title: Ultrastructural localization of bcl-2 protein.
abstract: Previous cell subfractionation studies have indicated that bcl-2 is an inner mitochondrial membrane protein. We have sought to determine the ultrastructural localization of bcl-2 protein in lymphoma and breast carcinoma cell lines and biopsy material known to overexpress bcl-2 using immunoelectron microscopy. To avoid the possibility of processing artifacts, samples were prepared by three different methods: progressive lowering of temperature, cryosectioning, and freeze-substitution. In all instances the labeling of bcl-2 protein was relatively weak but the distribution the same. In both lymphoma and breast carcinoma tissues, bcl-2 protein was detected on the periphery of mitochondria: little labeling of either the mitochondrial matrix or cristae could be detected. Labeling was also detected on the perinuclear membrane and throughout the cytoplasm, as also indicated by confocal microscopy. These data therefore indicate that bcl-2 protein can be detected at several intracellular sites and that at the likely functional destination, the mitochondria, there appears to be, contrary to expectations, a preferential association with the outer membrane.
authors.affiliation: Department of Cell Biology and Experimental Pathology, Institute of Cancer Research, Sutton, Surrey, UK.
authors.forename: P
authors.initials: P
authors.lastname: Monaghan
authors.forename: D
authors.initials: D
authors.lastname: Robertson
authors.forename: T A
authors.initials: TA
authors.lastname: Amos
authors.forename: M J
authors.initials: MJ
authors.lastname: Dyer
authors.forename: D Y
authors.initials: DY
authors.lastname: Mason
authors.forename: M F
authors.initials: MF
authors.lastname: Greaves
mesh_terms: D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000648:ultrastructure; D016616:Cryoultramicrotomy; D003593:Cytoplasm / Q000737:chemistry / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D017110:Freeze Substitution; D006801:Humans; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000737:chemistry / Q000648:ultrastructure*; D008223:Lymphoma / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure; D008854:Microscopy, Electron / Q000379:methods; D008928:Mitochondria / Q000737:chemistry / Q000648:ultrastructure; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D019253:Proto-Oncogene Proteins c-bcl-2; D013696:Temperature; D014407:Tumor Cells, Cultured
chemical_list: D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2