It is expressed on a diverse variety of cell types including most hematopoietic cells, keratinocytes, chondrocytes, many epithelial cell types, and some endothelial and neural cells. In this review we discuss the structural elements shown to be involved in specific functions. Therefore, the experiments discussed are primarily studies where wild type and mutant CD44 are transfected into cells whose function is then assayed. Column five lists representative publications documenting these experiments. ECM denotes extracellular matrix.
GAG denotes potential sites for the addition of glycosamino glycan side chains.
Features of the transmembrane and cytoplasmic domains of CD44. ERM denotes cytoskeletal associated proteins, ezrin, radixin, moesin. Although most details of CD44 structure will be discussed below, a brief description of the molecule is needed. Binding of the principal ligand of CD44, HA, is regulated. Active cells, expressing CD44 in an active state , can bind HA constitutively.