DOMINANT AND NONDOMINANT NEGATIVE C-ERBA-BETA-1 RECEPTORS ASSOCIATED WITH THYROID-HORMONE RESISTANCE SYNDROMES AUGMENT 12-O-TETRADECANOYL-PHORBOL-13-ACETATE INDUCTION OF THE COLLAGENASE PROMOTER AND EXHIBIT DEFECTIVE 3,5,3'-TRIIODOTHYRONINE-MEDIATED REPRESSION

C-erbA receptors and v-erbA have been shown to functionally interact w ith 12-0-tetradecanoyl-phorbol-13-acetate (TPA)-inducible gene express ion. These proteins enhance trans-activation by c-jun, and the c-erbA receptors in the presence of thyroid hormone repress TPA and c-jun ind uction of transcription. Also, v-erbA can abrogate T3-mediated repress ion. We have examined how dominant negative (S and CL) and nondominant negative (G-H) receptors cloned from various patients with thyroid ho rmone resistance syndromes affect expression of the collagenase promot er induced with TPA. The CL receptor (ARG315HIS mutation) has a 2-fold reduction in T3-binding affinity compared with human c-erbAbeta1 wild -type (WT) receptor, whereas the G-H receptor (ARG311HIS) and S recept or (deletion, THR codon 332) have T3-binding affinities reduced by 100 -fold and greater than 100-fold, respectively. These mutant receptors were cotransfected with a collagenase promoter (-1200 to +63 base pair s) chloramphenicol acetyltransferase reporter gene (Col-CAT) into COS- 7 cells. Levels of CAT reporter gene expression after transient transf ection were determined in the presence or absence of 3-10 nM T3 and th e presence or absence of 100 nM TPA. Unoccupied CL receptor and G-H an d S receptors stimulated TPA-induced Col-CAT expression 1.5- to 9-fold . The CL receptor with thyroid hormone totally repressed TPA induction of the collagenase receptor. In the presence of thyroid hormone, the enhancing effects by S and G-H receptors on TPA-induced Col-CAT expres sion were unaffected and minimally diminished, respectively. However, when WT receptor was cotransfected with G-H or S receptors at 1:1 mola r ratios in the presence of T3, the transcriptional enhancement was co mpletely abrogated. Similar results with WT and mutant receptors on Co l-CAT activity were seen in cells transiently transfected with a const itutively active protein kinase C construct corresponding to the catal ytic domain of protein kinase C-alpha and grown in the absence of TPA. We conclude that human mutant c-erbAbeta1 receptors, dominant and non dominant negative, have functional properties similar to v-erbA in ter ms of effects on a TPA-inducible promoter. The transcriptional enhance ment of a TPA-inducible gene by the human mutants can be overcome by T 3-activated WT receptor. This effect of WT on mutant receptor function may diminish a potential neoplastic effect of the human mutant recept ors.