Biology subjects

Sodhi, A.

Publications and source records attributed to Sodhi, A..

3 recordsLinked to original sources

bioRxiv2026

An epigenetic bifunctional that toggles between transactivation and repression

The targeted modulation of gene expression with bifunctional small molecules enables the precise control of cellular and biological processes. To screen for ligands that could be used to induce gene expression, we conjugated the high affinity FKBP(F36V) binder, AP1867, to known high-affinity binders of activating epigenetic machinery. We tested these bifunctionals in a FKBP(F36V)-tagged transcription factor reporter system and found bifunctional induced transactivation is relatively common, being observed for bifunctionals with BET ligand JQ1, p300/CBP ligand GNE-781, CDK9 ligand SNS-032, and BRD9 ligand iBRD9. aTAG-2 (mAP1867-C8-GNE781) was identified as the strongest and most potent transactivator, possessing single-digit nanomolar activity. When tested in models where oncogenic RNA binding protein-transcription factor fusion proteins have been FKBP(F36V)-tagged, we unexpectedly observed rapid collapse of the fusion transcriptional program. In a tagged Ewing sarcoma model, aTAG-2 exhibits at least three distinct mechanisms of action: i) RIPTAC mediated p300/CBP inhibition, ii) ubiquitination- and ternary complex-dependent EWS/FLI degradation, and iii) replacement of p300 with CBP at EWS/FLI bound chromatin loci. Together, these data establish bifunctionals targeting p300/CBP that toggle between a program of ultra-potent transactivation and repression depending on cellular context. Overall demonstrating that induced proximity with a given ligand does not encode a fixed functional outcome.

biochemistry↗

bioRxiv2025

A conformationally heterogeneous bending pivot enables bent-to-straight transition in the central helix of mycobacterial FtsZ

Conformational changes in the central helix at the inter-domain cleft of bacterial treadmilling motor protein FtsZ are coupled to polymerization. Central helix of mycobacterial FtsZ interconverts between a bent and a straight form, with an unknown mechanism. We probed the mechanism of this conformational switching in the central helix of mycobacterial FtsZ using multi-temperature synchrotron crystallography at 20 {o}C, 30 {o}C, 37 {o}C and -173 {o}C temperatures. A comparison of the resultant crystal structures of FtsZ revealed altered conformations at the bending pivot of the bent central helix inside the inter-domain cleft. Further, ensemble modeling of FtsZ structure shows that this bending pivot is labile at near-physiological temperatures. Conformational fluctuations in this pivot region resulted in breakage of regular alpha helical hydrogen bonds that likely made the central helix easily bendable. These fluctuations are largely arrested in the straightened form of the central helix in comparison to the bent form. To summarize, multi-temperature crystallography combined with ensemble modeling suggest that conformational heterogeneity and associated perturbations of helix-forming interactions in the bending pivot can trigger bent-to-straight conformational transition in the central helix of mycobacterial FtsZ. This work demonstrates the effectiveness of multi-temperature crystallography in delineating the mechanisms of conformational changes in protein machines.

biophysics↗

bioRxiv2023

The AKT2/SIRT5/TFEB pathway as a potential therapeutic target in atrophic AMD

Introductory paragraphAge-related macular degeneration (AMD), the leading cause of geriatric blindness, is a multi-factorial disease with retinal-pigmented epithelial (RPE) cell dysfunction as a central pathogenic driver. With RPE degeneration, lysosomal function is a core process that is disrupted. Transcription factors EB/E3 (TFEB/E3) tightly control lysosomal function; their disruption can cause aging disorders, such as AMD. Here, we show that induced pluripotent stem cells (iPSC)-derived RPE cells with the complement factor H variant [CFH (Y402H)] have increased AKT2, which impairs TFEB/TFE3 nuclear translocation and lysosomal function. Increased AKT2 can inhibit PGC1, which downregulates SIRT5, an AKT2 binding partner. SIRT5 and AKT2 co-regulate each other, thereby modulating TFEB-dependent lysosomal function in the RPE. Failure of the AKT2/SIRT5/TFEB pathway in the RPE induced abnormalities in the autophagy-lysosome cellular axis by upregulating secretory autophagy, thereby releasing a plethora of factors that likely contribute to drusen formation, a hallmark of AMD. Finally, overexpressing AKT2 in RPE cells in mice led to an AMD-like phenotype. Thus, targeting the AKT2/SIRT5/TFEB pathway could be a potential therapy for atrophic AMD.

cell biology↗