Identification of a Golgi GPI-N-acetylgalactosamine transferase with tandem transmembrane regions in the catalytic domain

Many eukaryotic proteins are anchored to the cell surface via the glycolipid glycosylphosphatidylinositol (GPI). Mammalian GPIs have a conserved core but exhibit diverse N -acetylgalactosamine (GalNAc) modifications, which are added via a yet unresolved process. Here we identify the Golgi-resident G...

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Veröffentlicht in:Nature communications 2018-01, Vol.9 (1), p.405-16, Article 405
Hauptverfasser: Hirata, Tetsuya, Mishra, Sushil K., Nakamura, Shota, Saito, Kazunobu, Motooka, Daisuke, Takada, Yoko, Kanzawa, Noriyuki, Murakami, Yoshiko, Maeda, Yusuke, Fujita, Morihisa, Yamaguchi, Yoshiki, Kinoshita, Taroh
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Sprache:eng
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Zusammenfassung:Many eukaryotic proteins are anchored to the cell surface via the glycolipid glycosylphosphatidylinositol (GPI). Mammalian GPIs have a conserved core but exhibit diverse N -acetylgalactosamine (GalNAc) modifications, which are added via a yet unresolved process. Here we identify the Golgi-resident GPI-GalNAc transferase PGAP4 and show by mass spectrometry that PGAP4 knockout cells lose GPI-GalNAc structures. Furthermore, we demonstrate that PGAP4, in contrast to known Golgi glycosyltransferases, is not a single-pass membrane protein but contains three transmembrane domains, including a tandem transmembrane domain insertion into its glycosyltransferase-A fold as indicated by comparative modeling. Mutational analysis reveals a catalytic site, a DXD-like motif for UDP-GalNAc donor binding, and several residues potentially involved in acceptor binding. We suggest that a juxtamembrane region of PGAP4 accommodates various GPI-anchored proteins, presenting their acceptor residue toward the catalytic center. In summary, we present insights into the structure of PGAP4 and elucidate the initial step of GPI-GalNAc biosynthesis. Mammalian GPI membrane anchors are modified by GalNAc to confer structural diversity but the biosynthetic pathway is poorly understood. Here, the authors identify and characterize the Golgi-resident GPI-GalNAc transferase PGAP4, providing insights into the initial step of GPI-GalNAc biosynthesis.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-017-02799-0