ABSTRACT
GPI-anchored proteins (GPI-APs) play an important role in a variety of plant biological processes including growth, stress response, morphogenesis, signalling and cell wall biosynthesis. The GPI-anchor contains a lipid-linked glycan backbone that is synthesized in the endoplasmic reticulum (ER) where it is subsequently transferred to the C-terminus of proteins containing a GPI signal peptide by a GPI transamidase. Once the GPI anchor is attached to the protein, the glycan and lipid moieties are remodelled. In mammals and yeast, this remodelling is required for GPI-APs to be included in Coat Protein II (COPII) coated vesicles for their ER export and subsequent transport to the cell surface. The first reaction of lipid remodelling is the removal of the acyl chain from the inositol group by Bst1p (yeast) and PGAP1 (mammals). In this work, we have used a loss-of-function approach to study the role of PGAP1/Bst1 like genes in plants. We have found that Arabidopsis PGAP1 localizes to the ER and probably functions as the GPI inositol-deacylase which cleaves the acyl chain from the inositol ring of the GPI anchor. In addition, we show that PGAP1 function is required for efficient ER export and transport to the cell surface of GPI-APs.
One sentence summary GPI anchor lipid remodeling in GPI-anchored proteins is required for their transport to the cell surface in Arabidopsis.
Footnotes
1 F.A. and M.J.M. were supported by the Ministerio de Economía y Competitividad (grant no BFU2016-76607-P). C.B.S. and J.S.S. were recipients of a fellowship from Ministerio de Ciencia, Innovación y Universidades (FPU program). C.B.S. was also recipient of an EMBO short-term fellowship.
F.A., K.J. and M.J.M. conceived and designed the experiments. C.B.S., J.S.S and Y.M. performed the experiments. F.A. and M.J.M. wrote the paper, with input from all other authors.