Requirements for hyaluronic acid binding by CD44: a role for the cytoplasmic domain and activation by antibody.

Abstract

SummaryThe CD44-negative T lymphoma AKR1 (CD44.2 genotype) was transfected with a CD44.1 cDNA. The intact eDNA conferred on the transfected cells the ability to bind hyaluronic acid (HA) both from solution and immobilized on culture plates. It also conferred a CD44-dependent and hyaluronidase-sensitive increase in adhesion to a lymph node endothelial cell line. A mutant cDNA which codes for a CD44 molecule lacking most of the cytoplasmic domain of CD44 was also transfected into AKR1, and cell sorting was used to sdect transfectants expressing levels of cell surface CD44 expression comparable with the line transfected with the wild-type CD44 cDNA. The cells transfected with the mutant construct bound fluoresceinated HA from solution very poorly, but did adhere to immobilized HA, though less well than ceils transfected with the wild-type construct. This result indicates that the cytoplasmic domain of CD44 is necessary for binding of HA from solution but is not required for binding to immobilized HA, although it may contribute to adhesion following ligand recognition. A monoclonal antibody (mAb), IILAWB 14, which reacts with CD44 on all CD44 + cells dramatically induced HA binding by some CD44 + cell lines that did not constitutively bind HA. The transfectant expressing a CD44 molecule with a truncated cytoplasmic domain could be induced by this antibody to bind fluoresceinated-HA from solution.' Splenic T cells did not bind fluoresceinated HA constitutively. In the presence of the IKAWB 14 mAb, virtually all CD44 + splenic T cells bound HA. Induction was immediate and occurred equally well at room temperature and at 4~ indicating that the new HA-binding activity was due to preexistent CD44 molecules. These results are compatible with an antibody-induced activation of CD44 by either a conformational change in the CD44 molecule or a change in the distribution of CD44 molecules on the cell surface.

Antibodies to CD44 enhance adhesion of normal CD34+ cells and acute myeloblastic but not lymphoblastic leukaemia cells to bone marrow stroma

“…Some monoclonal antibodies to CD44 have been reported to induce adhesion to hyaluronic acid (Lesley et al, 1992). However, K562 cells do not bind to hyaluronic acid either spontaneously or in the presence of NIH44-1 (data not shown).…”

“…It remains possible that small variations in the core protein, or type and/or location of carbohydrate side chains may be important. Alternatively, the manner in which CD44 is anchored into the cytoskeleton may be important (Lesley et al, 1992). However, in addition to glycosylation it is also recognized that the cell type per se can determine CD44 adhesive responses (van der Voort et al, 1995).…”

CD44 Suppresses TLR-Mediated Inflammation

“…To assess the role of the cytoplasmic domain of CD44 in TLR signaling, we examined the transcriptional activation of NF-B in MEFs transfected with a truncated CD44 mutant pCIneoCD44Ed (deletion of aa 291-361), which behaves as a dominant-negative molecule in the functioning of CD44 (31,32). Transfection of the CD44Ed (deletion of aa 291-361) mutant into CD44ϩ/ϩ MEFs enhanced the activation of NF-B while transfection of full-length CD44E into CD44Ϫ/Ϫ MEFs reduced both the zymosan and LPS-induced activations of NF-B (Fig.…”

CD44: A Multitude of Isoforms with Diverse Functions

“…Although almost all lymphoid cells express CD44S, only a minority has an affinity for HA (Lesley et al, 1992). The affinity of CD44 for HA may be influenced by conformational changes, interaction with neighbouring cell surface molecules to form heterodimers, by homodimerization or the formation of larger complexes.…”

“…The affinity of CD44 for HA may be influenced by conformational changes, interaction with neighbouring cell surface molecules to form heterodimers, by homodimerization or the formation of larger complexes. Activation of lymphocytes leads to an induction of HA binding (Murakami et al, 1990 and1991;Lesley et al, 1992).…”