Biology subjects

Ravi, T.

Publications and source records attributed to Ravi, T..

4 recordsLinked to original sources

bioRxiv2026

AT1R-Selective Negative Allosteric Modulator Targeting the Epitope for Pathogenic Autoantibody Activation

A major therapeutic strategy for managing cardiovascular and renal diseases is the use of angiotensin receptor blockers (ARBs). These drugs block both pathogenic and physiological signaling by the angiotensin II type 1 receptor (AT1R) by preventing angiotensin II (AngII) binding to orthosteric pocket in transmembrane portion of AT1R. However, in many autoimmune diseases, AT1R activation is chronically driven by pathogenic autoantibody binding to a distinct extracellular surface located allosteric site. Currently, there are no allosteric inhibitors of AT1R available to mechanistically prevent the autoantibodies and preserve the orthosteric hormonal functions of AngII. Here, we report the structure-guided hit-to-lead optimization of TP1, a first-in-class AT1R allosteric chemotype and negative allosteric modulator (NAM) with improved potency and drug-like properties. Computational docking and site-directed mutagenesis identified a TP1 binding mode that is distinct from the orthosteric-site binding of ARBs and AngII. Synthetically pure TP1 significantly reduced the capacity of AT1R to bind AngII without affecting AngII binding to AT2R, demonstrating an AT1R selective effect. TP1 reduced AngII-induced calcium signaling and migration in AT1R-expressing cells, arterial contraction, and increases in blood pressure in AngII-infused mice, demonstrating its activity as a NAM. Crucially, TP1 blocked binding of pathogenic autoantibodies to AT1R-expressing cells from the serum of patients with preeclampsia and dilated cardiomyopathy, a function distinct from ARBs. Together, these findings establish TP1 as a proof-of-concept, AT1R-selective NAM chemotype with therapeutic potential for AT1R autoantibody-driven conditions such as preeclampsia, where ARBs are strictly contraindicated. Developing AT1R-targeted NAM antihypertensive drugs may offer therapeutic advantages over ARBs and expand the pharmacological toolkit for this important CVD receptor. Key words: AT1R, AngII, AT1R-AAb, NAM, Allosteric ligand, GPCR, blood pressure, pharmacokinetics, antihypertensives

pharmacology and toxicology↗

bioRxiv2026

A shark variable new antigen receptor recognizes an occluded epitope of fibroblast activation protein

Variable new antigen receptors (VNARs) are the smallest naturally occurring antibody binding domains. Their size allows VNARs to access sterically restricted epitopes that are inaccessible to conventional antibodies. We recently identified a suite of VNARs that target fibroblast activation protein (FAP), a stromal serine protease indicative of extracellular matrix remodeling. The presence of FAP on the surface of cancer-associated fibroblasts (CAFs) that promote immunosuppression has made FAP a compelling therapeutic target for cancer therapy. Although antibodies targeting FAP have been developed, there is a paucity of information on how biologics engage FAP. Here, we used single-particle cryogenic electron microscopy (cryo-EM) to compare FAP recognition of three antibody architectures: a shark-derived VNAR, variable heavy (VH) and light domains (VL) of a humanized Immunoglobulin G (IgG), and a camelid-derived VHH. The humanized VH-VL domains and camelid VHH both target a solvent-exposed {beta}-propeller domain, whereas the VNAR binds a highly conserved, topologically recessed epitope at the FAP dimer interface. Radical-footprinting mass spectrometry (MS) further mapped two additional immune-derived VNARs to distinct FAP surfaces outside the shared {beta}-propeller epitope. These findings demonstrate how unique VNAR architecture can expand access to underexplored FAP surfaces and establish a structural framework for rational multiepitope targeting strategies.

biochemistry↗

bioRxiv2025

Interictal activity fluctuations follow rather than precede seizures on multiple time scales in a mouse model of focal cortical dysplasia

The unpredictability of seizure occurrence is a major debilitating factor for people with epilepsy. A seizure forecasting system would greatly improve their quality of life. Successful seizure forecasting necessitates a comprehensive understanding of the factors influencing seizure timing at multiple temporal scales. In this study, we investigated multiscale properties of interictal epileptiform discharges (IEDs) and seizure parameters in a highly realistic mouse model of focal cortical dysplasia-related epilepsy. We analyzed the properties evolution at four timescales, ranging from epilepsy progression and seizure clusters to circadian and peri-ictal changes. We discovered that the FCD-related epilepsy syndrome was progressive in terms of interictal activity rate and seizure characteristics. Sixty percent of seizures occurred in clusters. During the clusters, the seizure duration, seizure power, and IED rate were increasing. Circadian rhythm influenced seizure occurrence with the peak seizure probability at 4 p.m. under a standard 12/12 light dark cycle with lights-on at 6 a.m. Peri-ictal analysis revealed no significant change in IED rate preceding individual seizures; however, a consistent two-peak pattern of IED elevation was observed following seizures. Specifically, an initial peak in IED rate emerged 5-10 minutes post-seizure, returning to baseline within two hours, followed by a secondary peak 6-12 hours later, which again subsided to baseline levels in 24-48 hours. This pattern could be fitted with a sum of three exponentials. Using the three-exponential pattern, we simulated IED rate fluctuations in each animal. The smoothed simulated IED rates showed good agreement with the smoothed real recorded IED rates, suggesting that the cumulative effect of post-ictal IED patterns can account for long-term fluctuations in IED rate. Our results indicate that, in our model of FCD-related epilepsy, consistent IED rate fluctuations follow rather than precede individual seizures. Therefore, fluctuations in IED rate can be viewed as a reflection of cyclic seizure occurrence. This implies that either IED rate fluctuations or accurate seizure records may be equally valuable for seizure risk forecasting. HighlightsO_LIFCD-related epilepsy model displays a progressive nature and fluctuations between high and low seizure risk. C_LIO_LISeizures occur with higher probability in the day time which corresponds to sleep-related seizures commonly occurring in human patients with FCD. C_LIO_LIIED rate increases significantly after seizures, indicating a postictal effect rather than a preictal one, with the post-ictal phase displaying a two-peak pattern of fast and slow IED rate increase. C_LIO_LILong-term changes in the IED rate could be attributed to the time-dependent cumulative effect of the two-peak seizure-related increase in IED rate. C_LI

neuroscience↗

bioRxiv2025

Microbial metabolite 4-ethylphenylsulfate (4EPS) interacts with AT1R, reduces blood pressure and outcome of AngII-induced aortic aneurysm

BACKGROUNDPlasma accumulation of the gut microbial metabolite, 4-ethylphenylsulfate (4EPS), produced from dietary protein aromatic amino acids has been observed in correlative and associative studies of cardiovascular, renal, metabolic and neurological diseases. 4EPS level increases upon AngII infusion in mice. How 4EPS alters host physiology to contribute to progression of any disease state is currently unknown. METHODSTo test the hypothesis that 4EPS interferes with angiotensin binding to AT1R, we used multiple approaches: AT1R pharmacology, cell-signaling, ex vivo vascular contraction and a mouse model of angiotensin-induced aortic aneurysm (AA) disease. ApoE-null mice were fed high-fat diet and infused with AngII, or co-infused with 4EPS and Olmesartan. BP was recorded. At the end of infusion, aortas were assessed for severity of AA, contractile response and histopathology. To evaluate signaling associated with different AA outcomes plasma proteomics analysis was done. RESULTSIn vitro, 4EPS reduced the binding of angiotensin and Candesartan to AT1R and calcium signaling. Ex vivo, 4EPS decreased vasomotor response of the aorta to AngII. In vivo, 4EPS inhibited AngII-mediated increase of BP and reduced mortality from AA. Abdominal aorta remodeling in 4EPS+AngII co-infused mice showed an increase of elastin area and reduced thickening of intimal/medial layers. Plasma proteome analysis indicated significant change in actin-cytoskeletal signaling associated with reduced ERK1/2 and Filamin-A activation, and cell motility. CONCLUSIONSBenign antagonism of AT1R by 4EPS involves direct interaction with AT1R. Molecular mechanisms of 4EPS responsible for reduced AA associated mortality in mice are distinct from those of AT1R blocker, Olmesartan. GRAPHIC ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=123 HEIGHT=200 SRC="FIGDIR/small/635371v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1a33049org.highwire.dtl.DTLVardef@b73071org.highwire.dtl.DTLVardef@cd5557org.highwire.dtl.DTLVardef@9dc63e_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗