Interaction between CD44 and the repeat domain of ankyrin promotes hyaluronic acid-mediated ovarian tumor cell migration

The adhesion molecule, CD44, interacts with ankyrin within its cytoplasmic domain and binds to hyaluronic acid (HA) at its extracellular domain. In th is study, we focused on the functional domain in ankyrin tin particular, th e ankyrin repeat domain [ARD]) responsible for CD44 binding and its role in regulating HA-mediated ovarian tumor cell function. Using recombinant frag ments of ankyrin (e.g., ARD and subdomain 1 [S1, aa1-aa217], subdomain 2 [S 2, aa218-aa381], subdomain 3 [S3, aa382-aa612], and subdomain 4 [S4, aa613- aa834]) and in vitro binding assays, we determined that the S2 but not S1, S3, or S4 of ARD is the primary ankyrin binding region for CD44. Microinjec tion of antiglutathione S-transferase (GST)-tagged S2 or CST-tagged ARE fus ion protein into CD44-positive ovarian tumor cells (e.g., SKOV3 cell line) promotes ankyrin association with CD44 in plaque-like structures and membra ne projections. Additionally, we demonstrated that transfection of SKOV3 ce lls with S2cDNA or ARD cDNA results in an upregulation of HA-mediated tumor cell migration. Taken together, we believe that the S2 of the ARD plays a pivotal role in the direct binding to CD44 and promotes the cytoskeleton ac tivation required for HA-mediated function such as ovarian tumor cell migra tion, (C) 2000 Wiley-Liss, Inc.