RESUMEN
Syncytin-1, the envelope protein of ERVWE1, an endogenous retrovirus of the HERV-W family, plays an important role in regulating fusion of the placental trophoblast. At least one of its receptors is expressed on a variety of human cell types. Its ability to fuse cells makes it an attractive candidate molecule in gene therapy against cancer. We studied the relevance of sequences in the cytoplasmic tail of syncytin-1 for inducing cell-cell fusion. We generated a series of C-terminally truncated syncytin-1 variants. Sequences immediately adjacent to the transmembrane region of syncytin-1 were necessary for inducing optimal fusion, whereas the extreme C-terminus of syncytin-1 partially inhibited its fusogenicity. Two variants of syncytin-1, truncated after residues 483 and 515, were significantly hyperfusogenic compared to wild-type syncytin-1. Cellular and cell-surface expression levels of these two variant proteins were similar to those of wild-type syncytin-1. In testing the latter we found that only a very minor portion of recombinantly expressed cellular syncytin-1 was fully mature and expressed on the cell surface. Our results contribute to the understanding of the structure-function relationship of syncytin-1, and might have implications for the use of this molecule in gene therapy.
Asunto(s)
Productos del Gen env/genética , Productos del Gen env/fisiología , Proteínas Gestacionales/genética , Proteínas Gestacionales/fisiología , Animales , Biotinilación , Western Blotting , Células CHO , Extractos Celulares/química , Línea Celular Tumoral , Membrana Celular/metabolismo , Cricetinae , Regulación de la Expresión Génica/genética , Productos del Gen env/química , Productos del Gen env/metabolismo , Variación Genética , Humanos , Proteínas Gestacionales/química , Proteínas Gestacionales/metabolismo , ARN Mensajero/genética , ARN Mensajero/fisiología , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Propiedades de SuperficieRESUMEN
As islet transplantation becomes an acceptable clinical modality for restoring normoglycemia in type 1 diabetic patients, there is a crucial need for noninvasive assessment of the fate of the grafts. In spite of the success of the Edmonton Protocol, a significant graft loss occurs due to immunological and nonimmunological events immediately after transplantation. Allogeneic rejection in graft recipients is one of the major reasons for islet death and graft failure. Therefore, monitoring the islet rejection using reliable noninvasive methods would significantly aid in clinical assessment of graft success. We have previously developed a method to detect transplanted islets noninvasively using magnetic resonance imaging (MRI). For this procedure, human pancreatic islets are labeled with an MRI contrast agent that enables their visualization on magnetic resonance images. In our present study, we not only detected labeled human islets in a preclinical intrahepatic model of human islet transplantation in mice but also showed that islet rejection can be monitored noninvasively and repeatedly in real time by MRI. In addition, in this study, we have adapted, for islet cell labeling, a Food and Drug Administration-approved commercially available contrast agent, Feridex, that is used clinically for liver imaging. We believe that this agent, in combination with our preclinical model of islet transplantation, will facilitate the transition of imaging immune rejection to clinical trials.