A single amino acid substitution converts a transmembrane protein activator of the platelet-derived growth factor ? receptor into an inhibitor.

ABSTRACT: Receptors for PDGF play an important role in cell proliferation and migration and have been implicated in certain cancers. The 44-amino acid E5 protein of bovine papillomavirus binds to and activates the PDGF? receptor (PDGF?R), resulting in oncogenic transformation of cultured fibroblasts. Previously, we isolated an artificial 36-amino acid transmembrane protein, pTM36-4, which transforms cells because of its ability to activate the PDGF?R despite limited sequence similarity to E5. Here, we demonstrated complex formation between the PDGF?R and three pTM36-4 mutants: T21E, T21Q, and T21N. T21Q retained wild type transforming activity and activated the PDGF?R in a ligand-independent manner as a consequence of binding to the transmembrane domain of the PDGF?R, but T21E and T21N were severely defective. In fact, T21N substantially inhibited E5-induced PDGF?R activation and transformation in both mouse and human fibroblasts. T21N did not prevent E5 from binding to the receptor, and genetic evidence suggested that T21N and E5 bind to nonidentical sites in the transmembrane domain of the receptor. T21N also inhibited transformation and PDGF?R activation induced by v-Sis, a viral homologue of PDGF-BB, as well as PDGF-induced mitogenesis and signaling by preventing phosphorylation of the PDGF?R at particular tyrosine residues. These results demonstrated that T21N acts as a novel inhibitor of the PDGF?R and validated a new strategy for designing highly specific short transmembrane protein inhibitors of growth factor receptors and possibly other transmembrane proteins.

SUBMITTER: Petti LM 

PROVIDER: S-EPMC3779723 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature