Characterization of a 66-kilodalton surface glycoprotein of the human corneal endothelium.
The pellet recovered after centrifugation (5000 X g) of human corneal endothelial homogenates was used as the source of membranes in these studies. A 66-kilodalton (kD) protein was identified as the most abundant protein in the particulate pellet by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The de novo synthesis of the 66-kD protein by endothelial cells was observed during culturing of human corneas in the presence of 35S-methionine. The 66-kD protein was found to be a plasma membrane protein based on several of its properties, ie, its solubility in CHCl3:CH3OH, its labeling as surface glycoprotein, and during exposure to a photoaffinity hydrophobic probe: 1-azido-4-125I-iodobenzene. Furthermore this protein could be released from the particulate pellet after treatment with phosphatidylinositol-specific phospholipase C, suggesting its anchorage via a phosphatidylinositol glycan linkage in the plasma membrane. Such anchorage of this protein was further confirmed by its labeling during culture of corneas in the presence of 3H-myoinositol. The glycoprotein nature of the 66-kD protein was evident from its labeling during surface glycoprotein labeling of endothelial cells, staining with periodic acid-Schiff stain, and binding to peanut agglutinin (PNA), and lotus agglutinin (LTA) on SDS-acrylamide gels. The 66-kD protein of endothelial particulate pellets recovered from corneas of donors of different ages showed an age-related increase in binding to PNA and LTA. This suggested an increased glycosylation of the 66-kD protein with aging. A polyclonal anti-66-kD protein antibody was used as a probe to determine the presence of this protein in the rabbit and bovine corneal endothelia by the Western-blot analysis. The 66-kD protein was detected in both rabbit and bovine endothelia, but an additional immunoreactive species of 17 kD was also observed which may be a processed product of the 66-kD protein.
Missouri Lions Eye Research Foundation, Columbia 65201.
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D000375:Aging / Q000378:metabolism; D000818:Animals; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D004728:Endothelium, Corneal / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D006031:Glycosylation; D017261:Glycosylphosphatidylinositols; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D010716:Phosphatidylinositols / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D011817:Rabbits; D012995:Solubility
D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010716:Phosphatidylinositols; D011134:Polysaccharides