IDENTIFICATION AND CHARACTERISATION OF TRANSFORMING GROWTH FACTOR BETA- REGULATED VASCULAR SMOOTH MUSCLE CELL GENES

Abstract

Transforming growth factor beta (TGFβ) is thought to play an important role in the development and/or progression of a number of vascular disorders through its numerous effects on vascular smooth muscle cells (VSMCs). In this study we sought to identify and characterize TGFβ-regulated VSMC genes using differential mRNA display (DD-RT-PCR) analysis of RNA isolated from TGFβ-stimulated cultured rat aortic VSMCs. Northern blot analysis was used to demonstrate that five of 19 differentially displayed bands identified represented VSMC transcripts differentially expressed by TGFβ. DNA sequencing revealed that three of these TGFβ regulated genes were novel whilst the remaining two were identified through homologies to known genes. One TGFβ upregulated transcript represented the protease cathepsin B. Since cathepsins may play a role in TGFβ activation, an enzyme-linked immunosorbent assay (ELISA) for active TGFβ1 was used to demonstrate an effect of cathepsin B on TGFβ1 activation in vitro using both recombinant and human serum platelet-derived latent TGFβ1 as substrate. These results suggest that induction of cathepsin B by TGFβ, and its ability to activate TGFβ1, may represent a mechanism whereby the autocrine action of TGFβ is facilitated through expression of a protein which can process its latent form.