Current Topics in Microbiology and Immunology (1993) Volume on Adhesion in Leukocyte Homing and Differentiation (eds D. Dunon, C. R. Mackay, and B. A. Imhof) CD44: a multitude of isoforms with diverse functions

The CD44 transmembrane glycoprotein of 90 kDa has been known for more than 10 years under such diverse designations as lymphocyte homing receptor (gp90Hermes), phagocytic glycoprotein (Pgp-1), extracellular matrix receptor III (ECMRIII) and hyaluronate receptor (H-CAM) (see reviews by Haynes et al. 1989 and 1991). Studies with monoclonal antibodies revealed similarity, and most likely identity, among these molecules (Omary etal. 1988; Gallatin et al. 1989; Picker et al. 1989; Aruffo et al. 1990; Miyake et al. 1990; Culty et al. 1990). When the human, baboon and murine cDNA sequences were established identity was confirmed. However, the cDNA sequence codes only for about 360 amino acids, revealing a 37 kDa protein core (Stamenkovic et al. 1989; Goldstein et al. 1989; Idzerda et al. 1989; Nottenburg et al. 1989; Zhou et al. 1989; Wolffe et al. 1990). This protein core is highly glycosylated by N- and O-linked sugars to yield a 85–90 kDa form and is sometimes additionally linked to chondroitin sulfate side chains to produce a 180–220 kDa form (Jalkanen et al. 1988; Stamenkovic et al. 1989).