Transforming growth factor beta 1 positively regulates its own expression in normal and transformed cells

Abstract

Transforming growth factor beta 1 (TGF-beta 1) regulates the growth, differentiation, or function of nearly all cell types. We now report that TGF-beta 1 increases steady-state levels of its own message in six different normal and transformed cells in culture. Accumulation of TGF-beta 1 mRNA can be detected by Northern blot analysis within 3 h of addition of the peptide to cells, and enhanced message levels persist as long as TGF-beta 1 is present in the culture medium. This autoinduction is half-maximal at approximately 10 PM TGF-beta 1, and maximal stimulation corresponds to a 2-3-fold increase in transcript levels. In normal rat kidney cells, the rise in TGF-beta 1 mRNA is actinomycin D-sensitive and is accompanied by a parallel (approximately 3-fold) increase in secretion of TGF-beta 1 protein in the culture medium of treated cells, as detected by immunoprecipitation of biosynthetically labeled 35S-labeled TGF-beta 1 using specific anti-TGF-beta 1 antibodies. Treatment of normal rat kidney cells with either epidermal growth factor or platelet-derived growth factor also results in an increase in TGF-beta 1 mRNA (2-3-fold), although epidermal growth factor and TGF-beta 1 appear to act via distinct mechanisms since their combined effects are greater than additive.