TISSUE INHIBITOR OF METALLOPROTEINASES-3 (TIMP-3) IS AN EXTRACELLULARMATRIX-ASSOCIATED PROTEIN WITH A DISTINCTIVE PATTERN OF EXPRESSION INMOUSE CELLS AND TISSUES

We have isolated cDNA clones corresponding to a novel mouse metallopro teinase inhibitor. Five overlap ping cDNA clones contain most of the i nformation for a prominent 4.5-kilobase transcript that was detected i n RNA from mouse fibroblasts and adult tissues. Sequence analysis reve aled an open reading frame (ORF) for a protein of 212 amino acids that is 80% identical to chicken inhibitor of metalloproteinases-3 (ChIMP- 3). The 3'-untranslated sequence also showed remarkable conservation w ith the chicken gene. The ORF directed the expression of a 24-kDa prot ein in COS-1 cells that localized to the extracellular matrix (ECM). O n the basis of these similarities we propose to identify the new gene as murine tissue inhibitor of metalloproteinases-3 (TIMP-3). Mouse C3H 10T1/2 fibroblasts produced a 24- kDa metalloproteinase inhibitor tha t also localized to the ECM and was recognized by a polyclonal antibod y to ChIMP-3. Like TIMP-1, TIMP-3 was highly inducible in mouse C3H 10 T1/2 fibroblasts by phorbol ester (PMA), epidermal growth factor (EGF) , and transforming growth factor-beta 1, but nuclear run-on assays sho wed that the on/off transcription kinetics were faster for TIMP-3 than TIMP-1. A major difference in vitro was the stimulation of expression of TIMP-3 by dexamethasone which inhibits EGF- and PMA-induced TIMP-1 transcription. Also, TIMP-3 showed a distinctive pattern of expressio n in adult tissues with abundant transcripts detected in kidney, lung, and brain but only low levels detected in bone, a prominent location of TIMP-1 transcripts. We propose that TIMP-3 functions in a tissue sp ecific fashion as part of an acute response to remodeling stimuli.