0.004) postoperative day, but not in later samples. The levels measured in 8 patients after minor surgery did not differ from the preoperative levels (P = 0.14). CONCLUSIONS: Even major surgery is associated only with a slight and transient increase in S-VEGF levels, and, therefore, is unlikely to interfere markedly with the use of VEGF as a prognostic marker.
