Ultrastructural immunogold localization of osteopontin in human gallbladder epithelial cells.
We used a post-embedding ultrastructural immunogold method to localize osteopontin in human gallbladder epithelial cells. This glycoprotein, originally described in bone but recently found to have a much wider distribution in many epithelia and in some mesenchymal cells, was present in the filamentous glycocalyx, small apical cytoplasmic smooth membrane-bound vesicles, large membrane-bound cytoplasmic granules, and in portions of the Golgi complex in gallbladder columnar epithelial cells. These findings suggest that newly synthesized osteopontin is packaged in Golgi-derived granules that release their contents by classical exocytosis from the cell surface. At least a portion of secreted osteopontin remains on the cell surface, where it becomes integrated into the filamentous glycocalyx coating the luminal surface of gallbladder epithelial cells.
Qu-Hong
Department of Pathology, Beth Israel Hospital, Boston, MA 02215.
Brown
L F
LF
Senger
D R
DR
Geng
L L
LL
Dvorak
H F
HF
Dvorak
A M
AM
D000595:Amino Acid Sequence; D002448:Cell Adhesion; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000648:ultrastructure; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry / Q000648:ultrastructure; D005704:Gallbladder / Q000737:chemistry* / Q000166:cytology / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000737:chemistry / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000737:chemistry / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron / Q000379:methods; D008969:Molecular Sequence Data; D009842:Oligopeptides; D053495:Osteopontin; D012795:Sialoglycoproteins / Q000032:analysis*
D009842:Oligopeptides; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin; C049554:glycyl-arginyl-glycyl-aspartyl-serine