Identification of a vitamin D-responsive protein on the surface of human osteosarcoma cells.
Monoclonal antibodies were elicited to membrane constituents of the osteoblastic human osteosarcoma cell line Saos-2. Two types of antibody reactivities were characterized: one group of antibodies identified fibroblastic and osteoblastic cultured cells, whereas the other group was specific for the parent cell line, Saos-2. Primary endothelial cells and hepatoma cells were not recognized by either group of antibodies. Through indirect immunofluorescent microscopy, the Saos-2-specific antigen was demonstrated to reside on the surface of these osteosarcoma cells. Metabolic radiolabeling of cultured Saos-2 cells and subsequent immunoprecipitation, electrophoretic separation, and autoradiography revealed this protein to have a Mr of 80,000. Similar experiments in the presence of hormones showed that the expression of this cell surface protein was influenced in an opposing fashion by the bone-regulating hormones parathyroid hormone and vitamin D. Vitamin D stimulated expression by 300%, whereas parathyroid hormone depressed expression by 50%. Thus, Saos-2 human osteoblastic cells demonstrate hormonal regulation through an apparently specific membrane protein.
Shull
S
S
Department of Biochemistry, University of Vermont Medical College, Burlington 05405.
Tracy
R P
RP
Mann
K G
KG
D000911:Antibodies, Monoclonal; D002117:Calcitriol / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D008970:Molecular Weight; D012516:Osteosarcoma / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D010281:Parathyroid Hormone; D002117:Calcitriol