Members of the Nucleotide-Sugar Transporter Family and their Functions

Abstract

Glycosylation and sulfation are important posttranslational modifications of proteins and are performed in the lumens of the endoplasmic reticulum (ER) or the Golgi apparatus by glycosyltransferases and sulfotransferases, respectively. However, the donor substrates of transferases, nucleotide sugars and 3’-phosphoadenosine 5’-phosphosulfate (PAPS), are synthesized in the cytosol or nucleus. Nucleotide-sugar transporters (NSTs) or PAPST transporters (PAPSTs) transport nucleotide sugar or PAPS into the lumen of the ER and the Golgi and therefore determine the glycosylation or sulfation status by supplying donor substrates. These transporters belong to the NST family, solute carrier 35 (SLC35). In this chapter, all transporters with known transport activities are described. In addition, the methods used for the measurement of their transferase activities and their functional analysis using RNA interference (RNAi) are described.