| First Author | Uemura S | Year | 2009 |
| Journal | Mol Biol Cell | Volume | 20 |
| Issue | 13 | Pages | 3088-100 |
| PubMed ID | 19420140 | Mgi Jnum | J:306484 |
| Mgi Id | MGI:6711026 | Doi | 10.1091/mbc.e08-12-1219 |
| Citation | Uemura S, et al. (2009) The cytoplasmic tail of GM3 synthase defines its subcellular localization, stability, and in vivo activity. Mol Biol Cell 20(13):3088-100 |
| abstractText | GM3 synthase (SAT-I) is the primary glycosyltransferase responsible for the biosynthesis of ganglio-series gangliosides. In this study, we identify three isoforms of mouse SAT-I proteins, named M1-SAT-I, M2-SAT-I, and M3-SAT-I, which possess distinct lengths in their NH(2)-terminal cytoplasmic tails. These isoforms are produced by leaky scanning from mRNA variants of mSAT-Ia and mSAT-Ib. M2-SAT-I and M3-SAT-I were found to be localized in the Golgi apparatus, as expected, whereas M1-SAT-I was exclusively found in the endoplasmic reticulum (ER). Specific multiple arginines (R) arranged in an R-based motif, RRXXXXR necessary for ER targeting, were found in the cytoplasmic tail of M1-SAT-I, and in vivo GM3 biosynthesis by M1-SAT-I was very low because of restricted transport to the Golgi apparatus. In addition, M1-SAT-I and M3-SAT-I had a long half-life relative to M2-SAT-I. This is the first report demonstrating the presence of an ER-targeting R-based motif in the cytoplasmic tail of a protein in the mammalian glycosyltransferase family of enzymes. The system, which produces SAT-I isoforms having distinct characteristics, is likely to be of critical importance for the regulation of GM3 biosynthesis under various pathological and physiological conditions. |
