BINDING OF CELL-SURFACE EXPRESSED CD44 TO HYALURONATE IS DEPENDENT ONSPLICING AND CELL-TYPE

CD44 is a major cell-surface receptor for hyaluronate (HA). By alterna tive RNA-splicing a large number of CD44 variants are generated. To ex plore the role of CD44 splicing in the regulation of cell binding to H A, three different isoforms of CD44 were transfected in the CD44 negat ive B-cell lymphoma line Namalwa and in the fibroblastoid cell line CO S7. We observed that whereas the standard form of CD44 (CD44s) mediate d adhesion of Namalwa to HA, Namalwa transfected with CD44v3-10 or CD4 4v8-10 was unable to bind to either immobilized or soluble HA. After s timulation of CD44 with an activating anti-CD44 mAb or with phorbol es ter, the binding of CD44s to HA was 5- to 10-fold higher than that of the other two isoforms. By contrast, COS7 cells transfected with CD44s , CD44v8-v10, or CD44v3-v10 bound equally effectively to HA. Hence, in addition to alternative splicing, cell type determines CD44 bindnig t o HA. (C) 1995 Academic Press, Inc.