A human transforming growth factor-beta type II receptor that contains an insertion in the extracellular domain

In the signal transduction of transforming growth factor-beta (TGF-beta), the TGF-beta type II receptor (beta R-II) binds TGF-beta, presents the ligand to type I receptor, and forms a heterodimeric receptor complex that functions as an active signaling receptor. We isolated cDNA clones encoding an isoform of human beta R-II from vascular endothelial cells by RT-PCR. The deduced structure of the isoform designated as beta R-IIb contained a 25-amino acid residue inserted at the extracellular region. The insert exhibited 73% homology to a similar insertion found in a mouse beta R-II variant. beta R-IIb mRNA was ubiquitously expressed in all human cell lines examined. beta R-IIb as well as beta R-II stably expressed in beta RII-deficient DR26 cells acted as a functional receptor transducing signals from TGF-beta for growth inhibition and the transcriptional activation of the plasminogen activator inhibitor-1 promoter. These results indicated that the beta R-IIb expressed in mammalian cells functions indistinguishably from beta R-II. The potential function of beta R-IIb is discussed. (C) 1996 Academic Press, Inc.