Secreted int-1 protein is associated with the cell surface.
The murine int-1 proto-oncogene has been implicated in neural development and, when transcriptionally activated by mouse mammary tumor virus, contributes to the genesis of mammary tumors. To understand the function of the int-1 gene product in these processes, we have characterized the biochemical properties of int-1 protein expressed in a neuroendocrine cell line transfected with int-1 cDNA. Here we provide evidence that int-1 protein is secreted and associates with the cell surface. int-1 protein was very efficiently processed and secreted through the constitutive secretory pathway, although no int-1 protein could be immunoprecipitated from the culture medium. Treatment with suramin effectively released mature int-1 proteins into the culture fluid, which suggests that secreted int-1 protein associates with the cell surface or extracellular matrix. We have also shown directly, by radioiodination of intact cells and by surface antibody adsorption, that secreted int-1 proteins can be detected on the cell surface. These data support a model in which int-1 protein is secreted and functions locally in cell-to-cell signaling.
Papkoff
J
J
Institute of Cancer and Developmental Biology, Syntex Research, Palo Alto, California 94304.
Schryver
B
B
D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex / Q000032:analysis; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D005822:Genetic Vectors; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D011519:Proto-Oncogenes; D013462:Sulfur Radioisotopes; D013498:Suramin / Q000494:pharmacology; D014162:Transfection; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins
D000906:Antibodies; D000936:Antigen-Antibody Complex; D011518:Proto-Oncogene Proteins; D013462:Sulfur Radioisotopes; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins; D013498:Suramin; D003545:Cysteine