Figure 7. Sequence and cellular domains of human syndecan 4. The sequence from amino acid 1 to 18 represents the signal peptide and is usually cleaved out in the endoplasmic reticulum before the protein is trafficked to the cell surface. Sequence from 19 to 45 represents the extracellular domain of the protein. Sequence from 146 to 170 represents the transmembrane domain and the sequence from 171 to 198 represents the C-terminal cytoplasmic domain. Gray highlights tryptic peptides that were detected and identified by LC-MS/MS analysis. Note that all the detected peptides belonged to the extracellular domain of the protein suggesting that syndecan 4 sheds its ectodomain into the condition medium in response to TNF-α treatment.