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J Biol Chem. 2017 Apr 28;292(17):7173-7188. doi: 10.1074/jbc.M116.768754. Epub 2017 Feb 22.

An engineered transforming growth factor β (TGF-β) monomer that functions as a dominant negative to block TGF-β signaling.

Author information

1
the Departments of Biochemistry and Structural Biology and.
2
Cell Systems and Anatomy.
3
From the Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260.
4
the National Research Council, Human Health Therapeutics Portfolio, Montréal, Quebec H4P 2R2, Canada.
5
Center for Innovative Drug Discovery, University of Texas Health Science Center, San Antonio, Texas 78229-3900, and.
6
From the Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, ahinck@pitt.edu.

Abstract

The transforming growth factor β isoforms, TGF-β1, -β2, and -β3, are small secreted homodimeric signaling proteins with essential roles in regulating the adaptive immune system and maintaining the extracellular matrix. However, dysregulation of the TGF-β pathway is responsible for promoting the progression of several human diseases, including cancer and fibrosis. Despite the known importance of TGF-βs in promoting disease progression, no inhibitors have been approved for use in humans. Herein, we describe an engineered TGF-β monomer, lacking the heel helix, a structural motif essential for binding the TGF-β type I receptor (TβRI) but dispensable for binding the other receptor required for TGF-β signaling, the TGF-β type II receptor (TβRII), as an alternative therapeutic modality for blocking TGF-β signaling in humans. As shown through binding studies and crystallography, the engineered monomer retained the same overall structure of native TGF-β monomers and bound TβRII in an identical manner. Cell-based luciferase assays showed that the engineered monomer functioned as a dominant negative to inhibit TGF-β signaling with a Ki of 20-70 nm Investigation of the mechanism showed that the high affinity of the engineered monomer for TβRII, coupled with its reduced ability to non-covalently dimerize and its inability to bind and recruit TβRI, enabled it to bind endogenous TβRII but prevented it from binding and recruiting TβRI to form a signaling complex. Such engineered monomers provide a new avenue to probe and manipulate TGF-β signaling and may inform similar modifications of other TGF-β family members.

KEYWORDS:

cancer; cell signaling; dominant negative; fibrosis; inhibitor; protein engineering; transforming growth factor beta (TGF-B)

PMID:
28228478
PMCID:
PMC5409485
DOI:
10.1074/jbc.M116.768754
[Indexed for MEDLINE]
Free PMC Article

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