Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors.     

Regulation of ATP-sensitive K(+) channels by protein kinase C in murine colonic myocytes

We investigated the regulation ofATP-sensitive K⁺ (K_ATP) currents in murinecolonic myocytes with patch-clamp techniques. Pinacidil(10⁵ M) activated inward currents in the presence of highexternal K⁺ (90 mM) at a holding potential of 80 mV indialyzed cells. Glibenclamide (10⁵ M) suppressedpinacidil-activated current. Phorbol 12,13-dibutyrate (PDBu; 2 × 10⁷ M) inhibited pinacidil-activated current.4--Phorbol ester (5 × 10⁷ M), an inactive formof PDBu, had no effect on pinacidil-activated current. In cell-attachedpatches, the open probability of K_ATP channels wasincreased by pinacidil, and PDBu suppressed openings ofK_ATP channels. When cells were pretreated withchelerythrine (10⁶ M) or calphostin C (10⁷M), inhibition of the pinacidil-activated whole cell currents by PDBuwas significantly reduced. In cells studied with the perforated patchtechnique, PDBu also inhibited pinacidil-activated current, and thisinhibition was reduced by chelerythrine (10⁶ M).Acetylcholine (ACh; 10⁵ M) inhibited pinacidil-activatedcurrents, and preincubation of cells with calphostin C(10⁷ M) decreased the effect of ACh. Cells dialyzed withprotein kinase C -isoform (PKC) antibody had normal responses topinacidil, but the effects of PDBu and ACh on K_ATP wereblocked in these cells. Immunofluorescence and Western blots showedexpression of PKC in intact muscles and isolated smooth muscle cellsof the murine proximal colon. These data suggest that PKC regulates K_ATP in colonic muscle cells and that the effects of ACh onK_ATP are largely mediated by PKC. PKC appears to be themajor isozyme that regulates K_ATP in murine colonic myocytes.

     

Elevated Levels of Mercapturic Acids of Acrolein and Crotonaldehyde in the Urine of Chinese Women in Singapore Who Regularly Cook at Home

Lung cancer is unusually common among non-smoking women in Southeastern Asia but the causes of this frequently fatal disease are not well understood. Several epidemiology studies indicate that inhalation of fumes from high temperature Chinese style cooking with a wok may be a cause. Only one previous study investigated uptake of potential toxicants and carcinogens by women who cook with a wok. We enrolled three-hundred twenty-eight non-smoking women from Singapore for this study. Each provided a spot urine sample and answered a questionnaire concerning their cooking habits and other factors. The urine samples were analyzed by liquid chromatography-tandem mass spectrometry for mercapturic acid metabolites of acrolein (3-hydroxypropylmercapturic acid), crotonaldehyde (3-hydroxy-1-methylpropylmercapturic acid), and benzene (S-phenylmercapturic acid), accepted biomarkers of uptake of these toxic and carcinogenic compounds. We observed statistically significant effects of wok cooking frequency on levels of 3-hydroxypropylmercapturic acid and 3-hydroxy-1-methylpropylmercapturic acid, but not S-phenylmercapturic acid. Women who cooked greater than 7 times per week had a geometric mean of 2600 (95% CI, 2189-3090) pmol/mg creatinine 3-hydroxypropylmercapturic acid compared to 1901 (95% CI, 1510-2395) pmol/mg creatinine when cooking less than once per week (P for trend 0.018). The corresponding values for 3-hydroxy-1-methylpropylmercapturic acid were 1167 (95% CI, 1022-1332) and 894 (95% CI, 749-1067) pmol/mg creatinine (P for trend 0.008). We conclude that frequent wok cooking leads to elevated exposure to the toxicants acrolein and crotonaldehyde, but not benzene. Kitchens should be properly ventilated to decrease exposure to potentially toxic and carcinogenic fumes produced during Chinese style wok cooking.     

High-Density Dielectrophoretic Microwell Array for Detection,Capture, and Single-Cell Analysis of Rare Tumor Cells in Peripheral Blood

Development of a reliable platform and workflow to detect and capture a small number of mutation-bearing circulating tumor cells (CTCs) from a blood sample is necessary for the development of noninvasive cancer diagnosis. In this preclinical study, we aimed to develop a capture system for molecular characterization of single CTCs based on high-density dielectrophoretic microwell array technology. Spike-in experiments using lung cancer cell lines were conducted. The microwell array was used to capture spiked cancer cells, and captured single cells were subjected to whole genome amplification followed by sequencing. A high detection rate (70.2%–90.0%) and excellent linear performance (R² = 0.8189–0.9999) were noted between the observed and expected numbers of tumor cells. The detection rate was markedly higher than that obtained using the CellSearch system in a blinded manner, suggesting the superior sensitivity of our system in detecting EpCAM− tumor cells. Isolation of single captured tumor cells, followed by detection of EGFR mutations, was achieved using Sanger sequencing. Using a microwell array, we established an efficient and convenient platform for the capture and characterization of single CTCs. The results of a proof-of-principle preclinical study indicated that this platform has potential for the molecular characterization of captured CTCs from patients.     

Intracellular colocalization of HAP1/STBs with steroid hormone receptors and its enhancement by a proteasome inhibitor

The stigmoid body (STB) is a cytoplasmic inclusion containing huntingtin-associated protein 1 (HAP1), and HAP1/STB formation is induced by transfection of the HAP1 gene into cultured cells. In the present study, we examined the intracellular colocalization of HAP1/STBs with steroid hormone receptors (SHRs), including the androgen receptor (AR), estrogen receptor, glucocorticoid receptor (GR), and mineralocorticoid receptor, in COS-7 cells cotransfected with HAP1 and each receptor. We found that C-terminal ligand-binding domains of all SHRs had potential for colocalization with HAP1/STBs, whereas only AR and GR were clearly colocalized with HAP1/STBs when each full-length SHR was coexpressed with HAP1. In addition, it appeared that HAP1/STBs did not disrupt GR and AR functions because the receptors on HAP1/STBs maintained nuclear translocation activity in response to their specific ligands. When the cells were treated with a proteasome inhibitor, GR and AR localized outside HAP1/STBs translocated into the nucleus, whereas the receptors colocalized with HAP1/STBs persisted in their colocalization even after treatment with their ligands. Therefore, HAP1/STBs may be involved in cytoplasmic modifications of the nuclear translocation of GR and AR in a ubiquitin–proteasome system.     

Studies of the Active Principles of Leucothoe grayana MAX.

Amides, IVa and IVb, which were derived from Grayanotoxin-II reacted very easily under a mild acidic condition to give a product, the structure of which has been established to be Va.     

Gastrointestinal Colonization of Fungi

The human gastrointestinal tract is colonized with trillions of commensal microbes, and disturbances in the equilibrium of the gut microbiota have now been shown to be associated with a number of human diseases. Fungi, particularly Candida spp., are normal, harmless residents of the human gut, but in certain instances can cause invasive infections and inflammatory disorders. This paper will review the fungal diversity in the human gut, host and fungal factors that regulate GI colonization, and how these factors play into the pathogenesis of human disease.