Profiling phagosome proteins identifies PD-L1 as a fungal-binding receptor.

Phagocytosis is the process by which myeloid phagocytes bind to and internalize potentially dangerous microorganisms1. During phagocytosis, innate immune receptors and associated signalling proteins are localized to the maturing phagosome compartment, forming an immune information processing hub brimming with microorganism-sensing features2-8. Here we developed proximity labelling of phagosomal contents (PhagoPL) to identify proteins localizing to phagosomes containing model yeast and bacteria. By comparing the protein composition of phagosomes containing evolutionarily and biochemically distinct microorganisms, we unexpectedly identified programmed death-ligand 1 (PD-L1) as a protein that specifically enriches in phagosomes containing yeast. We found that PD-L1 directly binds to yeast upon processing in phagosomes. By surface display library screening, we identified the ribosomal protein Rpl20b as a fungal protein ligand for PD-L1. Using an auxin-inducible depletion system, we found that detection of Rpl20b by macrophages cross-regulates production of distinct cytokines including interleukin-10 (IL-10) induced by the activation of other innate immune receptors. Thus, this study establishes PhagoPL as a useful approach to quantifying the collection of proteins enriched in phagosomes during host-microorganism interactions, exemplified by identifying PD-L1 as a receptor that binds to fungi.

ONECUT2 acts as a lineage plasticity driver in adenocarcinoma as well as neuroendocrine variants of prostate cancer.

Androgen receptor- (AR-) indifference is a mechanism of resistance to hormonal therapy in prostate cancer (PC). Here we demonstrate that ONECUT2 (OC2) activates resistance through multiple drivers associated with adenocarcinoma, stem-like and neuroendocrine (NE) variants. Direct OC2 gene targets include the glucocorticoid receptor (GR; NR3C1) and the NE splicing factor SRRM4, which are key drivers of lineage plasticity. Thus, OC2, despite its previously described NEPC driver function, can indirectly activate a portion of the AR cistrome through epigenetic activation of GR. Mechanisms by which OC2 regulates gene expression include promoter binding, enhancement of genome-wide chromatin accessibility, and super-enhancer reprogramming. Pharmacologic inhibition of OC2 suppresses lineage plasticity reprogramming induced by the AR signaling inhibitor enzalutamide. These results demonstrate that OC2 activation promotes a range of drug resistance mechanisms associated with treatment-emergent lineage variation in PC and support enhanced efforts to therapeutically target OC2 as a means of suppressing treatment-resistant disease.

A novel gain-of-function phosphorylation site modulates PTPN22 inhibition of TCR signaling.

Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) is encoded by a major autoimmunity gene and is a known inhibitor of T cell receptor (TCR) signaling and drug target for cancer immunotherapy. However, little is known about PTPN22 posttranslational regulation. Here, we characterize a phosphorylation site at Ser325 situated C terminal to the catalytic domain of PTPN22 and its roles in altering protein function. In human T cells, Ser325 is phosphorylated by glycogen synthase kinase-3 (GSK3) following TCR stimulation, which promotes its TCR-inhibitory activity. Signaling through the major TCR-dependent pathway under PTPN22 control was enhanced by CRISPR/Cas9-mediated suppression of Ser325 phosphorylation and inhibited by mimicking it via glutamic acid substitution. Global phospho-mass spectrometry showed Ser325 phosphorylation state alters downstream transcriptional activity through enrichment of Swi3p, Rsc8p, and Moira domain binding proteins, and next-generation sequencing revealed it differentially regulates the expression of chemokines and T cell activation pathways. Moreover, in vitro kinetic data suggest the modulation of activity depends on a cellular context. Finally, we begin to address the structural and mechanistic basis for the influence of Ser325 phosphorylation on the protein's properties by deuterium exchange mass spectrometry and NMR spectroscopy. In conclusion, this study explores the function of a novel phosphorylation site of PTPN22 that is involved in complex regulation of TCR signaling and provides details that might inform the future development of allosteric modulators of PTPN22.

Sumoylation of methionine adenosyltransferase alpha 1 promotes mitochondrial dysfunction in alcohol-associated liver disease.

BACKGROUND AND AIMS: Methionine adenosyltransferase alpha1 (MATα1) is responsible for the biosynthesis of S-adenosylmethionine in normal liver. Alcohol consumption enhances MATα1 interaction with peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1), which blocks MATα1 mitochondrial targeting, resulting in lower mitochondrial MATα1 content and mitochondrial dysfunction in alcohol-associated liver disease (ALD) in part through upregulation of cytochrome P450 2E1. Conversely, alcohol intake enhances SUMOylation, which enhances cytochrome P450 2E1 expression. MATα1 has potential SUMOylation sites, but whether MATα1 is regulated by SUMOylation in ALD is unknown. Here, we investigated if MATα1 is regulated by SUMOylation and, if so, how it impacts mitochondrial function in ALD. APPROACH AND RESULTS: Proteomics profiling revealed hyper-SUMOylation of MATα1, and prediction software identified lysine 48 (K48) as the potential SUMOylation site in mice (K47 in humans). Experiments with primary hepatocytes, mouse, and human livers revealed that SUMOylation of MAT1α by SUMO2 depleted mitochondrial MATα1. Furthermore, mutation of MATα1 K48 prevented ethanol-induced mitochondrial membrane depolarization, MATα1 depletion, and triglyceride accumulation. Additionally, CRISPR/CRISPR associated protein 9 gene editing of MATα1 at K48 hindered ethanol-induced MATα1-PIN1 interaction, degradation, and phosphorylation of MATα1 in vitro. In vivo, CRISPR/CRISPR associated protein 9 MATα1 K48 gene-edited mice were protected from ethanol-induced fat accumulation, liver injury, MATα1-PIN1 interaction, mitochondrial MATα1 depletion, mitochondrial dysfunction, and low S-adenosylmethionine levels. CONCLUSIONS: Taken together, our findings demonstrate an essential role for SUMOylation of MATα1 K48 for interaction with PIN1 in ALD. Preventing MATα1 K48 SUMOylation may represent a potential treatment strategy for ALD.

Genetic coding variant in complement factor B (CFB) is associated with increased risk for perianal Crohn's disease and leads to impaired CFB cleavage and phagocytosis.

OBJECTIVE: Perianal Crohn's disease (pCD) occurs in up to 40% of patients with CD and is associated with poor quality of life, limited treatment responses and poorly understood aetiology. We performed a genetic association study comparing CD subjects with and without perianal disease and subsequently performed functional follow-up studies for a pCD associated SNP in Complement Factor B (CFB). DESIGN: Immunochip-based meta-analysis on 4056 pCD and 11 088 patients with CD from three independent cohorts was performed. Serological and clinical variables were analysed by regression analyses. Risk allele of rs4151651 was introduced into human CFB plasmid by site-directed mutagenesis. Binding of recombinant G252 or S252 CFB to C3b and its cleavage was determined in cell-free assays. Macrophage phagocytosis in presence of recombinant CFB or serum from CFB risk, or protective CD or healthy subjects was assessed by flow cytometry. RESULTS: Perianal complications were associated with colonic involvement, OmpC and ASCA serology, and serology quartile sum score. We identified a genetic association for pCD (rs4151651), a non-synonymous SNP (G252S) in CFB, in all three cohorts. Recombinant S252 CFB had reduced binding to C3b, its cleavage was impaired, and complement-driven phagocytosis and cytokine secretion were reduced compared with G252 CFB. Serine 252 generates a de novo glycosylation site in CFB. Serum from homozygous risk patients displayed significantly decreased macrophage phagocytosis compared with non-risk serum. CONCLUSION: pCD-associated rs4151651 in CFB is a loss-of-function mutation that impairs its cleavage, activation of alternative complement pathway, and pathogen phagocytosis thus implicating the alternative complement pathway and CFB in pCD aetiology.

Dual kinase inhibitor for EGFR mutants and ErbB2 limit breast cancer.

Mutations in the epidermal growth factor receptor (EGFR) have been found in more than 10% of non-small cell lung cancer (NSCLC) patients in North America. The vast majority of these differences are L858R point mutations in Exon 21. Currently, monoclonal antibodies directed against the extracellular domain of EGFR or small molecule/tyrosine kinase inhibitors (TKI) are the stalwarts of NSCLC therapy. Resistance, however, gradually develops because of the T790 mutation towards first and second generation TKIs. The third generation TKI AZD9291 (Osimertinib) has a high affinity for both activating and the acquired resistant mutation (T790 M) in EGFR, with a low affinity towards wild-type EGFR. Recent research, however, suggests that the EGFR (C797S) mutation in the tyrosine kinase domain is a likely cause of resistance to AZD9291. Another significant transformation mechanism associated with this resistance is erbB2 amplification. Our laboratory has developed a small kinase inhibitor, ER121 (MW: ∼500), that inhibits the erbB2/HER2 tyrosine kinases in addition to the EGFR C797S mutations. We have identified a TKI, ER121 targeting the mutant EGFR(T790 M). Using in vitro and in vivo models, examined the efficacy of ER121 on mutant EGFR cell lines. This has enabled us to establish that ER121 is well tolerated when administered orally and produces significant inhibitory activity against human cancers generated by mutant EGFR and amplified ErbB2.

Dual targeting of GSK3B and HDACs reduces tumor growth and improves survival in an ovarian cancer mouse model.

OBJECTIVE: To investigate the anti-tumor effect of a newly-developed dual inhibitor (APCS-540) of glycogen synthase kinase 3 beta (GSK3B) and histone deacetylases (HDACs) in ovarian cancer cells. METHODS: The effects of APCS-540 on cancer cell proliferation, migration, invasion and cancer stemness were investigated in vitro in human (KURAMOCHI, OVCA420, OVSAHO) and mouse (BR-Luc, ID8, MOSE-HRas-Myc) ovarian cancer cells. Cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) cell lines were used to evaluate APCS-540's effect on chemoresistance. The immunocompetent syngeneic mouse model BR-Luc was used to test the effect of APCS-540 on ovarian cancer progression and survival. RESULTS: APCS-540 showed significant anti-tumor effects in vitro in both human and mouse ovarian cancer cells. Importantly, APCS-540 demonstrated marked cytotoxicity against cisplatin-resistant cancer cells and reversed cisplatin-resistance when used in combination with platinum. APCS-540 significantly decreased cancer cell invasion. A significant 66% increase in survival was observed in mice treated with APCS-540 compared to control mice. CONCLUSION: Dual inhibition of GSK3B and HDACs via APCS-540 showed potent anti-tumor activity in vitro and in vivo, suggesting that APCS-540 may provide a novel treatment option for ovarian cancer, including the platinum-resistant disease.

An Inhibitor of GSK3B and HDACs Kills Pancreatic Cancer Cells and Slows Pancreatic Tumor Growth and Metastasis in Mice.

BACKGROUND & AIMS: Growth, progression, and drug resistance of pancreatic ductal adenocarcinomas (PDACs) have been associated with increased levels and activity of glycogen synthase kinase 3 beta (GSK3B) and histone deacetylases (HDACs). We designed and synthesized molecules that simultaneously inhibit the activities of both enzymes. We tested the effects of one of these molecules, Metavert, in pancreatic cancer cells and mice with pancreatic tumors. METHODS: We tested the ability of Metavert to bind GSK3B and HDACs using surface plasmon resonance. MIA PaCa-2, Bx-PC3, HPAF-II, and HPDE6 cell lines were incubated with different concentrations of Metavert, with or without paclitaxel or gemcitabine, or with other inhibitors of GSK3B and HDACs; cells were analyzed for apoptosis and migration and by immunoblotting, immunofluorescence, and real-time polymerase chain reaction. Krasþ/LSLG12D;Trp53þ/LSLR172H;Pdx-1-Cre (KPC) mice (2 months old) were given injections of Metavert (5 mg/kg, 3 times/week) or vehicle (control). B6.129J mice with tumors grown from UN-KPC961-Luc cells were given injections of Metavert or vehicle. Tumors and metastases were counted and pancreata were analyzed by immunohistochemistry. Glucose metabolism was measured using 13C-glucose tracer and mass spectroscopy and flow cytometry. Cytokine levels in blood samples were measured using multiplexing enzyme-linked immunosorbent assay. RESULTS: Metavert significantly reduced survival of PDAC cells but not nontransformed cells; the agent reduced markers of the epithelial-to-mesenchymal transition and stem cells in PDAC cell lines. Cells incubated with Metavert in combination with irradiation and paclitaxel or gemcitabine had reduced survival compared with cells incubated with either agent alone; Metavert increased killing of drug-resistant PDAC cells by paclitaxel and gemcitabine. PDAC cells incubated with Metavert acquired normalized glucose metabolism. Administration of Metavert (alone or in combination with gemcitibine) to KPC mice or mice with syngeneic tumors significantly increased their survival times, slowed tumor growth, prevented tumor metastasis, decreased tumor infiltration by tumor-associated macrophages, and decreased blood levels of cytokines. CONCLUSIONS: In studies of PDAC cells and 2 mouse models of PDAC, we found a dual inhibitor of GSK3B and HDACs (Metavert) to induce cancer cell apoptosis, reduce migration and expression of stem cell markers, and slow growth of tumors and metastases. Metavert had synergistic effects with gemcitabine.

The induction of RANKL molecule clustering could stimulate early osteoblast differentiation.

We recently found that the membrane-bound receptor activator of NF-κB ligand (RANKL) on osteoblasts works as a receptor to stimulate osteoblast differentiation, however, the reason why the RANKL-binding molecules stimulate osteoblast differentiation has not been well clarified. Since the induction of cell-surface receptor clustering is known to lead to cell activation, we hypothesized that the induction of membrane-RANKL clustering on osteoblasts might stimulate osteoblast differentiation. Immunoblotting showed that the amount of RANKL on the membrane was increased by the RANKL-binding peptide OP3-4, but not by osteoprotegerin (OPG), the other RANKL-binding molecule, in Gfp-Rankl-transfected ST2 cells. Observation under a high-speed atomic force microscope (HS-AFM) revealed that RANKL molecules have the ability to form clusters. The induction of membrane-RANKL-OPG-Fc complex clustering by the addition of IgM in Gfp-Rankl-transfected ST2 cells could enhance the expression of early markers of osteoblast differentiation to the same extent as OP3-4, while OPG-Fc alone could not. These results suggest that the clustering-formation of membrane-RANKL on osteoblasts could stimulate early osteoblast differentiation.

Baicalein Targets GTPase-Mediated Autophagy to Eliminate Liver Tumor-Initiating Stem Cell-Like Cells Resistant to mTORC1 Inhibition.

Drug resistance is a major problem in the treatment of liver cancer. Mammalian Target of Rapamycin 1 (mTORC1) inhibitors have been tested for the treatment of liver cancer based on hyperactive mTOR in this malignancy. However, their clinical trials showed poor outcome, most likely due to their ability to upregulate CD133 and promote chemoresistance. The CD133+ tumor-initiating stem cell-like cells (TICs) isolated from mouse and human liver tumors are chemoresistant, and identification of an approach to abrogate this resistance is desired. In search of a compound that rescinds resistance of TICs to mTORC1 inhibition and improves chemotherapy, we identified baicalein (BC), which selectively chemosensitizes TICs and the human hepatocellular carcinoma (HCC) cell line Huh7 cells but not mouse and human primary hepatocytes. Nanobead pull-down and mass-spectrometric analysis, biochemical binding assay, and three-dimensional computational modeling studies reveal BC's ability to competitively inhibit guanosine triphosphate binding of SAR1B guanosine triphosphatase, which is essential for autophagy. Indeed, BC suppresses autophagy induced by an mTORC1 inhibitor and synergizes cell death caused by mTORC1 inhibition in TIC and Huh7 spheroid formation and in the patient-derived xenograft model of HCC. The BC-induced chemosensitization is rescued by SAR1B expression and phenocopied by SAR1B knockdown in cancer cells treated with a mTORC1 inhibitor. Conclusion: These results identify SAR1B as a target in liver TICs and HCC cells resistant to mTORC1 inhibition.

Direct Antimicrobial Activity of IFN-ß.

Type I IFNs are a cytokine family essential for antiviral defense. More recently, type I IFNs were shown to be important during bacterial infections. In this article, we show that, in addition to known cytokine functions, IFN-ß is antimicrobial. Parts of the IFN-ß molecular surface (especially helix 4) are cationic and amphipathic, both classic characteristics of antimicrobial peptides, and we observed that IFN-ß can directly kill Staphylococcus aureus Further, a mutant S. aureus that is more sensitive to antimicrobial peptides was killed more efficiently by IFN-ß than was the wild-type S. aureus, and immunoblotting showed that IFN-ß interacts with the bacterial cell surface. To determine whether specific parts of IFN-ß are antimicrobial, we synthesized IFN-ß helix 4 and found that it is sufficient to permeate model prokaryotic membranes using synchrotron x-ray diffraction and that it is sufficient to kill S. aureus These results suggest that, in addition to its well-known signaling activity, IFN-ß may be directly antimicrobial and be part of a growing family of cytokines and chemokines, called kinocidins, that also have antimicrobial properties.

Stearoyl-CoA Desaturase Promotes Liver Fibrosis and Tumor Development in Mice via a Wnt Positive-Signaling Loop by Stabilization of Low-Density Lipoprotein-Receptor-Related Proteins 5 and 6.

BACKGROUND & AIMS: Stearoyl-CoA desaturase (SCD) synthesizes monounsaturated fatty acids (MUFAs) and has been associated with the development of metabolic syndrome, tumorigenesis, and stem cell characteristics. We investigated whether and how SCD promotes liver fibrosis and tumor development in mice. METHODS: Rodent primary hepatic stellate cells (HSCs), mouse liver tumor-initiating stem cell-like cells (TICs), and human hepatocellular carcinoma (HCC) cell lines were exposed to Wnt signaling inhibitors and changes in gene expression patterns were analyzed. We assessed the functions of SCD by pharmacologic and conditional genetic manipulation in mice with hepatotoxic or cholestatic induction of liver fibrosis, orthotopic transplants of TICs, or liver tumors induced by administration of diethyl nitrosamine. We performed bioinformatic analyses of SCD expression in HCC vs nontumor liver samples collected from patients, and correlated levels with HCC stage and patient mortality. We performed nano-bead pull-down assays, liquid chromatography-mass spectrometry, computational modeling, and ribonucleoprotein immunoprecipitation analyses to identify MUFA-interacting proteins. We examined the effects of SCD inhibition on Wnt signaling, including the expression and stability of low-density lipoprotein-receptor-related proteins 5 and 6 (LRP5 and LRP6), by immunoblot and quantitative polymerase chain reaction analyses. RESULTS: SCD was overexpressed in activated HSC and HCC cells from patients; levels of SCD messenger RNA (mRNA) correlated with HCC stage and patient survival time. In rodent HSCs and TICs, the Wnt effector ß-catenin increased sterol regulatory element binding protein 1-dependent transcription of Scd, and ß-catenin in return was stabilized by MUFAs generated by SCD. This loop required MUFA inhibition of binding of Ras-related nuclear protein 1 (Ran1) to transportin 1 and reduced nuclear import of elav-like protein 1 (HuR), increasing cytosolic levels of HuR and HuR-mediated stabilization of mRNAs encoding LRP5 and LRP6. Genetic disruption of Scd and pharmacologic inhibitors of SCD reduced HSC activation and TIC self-renewal and attenuated liver fibrosis and tumorigenesis in mice. Conditional disruption of Scd2 in activated HSCs prevented growth of tumors from TICs and reduced the formation of diethyl nitrosamine-induced liver tumors in mice. CONCLUSIONS: In rodent HSCs and TICs, we found SCD expression to be regulated by Wnt-ß-catenin signaling, and MUFAs produced by SCD provided a forward loop to amplify Wnt signaling via stabilization of Lrp5 and Lrp6 mRNAs, contributing to liver fibrosis and tumor growth. SCD expressed by HSCs promoted liver tumor development in mice. Components of the identified loop linking HSCs and TICs might be therapeutic targets for liver fibrosis and tumors.

Peptide drugs accelerate BMP-2-induced calvarial bone regeneration and stimulate osteoblast differentiation through mTORC1 signaling.

Both W9 and OP3-4 were known to bind the receptor activator of NF-κB ligand (RANKL), inhibiting osteoclastogenesis. Recently, both peptides were shown to stimulate osteoblast differentiation; however, the mechanism underlying the activity of these peptides remains to be clarified. A primary osteoblast culture showed that rapamycin, an mTORC1 inhibitor, which was recently demonstrated to be an important serine/threonine kinase for bone formation, inhibited the peptide-induced alkaline phosphatase activity. Furthermore, both peptides promoted the phosphorylation of Akt and S6K1, an upstream molecule of mTORC1 and the effector molecule of mTORC1, respectively. In the in vivo calvarial defect model, W9 and OP3-4 accelerated BMP-2-induced bone formation to a similar extent, which was confirmed by histomorphometric analyses using fluorescence images of undecalcified sections. Our data suggest that these RANKL-binding peptides could stimulate the mTORC1 activity, which might play a role in the acceleration of BMP-2-induced bone regeneration by the RANKL-binding peptides.

The intra-articular injection of RANKL-binding peptides inhibits cartilage degeneration in a murine model of osteoarthritis.

We recently found that the receptor activator of NF-κB ligand (RANKL)-binding peptide, OP3-4 stimulated the differentiation of both chondrocytes and osteoblasts. OP3-4 is also shown to inhibit cartilage degeneration. To clarify whether the peptide can inhibit cartilage degeneration without stimulating bone formation, we first performed a proliferation assay using C3H10T1/2 (the murine mesenchymal stem cell line), which is the common origin of both chondrocytes and osteoblasts. The RANKL-binding peptides, OP3-4 and W9, promoted cellular proliferation at 24 and 48 h, respectively. Next, we injected both peptides into the intra-articular space of the knee joints of mice with monosodium-iodoacetate (MIA)-induced osteoarthritis to clarify the effects of the peptides on cartilage tissue. Twenty-five nine-week-old male C57BL/6J mice received injections of vehicle, or the same molar amount of W9, OP3-4, or a control peptide (which could not stimulate osteoblast differentiation) on days 7, 14, and 21 after the injection of MIA. The mice were sacrificed on day 28. The histomorphometric analyses revealed that both peptides inhibited the degeneration of cartilage without enhancing bone formation activity. Our data suggest that the stimulation of mesenchymal cell proliferation by the RANKL-binding peptides might lead to the inhibition of cartilage degeneration.

HER2-positive breast cancer targeting and treatment by a peptide-conjugated mini nanodrug.

HER2+ breast cancer is one of the most aggressive forms of breast cancer. The new polymalic acid-based mini nanodrug copolymers are synthesized and specifically characterized to inhibit growth of HER2+ breast cancer. These mini nanodrugs are highly effective and in the clinic may substitute for trastuzumab (the marketed therapeutic antibody) and antibody-targeted nanobioconjugates. Novel mini nanodrugs are designed to have slender shape and small size. HER2+ cells were recognized by the polymer-attached trastuzumab-mimetic 12-mer peptide. Synthesis of the nascent cell-transmembrane HER2/neu receptors by HER2+ cells was inhibited by antisense oligonucleotides that prevented cancer cell proliferation and significantly reduced tumor size by more than 15 times vs. untreated control or PBS-treated group. We emphasize that the shape and size of mini nanodrugs can enhance penetration of multiple bio-barriers to facilitate highly effective treatment. Replacement of trastuzumab by the mimetic peptide favors reduced production costs and technical efforts, and a negligible immune response.

Mitochondrial protein BmPAPI modulates the length of mature piRNAs.

PIWI proteins and their associated PIWI-interacting RNAs (piRNAs) protect genome integrity by silencing transposons in animal germlines. The molecular mechanisms and components responsible for piRNA biogenesis remain elusive. PIWI proteins contain conserved symmetrical dimethylarginines (sDMAs) that are specifically targeted by TUDOR domain-containing proteins. Here we report that the sDMAs of PIWI proteins play crucial roles in PIWI localization and piRNA biogenesis in Bombyx mori-derived BmN4 cells, which harbor fully functional piRNA biogenesis machinery. Moreover, RNAi screenings for Bombyx genes encoding TUDOR domain-containing proteins identified BmPAPI, a Bombyx homolog of Drosophila PAPI, as a factor modulating the length of mature piRNAs. BmPAPI specifically recognized sDMAs and interacted with PIWI proteins at the surface of the mitochondrial outer membrane. BmPAPI depletion resulted in 3'-terminal extensions of mature piRNAs without affecting the piRNA quantity. These results reveal the BmPAPI-involved piRNA precursor processing mechanism on mitochondrial outer membrane scaffolds.

Human immunodeficiency virus type 1 Vpr polymorphisms associated with progressor and nonprogressor individuals alter Vpr-associated functions.

Following infection with Human immunodeficiency virus 1 (HIV-1) there is a remarkable variation in virus replication and disease progression. Both host and viral factors have been implicated in the observed differences in disease status. Here, we focus on understanding the contribution of HIV-1 viral protein R (Vpr) by evaluating the disease-associated Vpr polymorphism and its biological functions from HIV-1 positive rapid progressor (RP) and long-term nonprogressor (LTNP) subjects. Results presented here show distinct variation in phenotypes of Vpr alleles from LTNP and RP subjects. Most notably, the polymorphism of Vpr at R36W and L68M associated with RP shows higher levels of oligomerization, and increased virus replication, whereas R77Q exhibits poor replication kinetics. Interestingly, we did not observe correlation with cell cycle arrest function. Together these results indicate that polymorphisms in Vpr in part may contribute to altered virus replication kinetics leading to the observed differences in disease progression in LTNP and RP groups.

Structures of Cutibacterium acnes hyaluronate lyases suggest a correlation between active site opened/closed state and conformation of abutting loop.

The structures of hyaluronate lyases from two Cutibacterium acnes strains have been reported recently and show open catalytic clefts. We compared these open structures with more closed structures of homologous lyases and found that the conformation of a loop that abuts the catalytic cleft is seemingly correlated with the opening and closing of the cleft. We illustrate that the loop conformation seen in the open lyase appears incompatible with a closed catalytic cleft, and vice versa; however, mutations designed to disrupt the loop conformation did not significantly affect catalytic activity.

A novel micropeptide, Slitharin, exerts cardioprotective effects in myocardial infarction.

PURPOSE: Micropeptides are an emerging class of proteins that play critical roles in cell signaling. Here, we describe the discovery of a novel micropeptide, dubbed slitharin (Slt), in conditioned media from Cardiosphere-derived cells (CDCs), a therapeutic cardiac stromal cell type. EXPERIMENTAL DESIGN: We performed mass spectrometry of peptide-enriched fractions from the conditioned media of CDCs and a therapeutically inert cell type (human dermal fibrobasts). We then evaluated the therapeutic capacity of the candidate peptide using an in vitro model of cardiomyocyte injury and a rat model of myocardial infarction. RESULTS: We identified a novel 24-amino acid micropeptide (dubbed Slitharin [Slt]) with a non-canonical leucine start codon, arising from long intergenic non-coding (LINC) RNA 2099. Neonatal rat ventricular myocytes (NRVMs) exposed to Slt were protected from hypoxic injury in vitro compared to a vehicle or scrambled control. Transcriptomic analysis of cardiomyocytes exposed to Slt reveals cytoprotective capacity, putatively through regulation of stress-induced MAPK-ERK. Slt also exerted cardioprotective effects in rats with myocardial infarction as shown by reduced infarct size 48 h post-injury. Conclusions and clinical relavance: Thus, Slt is a non-coding RNA-derived micropeptide, identified in the extracellular space, with a potential cardioprotective function.