Anchoring and degradation of glycolipid-anchored membrane proteins by L929 versus by LM-TK- mouse fibroblasts: implications for anchor biosynthesis.

Although many cells anchor surface proteins via moieties that are sensitive to phosphatidylinositol-specific phospholipase C (PI-PLC), the anchor moieties of surface proteins of mouse L929 cells resist PI-PLC. By constructing stable hybrids between L929 and lymphoma cells that express glycolipid-anchored proteins in a PI-PLC-sensitive form, we show that PI-PLC resistance behaves as a recessive trait. Since putative mannolipid precursors of the lipid anchors bear alkali-labile substituents which make them resist PI-PLC, these observations are most simply interpreted by postulating that L929 lacks a critical anchor deacylase. Unlike the L929 cell line, two of its descendants, the LM cell line and its thymidine kinase-negative variant (LM-TK-), do not express glycolipid-anchored proteins on their surface. Moreover, unlike L929 cells, LM-TK- cells rapidly inactivate at least one lipid-anchored enzyme in a compartment sensitive to acidotropic amines and leupeptin. By fusion of LM-TK- cells to mouse Thy-1- lymphoma mutants and monitoring of surface expression of lipid-anchored proteins, we assign LM-TK- to lymphoma mutant complementation group H. This genetic assignment is matched by analysis of mannolipids of L929, LM-TK-, wild-type, and class H lymphoma mutant cells: striking similarities are seen between the two wild-type cells by contrast to the mutants. Since the differences pertain to lipids which have properties consistent with their being anchor precursors, we suggest that LM-TK- has a lesion in the synthesis of anchor precursor mannolipids.
AuthorsN Singh, D Singleton, A M Tartakoff
JournalMolecular and cellular biology (Mol Cell Biol) Vol. 11 Issue 5 Pg. 2362-74 (May 1991) ISSN: 0270-7306 [Print] UNITED STATES
PMID1826759 (Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Glycolipids
  • Glycosylphosphatidylinositols
  • Membrane Proteins
  • Phosphatidylinositols
  • Thymidine Kinase
  • Alkaline Phosphatase
  • Type C Phospholipases
  • Alkaline Phosphatase (genetics, metabolism)
  • Animals
  • Cell Fusion
  • Cell Membrane (metabolism, ultrastructure)
  • Fibroblasts (metabolism)
  • Fluorescent Antibody Technique
  • Genetic Complementation Test
  • Genetic Variation
  • Glycolipids (metabolism)
  • Glycosylphosphatidylinositols
  • Kinetics
  • L Cells (Cell Line) (cytology, metabolism, ultrastructure)
  • Lymphoma
  • Membrane Proteins (metabolism)
  • Mice
  • Phosphatidylinositols (metabolism)
  • Thymidine Kinase (genetics)
  • Transfection
  • Type C Phospholipases (metabolism)

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