Tissue inhibitor of metalloproteinases-1 (TIMP-1) binds to the cell surface and translocates to the nucleus of human MCF-7 breast carcinoma cells

To study cellular and subcellular localization of TIMP-1, we constructed a cDNA which would express a chimeric protein, TIMP-1-EGFP, having the enhanc ed green fluorescent protein of the jelly fish Aequorea victoria fused to t he carboxyl-terminus of TIMP-1, Chinese Hamster Ovary (CHO) cells were stab ly transfected with the TIRIPP-1-EGFP expressing plasmid. The secreted chim era was processed through the endoplasmic reticulum and Gels, as was shown by fluorescent confocal microscopy after incubations at temperatures which block processing at the intermediate compartment and the trans-Golgi networ k. In a co-culture system, secreted TIMP-1-EGFP could be visualized binding to the surface of MCF-7 breast carcinoma cells but not non-neoplastic HBL- 100 breast epithelial cells. TIMP-1-EGFP localized to the nucleus of MCF-7 cells after 72 hrs in co-culture. These findings suggest that TIMP-1 may pr eferentially bind to and be taken up by malignant breast epithelial cells a nd that TGIMP-1 may play a yet unidentified role in nuclear functions. (C) 1999 Academic Press.