Dominant Negative Mutants of Transforming Growth Factor-βl Inhibit the Secretion of Different Transforming Growth Factor-β Isoforms

Abstract

Transforming growth factor-β (TGF-β) is a secreted polypeptide factor that is thought to play a major role in the regulation of proliferation of many cell types and various differentiation processes. Several related isoforms have been structurally characterized, three of which, TGF-βl, -β2, and -β3, have been detected in mammalian cells and tissues. Each TGF-β form is a homodimer of a 112-amino-acid polypeptide which is encoded as a larger polypeptide precursor. We have introduced several mutations in the TGF-βl precursor domain, resulting in an inhibition of TGF-βl secretion. Coexpression of these mutants with wild-type TGF-βl, -β2, and -β3 results in a competitive and specific inhibition of the secretion of different TFG-β forms, indicating that these mutated versions act as dominant negative mutants for TGF-β secretion. Overexpression of dominant negative mutants can thus be used to abolish endogenous secretion of TGF-β and structurally related family members, both in vitro and in vivo, and to probe in this way the physiological functions of the members of the TGF-β superfamily.