Drosophila GPI-mannosyltransferase 2 is required for GPI anchor attachment and surface expression of chaoptin

Vis Neurosci. 2012 May;29(3):143-56. doi: 10.1017/S0952523812000181. Epub 2012 May 10.


Glycosylphosphatidylinositol (GPI) anchors are critical for the membrane attachment of a wide variety of essential signaling and cell adhesion proteins. The GPI anchor is a complex glycolipid structure that utilizes glycosylphosphatidylinositol-mannosyltransferases (GPI-MTs) for the addition of three core mannose residues during its biosynthesis. Here, we demonstrate that Drosophila GPI-MT2 is required for the GPI-mediated membrane attachment of several GPI-anchored proteins, including the photoreceptor-specific cell adhesion molecule, chaoptin. Mutations in gpi-mt2 lead to defects in chaoptin trafficking to the plasma membrane in Drosophila photoreceptor cells. In gpi-mt2 mutants, loss of sufficient chaoptin in the membrane leads to microvillar instability, photoreceptor cell pathology, and retinal degeneration. Finally, using site-directed mutagenesis, we have identified key amino acids that are essential for GPI-MT2 function and cell viability in Drosophila. Our findings on GPI-MT2 provide a mechanistic link between GPI anchor biosynthesis and protein trafficking in Drosophila and shed light on a novel mechanism for inherited retinal degeneration.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Animals, Genetically Modified
  • Blotting, Western
  • Cell Membrane / metabolism
  • Cell Survival / physiology
  • DNA / genetics
  • Drosophila / metabolism*
  • Drosophila Proteins / biosynthesis*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Glycosylphosphatidylinositols / genetics
  • Glycosylphosphatidylinositols / metabolism*
  • Humans
  • Immunohistochemistry
  • Mannosyltransferases / genetics
  • Mannosyltransferases / metabolism*
  • Membrane Glycoproteins / biosynthesis*
  • Microscopy, Electron
  • Microvilli / metabolism
  • Molecular Sequence Data
  • Mutagenesis
  • Opsins / metabolism
  • Photoreceptor Cells, Invertebrate / metabolism
  • Protein Conformation
  • Receptors, Cell Surface / biosynthesis*
  • Species Specificity


  • Drosophila Proteins
  • Glycosylphosphatidylinositols
  • Membrane Glycoproteins
  • Opsins
  • Receptors, Cell Surface
  • chp protein, Drosophila
  • DNA
  • Mannosyltransferases
  • veg protein, Drosophila