Immunoelectron microscopic demonstration of human melanosome associated antigens (HMSA) on melanoma cells: comparison with tyrosinase distribution.
Previously, we have developed a mouse monoclonal antibody (MoAb) HMSA-1 (human melanosome-associated antigen-1) against the melanosome fraction of human malignant melanoma, and demonstrated the selective distribution of the HMSA-1 in neoplastic melanocytes on routine paraffin sections. This study examined, by using enzyme linked immunosorbent assay (ELISA) and immunoelectron microscopy, the subcellular distribution of the HMSA-1 in malignant melanocytes. Fractionation of cell organelles and ELISA assay indicated that the HMSA-1 is rich in fractions of large granule, melanosome and endoplasmic reticulum (ER) in melanoma cells. Immunoelectron microscopic study showed that the HMSA-1 is localized in the melanosomes of various developmental stages and vacuolar structures, which appeared to be the stage I melanosomes and which contained the matrix protein. Dopa cytochemistry revealed that the distribution of MoAb HMSA-1 reaction product is localized in the area different from that of tyrosinase, indicating that the synthetic processes of melanosomal matrix protein and tyrosinase are different. Furthermore, the reaction product with MoAb HMSA-1 was seen in the rough ER, indicating that the melanosomal matrix protein is synthesized by membrane-bound ribosomes and processed through the channel of ER.
D000911:Antibodies, Monoclonal / Q000276:immunology; D000951:Antigens, Neoplasm / Q000032:analysis*; D004156:Catechol Oxidase / Q000032:analysis*; D004295:Dihydroxyphenylalanine / Q000032:analysis; D004721:Endoplasmic Reticulum / Q000032:analysis; D006801:Humans; D008544:Melanocytes / Q000276:immunology*; D008545:Melanoma / Q000201:enzymology / Q000276:immunology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D014442:Monophenol Monooxygenase / Q000032:analysis*
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D004295:Dihydroxyphenylalanine; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase