ADAMs (a disintegrin and metalloproteases) mediate several important processes (e.g. tumor necrosis factor-α release, fertilization, and myoblast fusion). The ADAM disintegrin domains generally lack RGD motifs, and their receptors are virtually unknown. Here we show that integrin α9β1 specifically interacts with the recombinant ADAMs-12 and -15 disintegrin domains in an RGD-independent manner. We also show that interaction between ADAM-12 or -15 and α9β1 supports cell-cell interaction. Interestingly, the cation requirement and integrin activation status required for α9β1/ADAM-mediated cell adhesion and cell-cell interaction is similar to those required for known integrin-extracellular matrix interaction. These results are quite different from recent reports that ADAM-2/α6β1 interaction during sperm/egg fusion requires an integrin activation status distinct from that for extracellular matrix interaction. These results suggest that α9β1 may be a major receptor for ADAMs that lack RGD motifs, and that, considering a wide distribution of ADAMs and α9β1, this interaction may be of potential biological and pathological significance.
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