DOMINANT-NEGATIVE ABROGATION OF CONNEXIN-MEDIATED CELL-GROWTH CONTROLBY MUTANT CONNEXIN GENES

Connexin genes exert negative growth control when transfected into var ious types of tumor cell lines, We previously demonstrated that connex in 26 (Cx26) suppresses in vitro and in vivo growth of HeLa cells, In this study, we have examined whether certain Cx26 mutants can abrogate cell growth control and the gap junctional intercellular communicatio n (GJIC) capacity of such Cx26-transfected HeLa cells, For this purpos e, we transfected three mutated Cx26 genes (C60F, P87L and R143W) into HeLa cells already containing the wild-type Cx26 gene, which are GJIC -competent and non-tumorigenic. Transfection of P87L and R143W mutants enhanced the tumorigenicity of the HeLa Cx26 cells in nude mice witho ut any change in GJIC capacity, On the other hand, transfection of the C60F mutant reduced the GJIC capacity of HeLa Cx26 cells without affe cting their growth in vivo. Immunostaining studies demonstrated that t he Cx26 proteins were localized mainly at cell-cell contact areas in t he Hel,a Cx26 cells both before and after transfection of mutated Cx26 genes, These results suggest that certain mutant Cx26 proteins exert a dominant-negative effect on Cx26-regulated growth of HeLa cells and that such effects may be independent of the effect on GJIC ability, It is proposed that wild-type and mutant Cx26 proteins produce heteromer ic connexons and that such heteromeric connexons may exert different e ffects on growth control from those of homomeric connexons.