Distinct functional units of the Golgi complex in Drosophila cells
- Hiroyuki Yano*,†,
- Miki Yamamoto-Hino*,†,‡,
- Masato Abe*,
- Reiko Kuwahara*,
- Shuka Haraguchi*,
- Isamu Kusaka*,‡,§,
- Wakae Awano*,
- Akiko Kinoshita-Toyoda‡,¶,
- Hidenao Toyoda‡,§,¶, and
- Satoshi Goto*,‡,§,∥
- *Mitsubishi-Kagaku Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan; ‡Core Research for Evolutionary Science and Technology (CREST) and §Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan; and ¶Faculty of Pharmaceutical Sciences, Chiba University, Inage, Chiba 263-8522, Japan
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Communicated by Sen-itiroh Hakomori, Pacific Northwest Research Institute, Seattle, WA, August 8, 2005 (received for review January 31, 2005)
Abstract
A striking variety of glycosylation occur in the Golgi complex in a protein-specific manner, but how this diversity and specificity are achieved remains unclear. Here we show that stacked fragments (units) of the Golgi complex dispersed in Drosophila imaginal disk cells are functionally diverse. The UDP-sugar transporter FRINGE-CONNECTION (FRC) is localized to a subset of the Golgi units distinct from those harboring SULFATELESS (SFL), which modifies glucosaminoglycans (GAGs), and from those harboring the protease RHOMBOID (RHO), which processes the glycoprotein SPITZ (SPI). Whereas the glycosylation and function of NOTCH are affected in imaginal disks of frc mutants, those of SPI and of GAG core proteins are not, even though FRC transports a broad range of glycosylation substrates, suggesting that Golgi units containing FRC and those containing SFL or RHO are functionally separable. Distinct Golgi units containing FRC and RHO in embryos could also be separated biochemically by immunoisolation techniques. We also show that Tn-antigen glycan is localized only in a subset of the Golgi units distributed basally in a polarized cell. We propose that the different localizations among distinct Golgi units of molecules involved in glycosylation underlie the diversity of glycan modification.
