Glycosyl phosphatidylinositol-anchored ceruloplasmin is expressed by rat Sertoli cells and is concentrated in detergent-insoluble membrane fractions.
The copper-binding protein, ceruloplasmin, is both a serum component and a secretory product of Sertoli cells. Studies on serum ceruloplasmin have demonstrated it to be a ferroxidase that is essential for iron transport throughout the body. We report here that a glycosyl phosphatidylinositol (GPI)-anchored form of ceruloplasmin is expressed by Sertoli cells. Sertoli cell GPI-anchored proteins were selectively released by phosphatidylinositol-specific phospholipase C and were analyzed by Western blotting. A 135-kDa band was identified as ceruloplasmin by multiple antibody recognition and by amino acid sequence analysis. The presence of the GPI anchor on ceruloplasmin was confirmed by Triton X-114 phase partitioning experiments and by recognition with an antibody to the GPI anchor. GPI-anchored ceruloplasmin was enriched in detergent-insoluble glycolipid-enriched membrane microdomains (DIGs) of Sertoli cells. This is the first report of GPI-anchored ceruloplasmin in Sertoli cells and the first study of GPI-anchored ceruloplasmin in DIGs. We suggest that GPI-anchored ceruloplasmin may be the dominant form expressed by Sertoli cells and that Sertoli cell DIGs may play a role in iron metabolism within the seminiferous tubule.
Fortna
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Department of Biology, Bucknell University, Lewisburg, Pennsylvania 17837, USA. fortna@mail.med.upenn.edu
Watson
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Nyquist
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D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002478:Cells, Cultured; D002570:Ceruloplasmin / Q000378:metabolism*; D003902:Detergents / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000378:metabolism*; D012995:Solubility; D010738:Type C Phospholipases / Q000378:metabolism
D003902:Detergents; D017261:Glycosylphosphatidylinositols; D002570:Ceruloplasmin; D010738:Type C Phospholipases