Biological activity differences between TGF-β1 and TGF-β3 correlate with differences in the rigidity and arrangement of their component monomers

Tao Huang, Seth L. Schor, Andrew P. Hinck

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    20 Citations (Scopus)
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    Abstract

    TGF-ß1, -ß2, and -ß3 are small, secreted
    signaling proteins. They share 71-80% sequence identity
    and signal through the same receptors, yet the isoform-specific
    null mice have distinctive phenotypes and are inviable. The
    replacement of the coding sequence of TGF-ß1 with TGF-ß3
    and TGF-ß3 with TGF-ß1 led to only partial rescue of the
    mutant phenotypes, suggesting that intrinsic differences
    between them contribute to the requirement of each in vivo.
    Here, we investigated whether the previously reported
    differences in the flexibility of the interfacial helix and
    arrangement of monomers was responsible for the differences in activity by generating two chimeric proteins in which residues
    54-75 in the homodimer interface were swapped. Structural analysis of these using NMR and functional analysis using a dermal
    fibroblast migration assay showed that swapping the interfacial region swapped both the conformational preferences and activity.
    Conformational and activity differences were also observed between TGF-ß3 and a variant with four helix-stabilizing residues
    from TGF-ß1, suggesting that the observed changes were due to increased helical stability and the altered conformation, as
    proposed. Surface plasmon resonance analysis showed that TGF-ß1, TGF-ß3, and variants bound the type II signaling receptor,
    TßRII, nearly identically, but had small differences in the dissociation rate constant for recruitment of the type I signaling
    receptor, TßRI. However, the latter did not correlate with conformational preference or activity. Hence, the difference in activity
    arises from differences in their conformations, not their manner of receptor binding, suggesting that a matrix protein that
    differentially binds them might determine their distinct activities.
    Tr
    Original languageEnglish
    Pages (from-to)5737-5749
    Number of pages13
    JournalBiochemistry
    Volume53
    Issue number36
    Early online date25 Aug 2014
    DOIs
    Publication statusPublished - 16 Sep 2014

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