To study cellular and subcellular localization of TIMP-1, we constructed a cDNA which would express a chimeric protein, TIMP-1-EGFP, having the enhanced green fluorescent protein of the jelly fish Aequorea victoria fused to the carboxyl-terminus of TIMP-1. Chinese Hamster Ovary (CHO) cells were stably transfected with the TIMP-1-EGFP expressing plasmid. The secreted chimera was processed through the endoplasmic reticulum and Golgi, as was shown by fluorescent confocal microscopy after incubations at temperatures which block processing at the intermediate compartment and the trans-Golgi network. 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 preferentially bind to and be taken up by malignant breast epithelial cells and that TIMP-1 may play a yet unidentified role in nuclear functions.
Copyright 1999 Academic Press.