Protein O-fucosyltransferase 2 adds O-fucose to thrombospondin type 1 repeats.
O-Fucose is an unusual form of glycosylation found on epidermal growth factor-like (EGF) repeats and thrombospondin type 1 repeats (TSRs) in many secreted and transmembrane proteins. Recently O-fucose on EGF repeats was shown to play important roles in Notch signaling. In contrast, physiological roles for O-fucose on TSRs are unknown. In the accompanying paper (Luo, Y., Nita-Lazar, A., and Haltiwanger, R. S. (2006) J. Biol. Chem. 281, 9385-9392), we demonstrated that an enzyme distinct from protein O-fucosyltransferase 1 adds O-fucose to TSRs. A known homologue of O-fucosyltransferase 1 is putative protein O-fucosyltransferase 2. The cDNA sequence encoding O-fucosyltransferase 2 was originally identified during a data base search for fucosyltransferases in Drosophila. Like O-fucosyltransferase 1, O-fucosyltransferase 2 is conserved from Caenorhabditis elegans to humans. Although O-fucosyltransferase 2 was assumed to be another protein O-fucosyltransferase, no biochemical characterization existed supporting this contention. Here we show that RNAi-mediated reduction of the O-fucosyltransferase 2 message significantly decreased TSR-specific O-fucosyltransferase activity in Drosophila S2 cells. We also found that O-fucosyltransferase 2 is predominantly localized in the endoplasmic reticulum compartment of these cells. Furthermore, we expressed recombinant Drosophila O-fucosyltransferase 2 and showed that it O-fucosylates TSRs but not EGF repeats in vitro. These results demonstrate that O-fucosyltransferase 2 is in fact a TSR-specific O-fucosyltransferase.
Luo
Yi
Y
Department of Biochemistry and Cell Biology, Institute for Cell and Developmental Biology, Stony Brook University, Stony Brook, New York 11794-5215, USA.
Koles
Kate
K
Vorndam
Wendy
W
Haltiwanger
Robert S
RS
Panin
Vladislav M
VM
D000595:Amino Acid Sequence; D000818:Animals; D018929:Cell Culture Techniques; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005647:Fucosyltransferases / Q000235:genetics* / Q000378:metabolism*; D020869:Gene Expression Profiling; D006031:Glycosylation; D008969:Molecular Sequence Data; D034622:RNA Interference; D019700:Thrombospondin 1 / Q000378:metabolism*; D000097631:Galactoside 2-alpha-L-fucosyltransferase
D029721:Drosophila Proteins; D005647:Fucosyltransferases; D019700:Thrombospondin 1; D000097631:Galactoside 2-alpha-L-fucosyltransferase; C471275:O-fucosyltransferase 1, Drosophila