Identification of the Thiol Isomerase-binding Peptide, Mastoparan, as a Novel Inhibitor of Shear-induced Transforming Growth Factor β1 (TGF-β1) Activation

• Published in: The Journal of biological chemistry 2013-04, Vol.288 (15), p.10628-10639
• Main Authors: Brophy, Teresa M., Coller, Barry S., Ahamed, Jasimuddin
• Format: Article
• Language: English
• Subjects: Blood Platelets - metabolism; Blood Proteins - metabolism; Cell Line; Clusterin - metabolism; Disulfides - metabolism; Female; Genomics and Proteomics; Humans; Intercellular Signaling Peptides and Proteins; Latent TGF-beta Binding Proteins - metabolism; Male; Peptides - pharmacology; Platelets; Protein Binding - drug effects; Protein Disulfide Isomerases; Protein Disulfide-Isomerases - antagonists & inhibitors; Protein Disulfide-Isomerases - metabolism; Redox Regulation; Shear Stress; Thrombosis; Transforming Growth Factor Beta (TGFbeta); Transforming Growth Factor beta1 - metabolism; von Willebrand Factor - metabolism; Wasp Venoms - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.439034

TGF-β1 is a disulfide-bonded homodimeric protein produced by platelets and other cells that plays a role in many physiologic and pathologic processes. TGF-β1 is secreted as an inactive large latent complex (LLC) comprised of TGF-β1, latency-associated peptide, and latent TGF-β binding protein 1. We previously demonstrated that shear force can activate LLC and that thiol-disulfide exchange contributes to the process. We have now investigated the role of thiol isomerases in the activation of LLC in platelet releasates (PR) and recombinant LLC. The wasp venom peptide mastoparan, which inhibits the chaperone activity of PDI, inhibited stirring- and shear-induced activation of latent TGF-β1 by 90 and 75% respectively. To identify the proteins that bind to mastoparan either directly or indirectly, PR were chromatographed on a mastoparan affinity column. Latent TGF-β binding protein 1, latency-associated peptide, TGF-β1, clusterin, von Willebrand factor, multimerin-1, protein disulfide isomerase (PDI), ERp5, ERp57, and ERp72 eluted specifically from the column. Anti-PDI RL90 attenuated the inhibitory effect of mastoparan on LLC activation. Furthermore, reduced PDI inhibited activation of PR LLC, whereas oxidized PDI had no effect. We conclude that thiol isomerases and thiol-disulfide exchange contribute to TGF-β1 activation and identify a number of molecules that may participate in the process. Background: We previously demonstrated that shear-induced TGF-β1 activation involves thiol-disulfide exchange. Results: The thiol isomerase binding peptide mastoparan and protein disulfide isomerase inhibit shear-induced TGF-β1 activation. Conclusion: Thiol isomerase(s) play a role in shear-induced TGF-β1 activation mediated by thiol-disulfide exchange. Significance: Shear-induced activation of TGF-β1 is a novel mechanism that involves thiol isomerase-mediated thiol-disulfide exchange.