title: Association of p60c-src with endosomal membranes in mammalian fibroblasts.
abstract: We have examined the subcellular localization of p60c-src in mammalian fibroblasts. Analysis of indirect immunofluorescence by three-dimensional optical sectioning microscopy revealed a granular cytoplasmic staining that co-localized with the microtubule organizing center. Immunofluorescence experiments with antibodies against a number of membrane markers demonstrated a striking co-localization between p60c-src and the cation-dependent mannose-6-phosphate receptor (CI-MPR), a marker that identifies endosomes. Both p60c-src and the CI-MPR were found to cluster at the spindle poles throughout mitosis. In addition, treatment of interphase and mitotic cells with brefeldin A resulted in a clustering of p60c-src and CI-MPR at a peri-centriolar position. Biochemical fractionation of cellular membranes showed that a major proportion of p60c-src co-enriched with endocytic membranes. Treatment of membranes containing HRP to alter their apparent density also altered the density of p60c-src-containing membranes. Similar density shift experiments with total cellular membranes revealed that the majority of membrane-associated p60c-src in the cell is associated with endosomes, while very little is associated with plasma membranes. These results support a role for p60c-src in the regulation of endosomal membranes and protein trafficking.
authors.affiliation: Department of Microbiology, University of California, San Francisco 94143.
authors.forename: K B
authors.initials: KB
authors.lastname: Kaplan
authors.forename: J R
authors.initials: JR
authors.lastname: Swedlow
authors.forename: H E
authors.initials: HE
authors.lastname: Varmus
authors.forename: D O
authors.initials: DO
authors.lastname: Morgan
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D004705:Endocytosis; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008938:Mitosis; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D014162:Transfection
chemical_list: D016392:Proto-Oncogene Proteins pp60(c-src)