Biology subjects

Bohl, J.

Publications and source records attributed to Bohl, J..

3 recordsLinked to original sources

bioRxiv2026

Epigenetic Mechanisms Inhibit Smad7 and Contribute to Fibrosis in Crohn's Disease

Background & Aims: TGF-beta1 is a central regulator of profibrotic gene expression, extracellular matrix deposition, and the development of intestinal fibrosis in patients with fibrostenotic Crohns disease (CD). Unlike the increased expression of Smad7 in mucosal and lamina propria monocytes, where it impairs Treg function, mesenchymal cells from patients with fibrostenotic CD do not exhibit elevated Smad7 expression and instead display sustained TGF-beta1 signaling. We therefore sought to elucidate the mechanisms underlying the unexpected silencing of Smad7 in fibrostenotic CD. Methods: Subepithelial myofibroblasts (SEMFs) and muscularis smooth muscle cells were isolated from paired normal and affected ileal tissues obtained from the same patients with each Montreal phenotype of CD, as well as from non-CD controls. Gene expression, RNA-binding affinity, transcriptional activity, promoter methylation, protein levels, and the mechanisms that regulate Smad7 expression were evaluated in ex vivo tissues and primary cultured cells. MicroRNA-21 (miR-21) localization was assessed by RNAscope. miR-21-mediated suppression of Smad7 was investigated using antagomiR-21. Smad7 silencing through promoter hypermethylation was confirmed using 5-Azacytidine treatment and DNA methyltransferase 1 (DNMT1) knockdown. Smad7 lysine acetylation and Smurf1/2-mediated ubiquitination were examined using selective inhibitors and proximity ligation assays. Results: In SEMFs from patients with fibrostenotic CD, aberrant silencing of Smad7 resulted from DNMT1-dependent promoter hypermethylation and pSmad3-driven, miR-21-mediated degradation of Smad7 mRNA. In addition, Smurf1/2 promoted ubiquitination and proteasomal degradation of acetylated Smad7 protein. Inhibition of miR-21 with antagomiR-21 restored Smad7 expression and reduced TGF-beta 1-dependent profibrotic gene expression. Likewise, demethylation with 5-Azacytidine or knockdown of DNMT1 induced Smad7 promoter hypomethylation and restored Smad7 expression. Furthermore, modulation of the balance between p300 acetyltransferase and histone deacetylase 1 (HDAC1) stabilized Smad7 protein by protecting it from degradation. Conclusions: A distinctive pattern of epigenetic silencing and post-translational regulation of Smad7 was identified in patients with fibrostenotic CD. These mechanisms collectively promote unrestrained TGF-beta1 signaling by suppressing Smad7 expression and stability in SEMFs, thereby contributing to the development of intestinal fibrosis.

cell biology↗

bioRxiv2026

Non-fibrillar prion protein oligomers transmit structural information during early assembly

The prion paradigm is founded on the transmission of structural information from aggregated assemblies to soluble protein substrates, a process classically attributed to fibril-end-mediated templating. Whether non-fibrillar assemblies or transient oligomeric states can also participate in folding information transfer remains unclear. Here, using recombinant prion protein (PrP), rational mutagenesis, hetero-oligomerization assays, arrested reaction conditions, and single-particle atomic force microscopy coupled to infrared nano-spectroscopy (AFM-IR), we examine the earliest stages of PrP assembly from the perspective of folding information transmission. We show that polymerization-defective PrP variants can be incorporated into oligomeric assemblies through structural complementation, in which folding information supplied by wild-type PrP restores their assembly competence. Under arrested reaction conditions, transient polymerization-competent conformers further contribute to folding information transfer at subcritical concentrations. Domain-resolved analyses reveal a modular oligomeric architecture in which a {beta}-sheet-rich B domain constitutes the primary scaffold for folding information transfer. Preformed O1 oligomers then act as autonomous conformational templates that promote mutant incorporation and undergo hierarchical condensation through accretion of a structurally distinct E domain. Together, these findings demonstrate that non-fibrillar PrP oligomers and transient assembly intermediates can store and transmit folding information and may function as oligomer-based secondary nucleation platforms, expanding the conceptual framework of prion assembly beyond fibril-end elongation alone.

biochemistry↗

bioRxiv2023

The smallest infectious substructure encoding the prion strain structural determinant revealed by spontaneous dissociation of misfolded prion protein assemblies

It is commonly accepted that the prion replicative propensity and strain structural determinant (SSD) are encoded in the fold of PrPSc amyloid fibril assemblies. By exploring the quaternary structure dynamicity of several prion strains, we revealed that all mammalian prion assemblies exhibit the generic property of spontaneously generating two sets of discreet infectious tetrameric and dimeric species differing significantly by their specific infectivity. By using perturbation approaches such as dilution and ionic strength variation, we demonstrated that these two oligomeric species were highly dynamic and evolved differently in the presence of chaotropic agents. In general, our observations of seven different prion strains from three distinct species highlight the high dynamicity of PrPSc assemblies as a common and intrinsic property of mammalian prions. The existence of such small infectious PrPSc species harboring the SSD indicates that the prion infectivity and the SSD are not restricted only to the amyloid fold but can also be encoded in other alternative quaternary structures. Such diversity in the quaternary structure of prion assemblies tends to indicate that the structure of PrPSc can be divided into two independent folding domains: a domain encoding the strain structural determinant and a second domain whose fold determines the type of quaternary structure that could adopt PrPSc assemblies. HighlightsO_LIMammalian prion assemblies are highly dynamic C_LIO_LIPrion assemblies spontaneously disassemble into two infectious oligomers C_LIO_LIPrion infectivity is not exclusively encoded in the amyloid fibrils structure C_LIO_LITwo independent folding domains could structure Prion assemblies C_LI

biochemistry↗