Human keratinocytes express EMMPRIN, an extracellular matrix metalloproteinase inducer.
Increased levels of matrix metalloproteinases are associated with tissue degradation and remodeling during tumor invasion and wound healing. In both processes, there is evidence that cell interactions between fibroblasts and tumor cells or keratinocytes lead to increases in metalloproteinase production. We have previously isolated and purified a tumor cell surface protein, EMMPRIN (extracellular matrix metalloproteinase inducer), which stimulates production of interstitial collagenase, gelatinase A, and stromelysin-1 by fibroblasts, and we have obtained cDNA clones that encode the EMMPRIN protein from LX-1 human lung carcinoma cells. In this study we report immunolocalization of EMMPRIN around the surface of human keratinocytes in vitro and in vivo, and isolation of cDNAs that encode the entire open reading frame for EMMPRIN from a human keratinocyte library. Comparison of the EMMPRIN cDNAs from normal human keratinocytes and LX-1 human tumor cells by nucleotide sequence analysis, expression of the recombinant proteins, and in vitro translation using the cDNAs from the two sources indicate that they express very similar forms of EMMPRIN. Native EMMPRIN isolated directly from extracts of keratinocytes, however, is slightly smaller in size and is present at a lower concentration compared with that from LX-1 tumor cells. These results establish the presence of EMMPRIN in the normal epidermis and raise the possibility of its involvement in regulation of matrix remodeling at the epidermal-dermal interface.