Chuck, J. | Search bioRxiv

bioRxiv2026

Negative regulation of TH17-mediated inflammation by the nuclear receptor REV-ERBβ

TH17 cells play a central role in several human autoimmune diseases. We and others reported the nuclear receptor, REV-ERB, as a cell-intrinsic repressor of TH17-mediated pathogenicity. REV-ERB{beta}, REV-ERBs closely related family member, is thought to be functionally redundant to REV-ERB, which we sought to explore in TH17-mediated immunity. Our data indicate that deletion of REV-ERB{beta} enhances TH17-mediated pro-inflammatory cytokine expression and exacerbated disease in mouse models of multiple sclerosis and colitis. RNA-sequencing indicates REV-ERB{beta} and REV-ERB do not have similar transcriptional profiles. REV-ERB{beta} does not appear to regulate gene expression through interaction with the classic co-repressor NCoR1, which is in contrast to REV-ERB in TH17 cells, nor does it utilize heme, its known endogenous ligand for its repressive functions. Our results establish that while REV-ERB{beta} also acts as a negative regulator of TH17-cell function and pathogenicity, it does so in a manner that is non-redundant, independent, and unique to REV-ERB.

immunology↗

bioRxiv2024

A tethering mechanism underlies Pin1-catalyzed proline cis-trans isomerization at a noncanonical site

The prolyl isomerase Pin1 catalyzes the cis-trans isomerization of proline peptide bonds, a noncovalent post-translational modification that influences cellular and molecular processes, including protein-protein interactions. Pin1 is a two-domain enzyme containing a WW domain that recognizes phosphorylated serine/threonine-proline (pS/pT-P) canonical motifs and an enzymatic PPIase domain that catalyzes proline cis-trans isomerization of pS/pT-P motifs. Here, we show that Pin1 uses a tethering mechanism to bind and catalyze proline cis-trans isomerization of a noncanonical motif in the disordered N-terminal activation function-1 (AF-1) domain of the human nuclear receptor PPAR{gamma}. NMR reveals multiple Pin1 binding regions within the PPAR{gamma} AF-1, including a canonical motif (pS112-P113) that when phosphorylated by the kinase ERK2 binds the Pin1 WW domain with high affinity. NMR methods reveal that Pin1 also binds and accelerates cis-trans isomerization of a noncanonical motif containing a tryptophan-proline motif (W39-P40) previously shown to be involved in an interdomain interaction with the C-terminal ligand-binding domain (LBD) of PPAR{gamma}. Cellular transcription studies combined with mutagenesis and Pin1 inhibitor treatment reveal a functional role for Pin1-mediated acceleration of cis-trans isomerization of the PPAR{gamma} W39-P40 motif. Our data inform a refined model of the Pin1 catalytic mechanism where the WW domain can bind a canonical pS/T-P motif and tether Pin1 to a target, which enables the PPIase domain to exert catalytic cis-trans isomerization at a distal noncanonical site. SIGNIFICANCEPin1 is a multidomain prolyl isomerase enzyme that catalyzes the isomerization of proline peptide bonds, which naturally occur in cis and trans conformations that exchange on a timescale of seconds to minutes, allowing for switch-like effects on target protein structure and function. Previous mechanistic studies using small peptides derived from target substrates revealed Pin1 specifically binds to and displays enzymatic catalysis specificity for substrates containing a phosphorylated serine or threonine followed by a proline (pS/pT-P). Using a large substrate domain from the nuclear receptor peroxisome proliferator activated receptor gamma (PPAR{gamma}), we found that Pin1-catalyzed isomerization can occur at a noncanonical proline distal to a canonical pS/pT-P binding site. Our findings expand the understanding of Pin1-catalyzed enzymatic activities and target substrate functions.

biophysics↗