Delivering drugs to the specific kidney cells remains a significant challenge in treating renal disorders. This chapter introduces a novel renal tubule targeting carbohydrate (RENTAC) ligand to precisely deliver peptide nucleic acid (PNA) to the proximal convoluted tubules of the kidney. We have reported the synthesis of the RENTAC ligand and a solution-phase PNA conjugation and characterization method. The methodology for elucidating the cellular uptake mechanism in cell culture and comprehensive biodistribution studies and evaluating the PNA-RENTAC conjugate efficacy in kidney fibrosis models is detailed. The reported methods are thoroughly validated and robust. This approach of ligand-mediated precise kidney delivery of PNA opens a vast platform for treating kidney disorders using antisense and antigene technologies.

Physical activity is well-known to protect the heart against ischemia-reperfusion (I/R) injury, yet the underlying mechanisms, particularly those involving interorgan crosstalk, remain incompletely understood. This study investigated whether activation of the skeletal muscle (SkM) Nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant system confers cardioprotection by promoting antioxidant transfer via extracellular vesicles and non-vesicular extracellular nanoparticles (EVs/nvENPs). We utilized iMS-Keap1flox/flox mice, a transgenic model generated in our laboratory (Gao et al., 2020; PMID: 32893883), in which SkM-specific Keap1 knockout (KO) selectively activates Nrf2 and upregulates SkM antioxidant enzymes. Under isoflurane anesthesia, a Millar pressure transducer was inserted into the left ventricular cavity to continuously assess real-time cardiac function, quantified by the cardiac contractility index (CCI), throughout the I/R protocol (60-min ischemia/60-min reperfusion with 20-min baseline). Following functional assessment, hearts were collected for TTC infarct staining; soleus muscle, myocardium, and plasma EVs/nvENPs were analyzed by Western blot for antioxidant enzymes; and left ventricular myocardium was subjected to mass spectrometry-based proteomics and pathway enrichment analysis. We found that, while ischemia depressed cardiac function similarly in both WT and KO mice, the reperfusion response diverged markedly. WT mice exhibited further deterioration during reperfusion (CCI: baseline 156.98 ± 14.97 1/s; ischemia 86.43 ± 10.33 1/s; reperfusion 44.15 ± 9.13 1/s; p < 0.01 between the three phases, n = 6), consistent with additional reperfusion-induced injury. In contrast, KO mice demonstrated significant functional improvement during reperfusion (CCI: baseline 165.44 ± 18.65 1/s; ischemia 98.86 ± 13.62 1/s; reperfusion 121.44 ± 11.73 1/s; p < 0.01 between the three phases, n = 6), suggesting partial rescue of ischemic myocardium. TTC staining confirmed reduced infarct size in KO versus WT mice (24.05 ± 3.37% vs. 34.56 ± 2.59%, p < 0.001, n = 6/group). Western blot analysis showed markedly elevated antioxidant enzymes (NQO1 and GSTA2) in the soleus muscle, plasma EVs/nvENPs, and myocardium of KO mice, supporting a mechanism of systemic antioxidant transfer. On the other hand, the upregulated Nrf2 protein was detected only in soleus muscle of KO mice, excluding an off-target effect of SkM Nrf2 activation. Proteomics of KO mouse myocardium revealed enrichment of additional cardioprotective pathways, including TCA cycle II, integrin-linked kinase signaling, integrin signaling, and paxillin signaling. These findings demonstrate that selective activation of the SkM Nrf2-antioxidant system confers substantial protection against myocardial I/R injury, potentially through circulating EV/nvENP-mediated interorgan antioxidant delivery. Targeting skeletal muscle Nrf2-antioxidant pathways may represent a promising therapeutic strategy to enhance cardiac resilience to I/R injury. Supported by NIH R01HL160820. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Summary Sumoylation is a post-translational modification that can regulate different physiological functions. Increased sumoylation, specifically conjugation of SUMO2/3 (small ubiquitin like modifier 2/3), is detrimental to vascular health. However, the molecular mechanism mediating this effect is poorly understood. Here, we demonstrate that SUMO2 modifies p66Shc, which impairs endothelial function. Using multiple approaches, we show that p66Shc is a direct target of SUMO2. Mass spectrometry identified that SUMO2 modified lysine-81 in the unique collagen homology-2 domain of p66Shc. SUMO2ylation of p66Shc increased phosphorylation at serine-36, causing it to translocate to the mitochondria. Notably, sumoylation-deficient p66Shc (p66ShcK81R) was resistant to SUMO2-induced p66ShcS36 phosphorylation and mitochondrial translocation. Ingenuity pathway analysis showed that majority of effects of p66Shc SUMO2ylation were mediated via p66ShcK81. Finally, p66ShcK81R knockin mice were resistant to SUMO2-induced endothelial dysfunction. Collectively, our work uncovers a posttranslational modification of redox protein p66Shc and identifies SUMO2-p66Shc signaling as a regulator of vascular endothelial function.

RdRp is a critical component of an RNA virus life cycle. Among coronaviruses, NSP12, along with one copy of NSP7 and two copies of NSP8, forms the RdRp holoenzyme and exhibits polymerase activity. While coronavirus RNA replication is sufficiently understood, the interplay among these NSPs and its influence on RNA binding and nascent strand synthesis remains poorly understood. Here, we reconstituted a functional RdRp holoenzyme using recombinant SARS-CoV-2 NSP12, NSP7, and NSP8 in vitro. Molecular interactions among NSPs and their effect on the polymerase activity were investigated, wherein NSP12 alone exhibited notable activity, which was further enhanced by the presence of both NSP7 and NSP8. The presence of only one cofactor, either NSP7 or NSP8, completely inhibited NSP12 activity and led to RNA template detachment. Computational analyses of different NSP12 complexes suggested that binding of NSP7 or NSP8 alone to NSP12 constricts the RNA entry channel, which was higher in the presence of NSP8, making it inappropriate for RNA entry/binding. We conclude that NSP7 and NSP8 together synergize to enhance the NSP12 activity, but antagonize when alone. These findings have implications for novel drug development, and compounds inhibiting NSP7 or NSP8 interactions with NSP12 can be lethal to coronavirus replication.

V(D)J recombination is constrained by timely degradation of the RAG1 and RAG2 proteins through distinct mechanisms. Previously, we showed that full-length RAG1 stability is regulated by viral protein R binding protein (VprBP) through its association with an amino-terminal region in RAG1, but the mechanism remains unclear. As an unbiased approach to uncover potential cofactors involved in the process, we compared protein interactomes between RAG1/RAG2 complexes formed when the amino-terminal third of RAG1 was present or absent. These experiments identified RACK1 as preferentially associating with full-length RAG1. Because RACK1 is implicated in mediating protein degradation in other contexts, we evaluated how loss of RACK1 in B cells affects B cell development and V(D)J recombination. We find that conditional disruption of Rack1 expression in the B lineage in mice blocks B cell development at the pro-B cell stage and impairs V(D)J recombination after Igh DH-JH rearrangement. In this background, enforced Bcl2 expression does not significantly rescue B cell development but does enable the V(D)J recombination defect to be bypassed. However, the phenotype of these mice does not show the excessive Igk rearrangement, skewing toward Igλ+ B cells, or increased RAG1 protein levels observed when VprBP expression is similarly disrupted in B cells, arguing against RACK1 serving as a cofactor in RAG1 degradation. Further studies provide evidence that loss of RACK1 in primary B cells dysregulates cell cycle progression, apoptosis, proliferation, and signaling through MAPK and NF-κB pathways.

In late December 2019, SARS-CoV-2 emerged in Wuhan, China. Since then, several variants have been identified. The delta variant, a variant of concern, originated in Lucknow, India. Since then, there has been an urgent need to develop effective therapeutics and vaccine candidates against SARS-CoV-2. Virus-Like Particles (VLPs) are promising vaccine candidates. The advantage of VLP-based vaccines is that they resemble viral structures. In this study, we developed SARS-CoV-2 Virus-Like Particles. The docking and MD simulations analysis confirmed the presence of strong interactions between M and E proteins. The purified VLPs were confirmed by TEM and FESEM, with a size range of 100-120 nm. Immunization of BALB/c mice with purified VLPs elicited a strong immune response, as measured by ELISA. The immunized mice serum showed high titers of IgG, IgM, and IFN-γ. qRT-PCR cytokine analysis showed a Th1/Th2 response. The virus-neutralization assay confirmed the presence of neutralizing antibodies in the sera of immunized mice. These results show that VLP-based vaccines can be effective against SARS-CoV-2 and constitute a scalable, safe, and effective vaccine platform.

Background: Aging elevates reactive oxygen species (ROS) and weakens antioxidant defenses, contributing to cardiac dysfunction. The objective of this study was to determine whether sustained activation of skeletal muscle (SkM) Nrf2 preserves cardiac function during aging and to explore the underlying mechanisms, focusing on myocardial antioxidant pathways. Methods: Tamoxifen-induced SkM-specific Keap1 knockout male mice (iMS-Keap1flox/flox; SkM-Nrf2 overexpression) were divided into young wild-type (Y-WT), aged wild-type (A-WT), and aged knockout (A-KO) groups. Cardiac performance was evaluated by echocardiography and invasive hemodynamics. Myocardial proteomics identified differentially expressed proteins (DEPs) and enriched biological pathways. Results: Compared with Y-WT, A-WT mice showed impaired left ventricular function, including reduced ejection fraction, prolonged isovolumic relaxation time, blunted inotropic response to dobutamine, and elevated Tau index. These age-related deficits were partially reversed in A-KO mice. Proteomic analysis revealed 561 DEPs between A-WT and Y-WT, and 741 DEPs between A-KO and A-WT, enriched in calcium signaling, Nrf2-mediated oxidative stress response, oxidative phosphorylation, ROS detoxification, and cardiac-specific processes, such as hypertrophy, conduction, and dilated cardiomyopathy. Conclusions: Lifelong SkM-Nrf2 activation strengthens myocardial antioxidant capacity and alleviates age-related cardiac dysfunction. These data support an antioxidant crosstalk between skeletal muscle and the heart, highlighting a potential therapeutic target for aging-associated heart failure.

BACKGROUND:The earliest manifestation of alcohol-associated liver disease (ALD) is steatosis characterized by deposition of fat in specialized organelles called lipid droplets (LDs). While alcohol administration causes a rise in LD numbers in the hepatocytes, little is known regarding their characteristics that allow their accumulation and size to increase. The aim of the present study is to gain insights into underlying pathophysiological mechanisms by investigating the ethanol-induced changes in hepatic LD proteome as a function of LD size. METHODS:Adult male Wistar rats (180-200 g BW) were fed with ethanol liquid diet for 6 weeks. At sacrifice, large-, medium-, and small-sized hepatic LD subpopulations (LD1, LD2, and LD3, respectively) were isolated and subjected to morphological and proteomic analyses. RESULTS:Morphological analysis of LD1-LD3 fractions of ethanol-fed rats clearly demonstrated that LD1 contained larger LDs compared with LD2 and LD3 fractions. Our preliminary results from principal component analysis showed that the proteome of different-sized hepatic LD fractions was distinctly different. Proteomic data analysis identified over 2000 proteins in each LD fraction with significant alterations in protein abundance among the three LD fractions. Among the altered proteins, several were related to fat metabolism, including synthesis, incorporation of fatty acid, and lipolysis. Ingenuity pathway analysis revealed increased fatty acid synthesis, fatty acid incorporation, LD fusion, and reduced lipolysis in LD1 compared to LD3. Overall, the proteomic findings indicate that the increased level of protein that facilitates fusion of LDs combined with an increased association of negative regulators of lipolysis dictates the generation of large-sized LDs during the development of alcohol-associated hepatic steatosis. CONCLUSION:Several significantly altered proteins were identified in different-sized LDs isolated from livers of ethanol-fed rats. Ethanol-induced increases in specific proteins that hinder LD lipid metabolism led to the accumulation and persistence of large-sized LDs in the liver.

Hepatocellular carcinoma (HCC), with its increasing prevalence globally, is emerging as a major health challenge. Hepatocellular carcinoma cells exhibit both significant homogeneity and heterogeneity, governed by complex epigenomic regulations. Recently, numerous single-cell unimodal techniques have been used to study HCC at various levelswhich have already revealed a complex interplay at genomic, transcriptomic, spatial and epigenomic levels. However, the use of single-cell multimodal techniques combining different unimodal layers in HCC remains quite limited, necessitating further studies focusing on these methods to uncover novel markers, and mechanisms at epigenetic levels. In this commentary, we highlight how integrating multimodal approaches with epigenetic modifications can provide new insights into HCC and foster future therapeutic advancements.

The molecular mechanisms underlying neurite formation include multiple crosstalk between pathways such as membrane trafficking, intracellular signaling, and actin cytoskeletal rearrangement. To study the proteins involved in such complex pathways, we present a detailed workflow of the sample preparation for mass spectrometry-based proteomics and data analysis. We have also included steps to perform label-free quantification of proteins that will help researchers quantify changes in the expression levels of key regulators of neuronal morphogenesis on a global scale.

The ability of tumour cells to thrive in harsh microenvironments depends on the utilization of nutrients available in the milieu. Here we show that pancreatic cancer-associated fibroblasts (CAFs) regulate tumour cell metabolism through the secretion of acetate, which can be blocked by silencing ATP citrate lyase (ACLY) in CAFs. We further show that acetyl-CoA synthetase short-chain family member 2 (ACSS2) channels the exogenous acetate to regulate the dynamic cancer epigenome and transcriptome, thereby facilitating cancer cell survival in an acidic microenvironment. Comparative H3K27ac ChIP–seq and RNA–seq analyses revealed alterations in polyamine homeostasis through regulation of SAT1 gene expression and enrichment of the SP1-responsive signature. We identified acetate/ACSS2-mediated acetylation of SP1 at the lysine 19 residue that increased SP1 protein stability and transcriptional activity. Genetic or pharmacologic inhibition of the ACSS2–SP1–SAT1 axis diminished the tumour burden in mouse models. These results reveal that the metabolic flexibility imparted by the stroma-derived acetate enabled cancer cell survival under acidosis via the ACSS2–SP1–SAT1 axis. Murthy et al. demonstrate that cancer-associated fibroblast-derived acetate regulates polyamine homeostasis via an ACSS2–SP1–SAT1 axis in pancreatic cancer cells, thus enabling cell survival and tumour development under acidosis.

Objective: Circulating exosome-enriched extracellular vesicles (EVs) have drawn considerable importance in obesity-related insulin-resistance (IR). We sought to compare the proteomics profile of serum exosomes from normal individuals and those with obesity and IR. Methods: We isolated serum exosomes from male subjects with obesity and insulin resistance (Ob-IR, HOMA-IR > 2.0) and lean/overweight insulin-sensitive (Normal (N), HOMA-IR < 2.0) individuals. The differential protein expression between the two groups was detected by a label-free quantitative mass spectrometry analysis followed by GO annotation and ingenuity pathway analysis (IPA). Results: We identified 23 upregulated and 46 downregulated proteins between Ob-IR and N groups. Some of these proteins are involved in altering insulin signaling (VPS13C, TBC1D32, TTR, and ADIPOQ), inflammation (NFκB and CRP), and B-cell proliferation/activation (IGLV4-69, IGKV1D-13, and IGHV4-28). GO analysis revealed that the differentially expressed proteins (DEPs) are mainly involved in regulating immune cell activation and are located in extracellular space. IPA analysis showed that top molecules mediating IR, inflammation and B-cell activation were upregulated in Ob-IR subjects compared to N subjects. Conclusions: Serum exosomal proteins can be used as biomarkers to identify the future risk of diabetes and a therapeutic target to prevent or slow down the progression of diabetes in high-risk individuals.

Lamins form a proteinaceous meshwork as a major structural component of the nucleus. Lamins, along with their interactors, act as determinants for chromatin organization throughout the nucleus. The major dominant missense mutations responsible for autosomal dominant forms of muscular dystrophies reside in the Ig fold domain of lamin A. However, how lamin A contributes to the distribution of heterochromatin and balances euchromatin, and how it relocates epigenetic marks to shape chromatin states, remains poorly defined, making it difficult to draw conclusions about the prognosis of lamin A-mediated muscular dystrophies. In the first part of this report, we identified the in vitro organization of full-length lamin A proteins due to two well-documented Ig LMNA mutations, R453W and W514R. We further demonstrated that both lamin A/C mutant cells predominantly expressed nucleoplasmic aggregates. Labeling specific markers of epigenetics allowed correlation of lamin A mutations with epigenetic mechanisms. In addition to manipulating epigenetic mechanisms, our proteomic studies traced diverse expressions of transcription regulators, RNA synthesis and processing proteins, protein translation components, and posttranslational modifications. These data suggest severe perturbations in targeting other proteins to the nucleus.

Fatty liver is the earliest response of the liver to excessive alcohol consumption. Previously we identified that chronic alcohol administration increases levels of stomach-derived hormone, ghrelin, which by reducing circulating insulin levels, ultimately contributes to the development of alcohol-associated liver disease (ALD). In addition, ghrelin directly promotes fat accumulation in hepatocytes by enhancing de novo lipogenesis. Other than promoting ALD, ghrelin is known to increase alcohol craving and intake. In this study, we used a ghrelin receptor (GHSR) knockout (KO) rat model to characterize the specific contribution of ghrelin in the development of ALD with emphasis on energy homeostasis. Male Wistar wild type (WT) and GHSR-KO rats were pair-fed the Lieber-DeCarli control or ethanol diet for 6 weeks. At the end of the feeding period, glucose tolerance test was conducted, and tissue samples were collected. We observed reduced alcohol intake by GHSR-KOs compared to a previous study where WT rats were fed ethanol diet ad libitum. Further, when the WTs were pair-fed to GHSR-KOs, the KO rats exhibited resistance to develop ALD through improving insulin secretion/sensitivity to reduce adipose lipolysis and hepatic fatty acid uptake/synthesis and increase fatty acid oxidation. Furthermore, proteomic data revealed that ethanol-fed KO exhibit less alcohol-induced mitochondrial dysfunction and oxidative stress than WT rats. Proteomic data also confirmed that the ethanol-fed KOs are insulin sensitive and are resistant to hepatic steatosis development compared to WT rats. Together, these data confirm that inhibiting ghrelin action prevent alcohol-induced liver and adipose dysfunction independent of reducing alcohol intake.

Liver disease is one of the leading comorbidities in HIV infection. The risk of liver fibrosis development is potentiated by alcohol abuse. In our previous studies, we reported that hepatocytes exposed to HIV and acetaldehyde undergo significant apoptosis, and the engulfment of apoptotic bodies (ABs) by hepatic stellate cells (HSC) potentiates their pro-fibrotic activation. However, in addition to hepatocytes, under the same conditions, ABs can be generated from liver-infiltrating immune cells. The goal of this study is to explore whether lymphocyte-derived ABs trigger HSC profibrotic activation as strongly as hepatocyte-derived ABs. ABs were generated from Huh7.5-CYP2E1 (RLW) cells and Jurkat cells treated with HIV+acetaldehyde and co-culture with HSC to induce their pro-fibrotic activation. ABs cargo was analyzed by proteomics. ABs generated from RLW, but not from Jurkat cells activated fibrogenic genes in HSC. This was driven by the expression of hepatocyte-specific proteins in ABs cargo. One of these proteins is Hepatocyte-Derived Growth Factor, for which suppression attenuates pro-fibrotic activation of HSC. In mice humanized with only immune cells but not human hepatocytes, infected with HIV and fed ethanol, liver fibrosis was not observed. We conclude that HIV+ABs of hepatocyte origin promote HSC activation, which potentially may lead to liver fibrosis progression.

SUMOylation is a highly dynamic post-translational modification which regulates protein function and/or stability. It involves conjugation of SUMOs ( S mall U biquitin-Like Mo difier s ) to the lysine residue/s of target proteins mediated via a highly coordinated enzymatic mechanism. Studies have shown that promoting SUMOylation (SUMO2/3) causes vascular endothelial dysfunction and accelerates atherosclerosis. We reported that SUMO2 overexpression in endothelial cells promotes oxidative stress and impairs endothelial function. However, the mechanism is not well understood. Adaptor protein p66Shc is a master regulator of oxidative stress and endothelial function. Genetic deletion of p66Shc protects mice against endothelial dysfunction due to metabolic dysregulation. Prior studies have shown that lysine modification of p66Shc regulates its oxidative function. As SUMOylation primarily occurs on lysine residue, we examined if p66Shc is a target of SUMO2. In this study, we show that p66Shc is a direct target of SUMO2. Using endothelial cells and HEK-293 cells, we show that overexpression of SUMO2 leads to p66Shc SUMO2ylation which is further increased in presence of E2-ligase Ubc9 and reduced by deSUMOylating enzyme SENP1. SUMO2ylation of p66Shc increases oxidative activation (serine-36 phosphorylation) of p66Shc which is essential for reactive oxygen production by p66Shc. Using mass spectroscopic study, we identified that lysine-81 is the only lysine present in CH2 domain which is getting SUMO2ylated. Rendering p66ShcK81 non-sumoylatable (p66ShcK81R) prevented the SUMO2ylation of p66Shc. In endothelial cells, overexpression of p66ShcK81R prevented the SUMO2-induced increase in serine-36 phosphorylation and mitochondrial translocation of p66Shc, which are essential for oxidative function of p66Shc. Collectively, we present a novel molecular mechanism via which SUMO2 regulates the oxidative function of p66Shc and identify a unique post-translational regulation of p66Shc in endothelial cells.