CD44 can be activated to function as an hyaluronic acid receptor in normal murine T cells.
The hyaluronic acid (HA)-binding function of CD44 expressed on the cell surface of normal hematopoietic cells has been studied by assaying binding of fluoresceinated hyaluronic acid (F1-HA) and adhesion to immobilized HA. As has been observed previously, normal hematopoietic cells from bone marrow and spleen do not constitutively bind HA. A CD44-specific monoclonal antibody, IRAWB 14, which has been shown to rapidly induce HA binding in some CD44+ cell lines, was used to activate the HA-binding function of CD44 in these normal cells. Only splenic T cells were activated by the IRAWB 14 antibody to bind F1-HA. Upon activation, F1-HA binding correlated with the level of CD44 expression. Activation of HA binding allowed splenic T cells to adhere to HA immobilized on plastic and to an endothelial cell line in an HA-dependent manner. BALB/c and AKR/J splenic T cells differ in their level of CD44 expression, and this correlated with differences in their ability to bind HA upon antibody activation. The minor subpopulation of MEL-14- T cells were among the brightest F1-HA-staining cells. We propose, on the basis of these and other results, that there are three states of CD44 function with respect to HA binding: (a) a non-activatable, resting state, which cannot be rapidly activated to bind HA, as seen in most hematopoietic cells; (b) an activatable state, which can be rapidly converted to HA-binding function, in this case by the IRAWB 14 antibody, illustrated by T cells as shown here; and (c) a constitutively active state, which can bind HA without antibody activation, seen in some cell lines.
Lesley
J
J
Department of Cancer Biology, Salk Institute, San Diego, CA 92186-5800.
Hyman
R
R
D000818:Animals; D002448:Cell Adhesion; D018960:Hyaluronan Receptors; D006820:Hyaluronic Acid / Q000378:metabolism*; D051379:Mice; D008806:Mice, Inbred AKR; D008807:Mice, Inbred BALB C; D011956:Receptors, Cell Surface / Q000032:analysis*; D016201:Receptors, Lymphocyte Homing / Q000032:analysis*; D013601:T-Lymphocytes / Q000378:metabolism*
D018960:Hyaluronan Receptors; D011956:Receptors, Cell Surface; D016201:Receptors, Lymphocyte Homing; D006820:Hyaluronic Acid