Production of the glycosylphosphatidylinositol-specific phospholipase D by the islets of Langerhans.
A large number of diverse cell surface proteins are anchored to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. One proposed function for the GPI anchor is that it facilitates the release of the protein from the cell by acting as a target for anchor-specific phospholipases. We and others have discovered that mammalian plasma contains a GPI-specific phospholipase D (GPI-PLD) (Cardoso de Almeida, M. L., Turner, M. J., Stambuk, B. V., and Schenkman, S. (1988) Biochem, Biophys. Res. Commun. 150, 476-482; Davitz, M. A., Hereld, D., Shak, S., Krakow, J., Englund, P. T., and Nussenzweig, V. (1987) Science 238, 81-84; Low, M. G., and Prasad, A. R. S. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 980-984). Because the GPI-PLD recognizes a conserved portion of the anchor, all GPI-anchored proteins are potential substrates for the enzyme. We demonstrate in this communication the production of the plasma GPI-PLD by the islets of Langerhans. GPI-PLD enzymatic activity was found in dog pancreatic microsomes, but not pancreatic juice. Both the pancreatic and plasma enzymes were divalent cation-dependent and had identical substrate specificities. Purified murine islets of Langerhans, as well as alpha and beta cells, contained and released GPI-PLD activity. A GPI-PLD DNA fragment was amplified by polymerase chain reaction from a normal human islet cDNA library; the amplified fragment hybridized with the GPI-PLD cDNA clone. These findings represent the first demonstration of the production of the plasma GPI-PLD by a specific tissue site as well as cell type.
Metz
C N
CN
Department of Pathology, New York University School of Medicine, New York 10016.
Zhang
Y Y
YY
Guo
Y
Y
Tsang
T C
TC
Kochan
J P
JP
Altszuler
N
N
Davitz
M A
MA
D000818:Animals; D015139:Blotting, Southern; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D006017:Glycolipids / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols; D006801:Humans; D007515:Islets of Langerhans / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010739:Phospholipase D / Q000096:biosynthesis* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051381:Rats; D013379:Substrate Specificity; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000378:metabolism
D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols; D014643:Variant Surface Glycoproteins, Trypanosoma; D010739:Phospholipase D