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Negative cooperativity regulates ligand activation of DIAPH1 and other diaphanous related formins

Theophall, G G; Premo, A; Reverdatto, S; Omojowolo, E; Nazarian, P; Burz, D S; Ramasamy, R; Schmidt, A M; Shekhtman, A
DIAPH1 is a member of the family of Diaphanous Related Formins (DRFs) implicated in cell migration and cytokinesis. DRFs are maintained in an autoinhibited state by the intramolecular association between diaphanous inhibitory (DID) and diaphanous autoregulatory (DAD) domains. Actin polymerization requires the binding of activated RhoA to the GTPase binding domain (GBD) of DIAPH1 and the dissociation of DAD. In the presence of excess RhoA, actin polymerization is only partially activated. Using monomeric domain constructs of DIAPH1, the sequential binding affinities of RhoA and DAD to GBD-DID were characterized. Binding of RhoA and DAD were negatively cooperative requiring a 100-fold greater concentration of DAD to achieve saturation when RhoA binding site was occupied. The unimolecular architecture of full length DIAPH1 establishes an effective concentration of DAD in the micromolar range, which is 100-fold larger than the intrinsic affinity of DAD for DID. The effective concentration is large enough to maintain DIAPH1 autoinhibition, yet small enough to permit partial activation of DIAPH1 after RhoA binding. By exploiting negative cooperativity, DIAPH1 maintains a reserve of inactivated molecules enabling gradual responses to cellular processes that require prolonged and sustained regulation. The proposed mechanism is extended to other DIAPH1 activating ligands and broadly applicable to all DRFs.
PMCID:12095592
PMID: 40399622
ISSN: 2399-3642
CID: 5853212

Mechanistic underpinnings of AGEs-RAGE via DIAPH1 in ischemic, diabetic, and failing hearts

Yepuri, Gautham; Hasan, Syed Nurul; Kumar, Vikas; Manigrasso, Michaele B; Theophall, Gregory; Shekhtman, Alexander; Schmidt, Ann Marie; Ramasamy, Ravichandran
Diabetes is a major risk factor for cardiovascular diseases. Patients with diabetes are at greater risk for morbidity and mortality post myocardial infarction. As the epidemic of diabetes continues at an alarming pace, identification of specific therapeutic interventions to protect diabetic patients from the devastating consequences of myocardial infarction is an urgent need. Advanced glycation end products (AGEs), the products of nonenzymatic glycation and oxidation of proteins and lipids, accumulate in the diabetic circulation and heart. The interaction of AGEs with its key receptor, receptor for AGE or RAGE, contributes to cardiac injury and dysfunction. The discovery that intracellular domain of RAGE binds to the formin, DIAPH1, and that DIAPH1 is essential for RAGE ligand-mediated signal transduction, unveiled the specific cellular means by which RAGE functions and highlights a new target for therapeutic interruption of pathological RAGE signaling during myocardial infarction. This review delves into intrinsic mechanisms by which AGE-RAGE axis via RAGE-DIAPH1 driven DIAPH1-Mitofusin2 (MFN2) interaction modulates pathogenic inter-organelle communications and opens opportunities for intensive studies to uncover the comprehensive mechanisms that drive injury-provoking actions from the intracellular space. This review illustrates the potential therapeutic cardioprotective benefits of antagonism of RAGE-DIAPH1interactions in the diabetic heart.
PMID: 40132210
ISSN: 1522-1539
CID: 5815232

Sex differences in murine MASH induced by a fructose-palmitate-cholesterol-enriched diet

Arivazhagan, Lakshmi; Delbare, Sofie; Wilson, Robin A; Manigrasso, Michaele B; Zhou, Boyan; Ruiz, Henry H; Mangar, Kaamashri; Higa, Ryoko; Brown, Emily; Li, Huilin; Garabedian, Michael J; Ramasamy, Ravichandran; Moore, Kathryn J; Fisher, Edward A; Theise, Neil D; Schmidt, Ann Marie
BACKGROUND & AIMS/UNASSIGNED:Metabolic syndrome-associated steatotic liver disease (MASLD) and metabolic syndrome-associated steatohepatitis (MASH) have global prevalence rates exceeding 25% and 3-6%, respectively. The introduction of high-fructose corn syrup to the diet in the 1970s has been linked to metabolic and hepatic disturbances. Despite these associations, the potential for sex-dependent responses resulting from fructose-containing diets on MASLD/MASH has not been addressed. METHODS/UNASSIGNED:standard chow for 16 weeks (n = 40 mice). At sacrifice, plasma and liver were retrieved, the latter for single-nucleus RNA sequencing. Publicly available data sets of human male and female MASH liver were probed. RESULTS/UNASSIGNED:0.0001). Single-nucleus RNA sequencing revealed distinct sex-specific transcriptional profiles in hepatocytes and stellate cells responding to the FPC-NASH diet compared to the standard chow. In female mice, compared to males, pathways associated with lipid and metabolic processes in hepatocytes and cell-cell communication and adhesion in stellate cells were enriched. Metabolic flux analyses demonstrated reduced bile acid metabolism in female mice and human hepatocytes in FPC-NASH and MASH conditions, respectively, compared to their male counterparts. CONCLUSIONS/UNASSIGNED:Molecular profiling of hepatocytes and stellate cells in FPC-NASH diet-fed mice revealed significant sex differences mirrored in human MASH. The identification of intrinsic, within-sex, diet-dependent disparities underscores the critical need to include both male and female individuals in MAFLD/MASH studies and clinical trials. IMPACT AND IMPLICATIONS/UNASSIGNED:male patients with MASH. These results highlight potential mechanistic explanations and therapeutic targets for addressing sex differences and underscore the need to study both sexes in animal models and human MASH.
PMCID:11795143
PMID: 39911943
ISSN: 2589-5559
CID: 5784202

Assessment of cardiac and skeletal muscle metabolites using 1H-MRS and chemical-shift encoded magnetic resonance imaging: Impact of diabetes, RAGE, and DIAPH1

Menon, Rajiv G; Yepuri, Gautham; Martel, Dimitri; Quadri, Nosirudeen; Hasan, Syed Nurul; Manigrasso, Michael B; Shekhtman, Alexander; Schmidt, Ann Marie; Ramasamy, Ravichandran; Regatte, Ravinder R
Diabetes affects metabolism and metabolite concentrations in multiple organs. Previous preclinical studies have shown that receptor for advanced glycation end products (RAGE, gene symbol Ager) and its cytoplasmic domain binding partner, Diaphanous-1 (DIAPH1), are key mediators of diabetic micro- and macro-vascular complications. In this study, we used 1H-Magnetic Resonance Spectroscopy (MRS) and chemical shift encoded (CSE) Magnetic Resonance Imaging (MRI) to investigate the metabolite and water-fat fraction in the heart and hind limb muscle in a murine model of type 1 diabetes (T1D) and to determine if the metabolite changes in the heart and hind limb are influenced by (a) deletion of Ager or Diaph1 and (b) pharmacological blockade of RAGE-DIAPH1 interaction in mice. Nine cohorts of male mice, with six mice per cohort, were used: wild type non-diabetic control mice (WT-NDM), WT-diabetic (WT-DM) mice, Ager knockout non-diabetic (RKO-NDM) and diabetic mice (RKO-DM), Diaph1 knockout non-diabetic (DKO-NDM), and diabetic mice (DKO-DM), WT-NDM mice treated with vehicle, WT-DM mice treated with vehicle, and WT-DM mice treated with RAGE229 (antagonist of RAGE-DIAPH1 interaction). A Point Resolved Spectroscopy (PRESS) sequence for 1H-MRS, and multi-echo gradient recalled echo (GRE) for CSE were employed. Triglycerides, and free fatty acids in the heart and hind limb obtained from MRS and MRI were compared to those measured using biochemical assays. Two-sided t-test, non-parametric Kruskal-Wallis Test, and one-way ANOVA were employed for statistical analysis. We report that the results were well-correlated with significant differences using MRI and biochemical assays between WT-NDM and WT-DM, as well as within the non-diabetic groups, and within the diabetic groups. Deletion of Ager or Diaph1, or treatment with RAGE229 attenuated diabetes-associated increases in triglycerides in the heart and hind limb in mice. These results suggest that the employment of 1H-MRS/MRI is a feasible non-invasive modality to monitor metabolic dysfunction in T1D and the metabolic consequences of interventions that block RAGE and DIAPH1.
PMID: 39468867
ISSN: 1099-1492
CID: 5746832

RAGE/DIAPH1 Axis and Cardiometabolic Disease: From Nascent Discoveries to Therapeutic Potential

Ramasamy, Ravichandran; Shekhtman, Alexander; Schmidt, Ann Marie
PMCID:11210684
PMID: 38924438
ISSN: 1524-4636
CID: 5697982

RAGE/DIAPH1 and atherosclerosis through an evolving lens: Viewing the cell from the "Inside - Out"

Ramasamy, Ravichandran; Shekhtman, Alexander; Schmidt, Ann Marie
BACKGROUND AND AIMS:In hyperglycemia, inflammation, oxidative stress and aging, Damage Associated Molecular Patterns (DAMPs) accumulate in conditions such as atherosclerosis. Binding of DAMPs to receptors such as the receptor for advanced glycation end products (RAGE) activates signal transduction cascades that contribute to cellular stress. The cytoplasmic domain (tail) of RAGE (ctRAGE) binds to the formin Diaphanous1 (DIAPH1), which is important for RAGE signaling. This Review will detail the evidence linking the RAGE/DIAPH1 signaling pathway to atherosclerosis and envisages future therapeutic opportunities from the "inside-out" point of view in affected cells. METHODS:PubMed was searched using a variety of search terms, including "receptor for advanced glycation end products" along with various combinations including "and atherosclerosis," "soluble RAGE and atherosclerosis," "statins and RAGE," "PPAR and RAGE" and "SGLT2 inhibitor and RAGE." RESULTS:. Associations between RAGE pathway and human atherosclerosis have been identified based on relationships between plasma/serum concentrations of RAGE ligands, soluble RAGEs and atherosclerosis. CONCLUSIONS:Efforts to target RAGE/DIAPH1 signaling through a small molecule antagonist therapeutic strategy hold promise to quell accelerated atherosclerosis in diabetes and in other forms of cardiovascular disease.
PMCID:11309734
PMID: 39131441
ISSN: 1879-1484
CID: 5706742

The RAGE/DIAPH1 axis: mediator of obesity and proposed biomarker of human cardiometabolic disease

Arivazhagan, Lakshmi; Popp, Collin J; Ruiz, Henry H; Wilson, Robin A; Manigrasso, Michaele B; Shekhtman, Alexander; Ramasamy, Ravichandran; Sevick, Mary Ann; Schmidt, Ann Marie
Overweight and obesity are leading causes of cardiometabolic dysfunction. Despite extensive investigation, the mechanisms mediating the increase in these conditions are yet to be fully understood. Beyond endogenous formation of advanced glycation end products (AGEs) in overweight and obesity, exogenous sources of AGEs accrue through the heating, production and consumption of highly-processed foods. Evidence from cellular and mouse model systems indicates that the interaction of AGEs with their central cell surface receptor for AGE (RAGE) in adipocytes suppresses energy expenditure and that AGE/RAGE contributes to increased adipose inflammation and processes linked to insulin resistance. In human subjects, the circulating soluble forms of RAGE, which are mutable, may serve as biomarkers of obesity and weight loss. Antagonists of RAGE signaling, through blockade of the interaction of the RAGE cytoplasmic domain with the formin, Diaphanous-1 (DIAPH1), target aberrant RAGE activities in metabolic tissues. This review focuses on the potential roles for AGEs and other RAGE ligands and RAGE/DIAPH1 in the pathogenesis of overweight and obesity and their metabolic consequences.
PMID: 36448548
ISSN: 1755-3245
CID: 5383622

The aldose reductase inhibitors AT-001, AT-003 and AT-007 attenuate human keratinocyte senescence

Yepuri, Gautham; Kancharla, Kushie; Perfetti, Riccardo; Shendelman, Shoshana; Wasmuth, Andrew; Ramasamy, Ravichandran
Human skin plays an important role protecting the body from both extrinsic and intrinsic factors. Skin aging at cellular level, which is a consequence of accumulation of irreparable senescent keratinocytes is associated with chronological aging. However, cell senescence may occur independent of chronological aging and it may be accelerated by various pathological conditions. Recent studies have shown that oxidative stress driven keratinocyte senescence is linked to the rate limiting polyol pathway enzyme aldose reductase (AR). Here we investigated the role of three novel synthetic AR inhibitors (ARIs) AT-001, AT-003 and AT-007 in attenuating induced skin cell senescence, in primary normal human keratinocytes (NHK cells), using three different senescence inducing agents: high glucose (HG), hydrogen peroxide (H2O2) and mitomycin-c (MMC). To understand the efficacy of ARIs in reducing senescence, we have assessed markers of senescence, including SA-β-galactosidase activity, γ-H2AX foci, gene expression of CDKN1A, TP53 and SERPINE1, reactive oxygen species generation and senescence associated secretory phenotypes (SASP). Strikingly, all three ARIs significantly inhibited the assessed senescent markers, after senescence induction. Our data confirms the potential role of ARIs in reducing NHK cell senescence and paves the way for preclinical and clinical testing of these ARIs in attenuating cell aging and aging associated diseases.
PMCID:11685203
PMID: 39741583
ISSN: 2673-6217
CID: 5805522

Disruption of the productive encounter complex results in dysregulation of DIAPH1 activity

Theophall, Gregory G; Ramirez, Lisa M S; Premo, Aaron; Reverdatto, Sergey; Manigrasso, Michaele B; Yepuri, Gautham; Burz, David S; Ramasamy, Ravichandran; Schmidt, Ann Marie; Shekhtman, Alexander
The diaphanous-related formin, Diaphanous 1 (DIAPH1), is required for the assembly of Filamentous (F)-actin structures. DIAPH1 is an intracellular effector of the receptor for advanced glycation end products (RAGE) and contributes to RAGE signaling and effects such as increased cell migration upon RAGE stimulation. Mutations in DIAPH1, including those in the basic "RRKR" motif of its autoregulatory domain, diaphanous autoinhibitory domain (DAD), are implicated in hearing loss, macrothrombocytopenia, and cardiovascular diseases. The solution structure of the complex between the N-terminal inhibitory domain, DID, and the C-terminal DAD, resolved by NMR spectroscopy shows only transient interactions between DID and the basic motif of DAD, resembling those found in encounter complexes. Cross-linking studies placed the RRKR motif into the negatively charged cavity of DID. Neutralizing the cavity resulted in a 5-fold decrease in the binding affinity and 4-fold decrease in the association rate constant of DAD for DID, indicating that the RRKR interactions with DID form a productive encounter complex. A DIAPH1 mutant containing a neutralized RRKR binding cavity shows excessive colocalization with actin and is unresponsive to RAGE stimulation. This is the first demonstration of a specific alteration of the surfaces responsible for productive encounter complexation with implications for human pathology.
PMCID:10656230
PMID: 37832872
ISSN: 1083-351x
CID: 5604342

DIAPH1-MFN2 interaction regulates mitochondria-SR/ER contact and modulates ischemic/hypoxic stress

Yepuri, Gautham; Ramirez, Lisa M; Theophall, Gregory G; Reverdatto, Sergei V; Quadri, Nosirudeen; Hasan, Syed Nurul; Bu, Lei; Thiagarajan, Devi; Wilson, Robin; Díez, Raquel López; Gugger, Paul F; Mangar, Kaamashri; Narula, Navneet; Katz, Stuart D; Zhou, Boyan; Li, Huilin; Stotland, Aleksandr B; Gottlieb, Roberta A; Schmidt, Ann Marie; Shekhtman, Alexander; Ramasamy, Ravichandran
Inter-organelle contact and communication between mitochondria and sarco/endoplasmic reticulum (SR/ER) maintain cellular homeostasis and are profoundly disturbed during tissue ischemia. We tested the hypothesis that the formin Diaphanous-1 (DIAPH1), which regulates actin dynamics, signal transduction and metabolic functions, contributes to these processes. We demonstrate that DIAPH1 interacts directly with Mitofusin-2 (MFN2) to shorten mitochondria-SR/ER distance, thereby enhancing mitochondria-ER contact in cells including cardiomyocytes, endothelial cells and macrophages. Solution structure studies affirm the interaction between the Diaphanous Inhibitory Domain and the cytosolic GTPase domain of MFN2. In male rodent and human cardiomyocytes, DIAPH1-MFN2 interaction regulates mitochondrial turnover, mitophagy, and oxidative stress. Introduction of synthetic linker construct, which shorten the mitochondria-SR/ER distance, mitigated the molecular and functional benefits of DIAPH1 silencing in ischemia. This work establishes fundamental roles for DIAPH1-MFN2 interaction in the regulation of mitochondria-SR/ER contact networks. We propose that targeting pathways that regulate DIAPH1-MFN2 interactions may facilitate recovery from tissue ischemia.
PMCID:10616211
PMID: 37903764
ISSN: 2041-1723
CID: 5610492