Intestinal TMEM16A control luminal chloride secretion in a NHERF1 dependent manner

TMEM16A (Transmembrane protein 16A or Anoctamin1) is a calcium-activated chloride channel.(CaCC),that exerts critical roles in epithelial secretion. However, its localization, function, and regulation in intestinal chloride (Cl^?) secretion remain obscure. Here, we show that TMEM16A protein abundance correlates with Cl^? secretion in different regions of native intestine activated by the Ca²⁺-elevating muscarinic agonist carbachol (CCH). Basal, as well as both cAMP- and CCH-stimulated Isc, was largely reduced in Ano1 ± mouse intestine. We found CCH was not able to increase Isc in the presence of apical to serosal Cl^? gradient, strongly supporting TMEM16A as primarily a luminal Cl^? channel. Immunostaining demonstrated apical localization of TMEM16A where it colocalized with NHERF1 in mouse colonic tissue. Cellular depletion of NHERF1 in human colonic T84 cells caused a significant reduction of both cAMP- and CCH-stimulated Isc. Immunoprecipitation experiments revealed that NHERF1 forms a complex with TMEM16A through a PDZ-based interaction. We conclude that TMEM16A is a luminal Cl^? channel in the intestine that functionally interacts with CFTR via PDZ-based interaction of NHERF1 for efficient and specific cholinergic stimulation of intestinal Cl^? secretion.     

Biophysical properties of the isolated spike protein binding helix of human ACE2

The entry of the severe acute respiratory syndrome coronavirus 2 virus in human cells is mediated by the binding of its surface spike protein to the human angiotensin-converting enzyme 2 (ACE2) receptor. A 23-residue long helical segment (SBP1) at the binding interface of human ACE2 interacts with viral spike protein and therefore has generated considerable interest as a recognition element for virus detection. Unfortunately, emerging reports indicate that the affinity of SBP1 to the receptor-binding domain of the spike protein is much lower than that of the ACE2 receptor itself. Here, we examine the biophysical properties of SBP1 to reveal factors leading to its low affinity for the spike protein. Whereas SBP1 shows good solubility (solubility > 0.8 mM), circular dichroism spectroscopy shows that it is mostly disordered with some antiparallel β-sheet content and no helicity. The helicity is substantial (>20%) only upon adding high concentrations (≥20% v/v) of 2,2,2-trifluoroethanol, a helix promoter. Fluorescence correlation spectroscopy and single-molecule photobleaching studies show that the peptide oligomerizes at concentrations >50 nM. We hypothesized that mutating the hydrophobic residues (F28, F32, and F40) of SBP1, which do not directly interact with the spike protein, to alanine would reduce peptide oligomerization without affecting its spike binding affinity. Whereas the mutant peptide (SBP1^mod) shows substantially reduced oligomerization propensity, it does not show improved helicity. Our study shows that the failure of efforts, so far, to produce a short SBP1 mimic with a high affinity for the spike protein is not only due to the lack of helicity but is also due to the heretofore unrecognized problem of oligomerization.     

Physio-biochemical and molecular assessment of Iron (Fe2+) toxicity responses in contrasting indigenous aromatic Joha rice cultivars of Assam,India

Iron (Fe) toxicity is one of the major abiotic stresses which limits the yield of lowland rice. This study aims to investigate the physiological, biochemical, and molecular aspects of two contrasting aromatic Joha rice, viz., Keteki and Kola Joha of Assam. Oxidative damage caused due to Fe²⁺ toxicity was quantitatively determined. Fe²⁺ toxicity in the growth medium increases the level of ROS and anti-oxidative enzyme activity. Along with the aforementioned damage caused due to Fe²⁺ toxicity, chlorophyll content decreases in both the rice varieties. Detection of Fe³⁺ and Fe²⁺ was also conducted by Perls’ Prussian and Turnbull blue method, respectively. In addition, spectrophotometric quantification of Fe²⁺ was determined by 2, 2′-Bipyridyl (Bpy). Above 2.5 mM, Fe²⁺ toxicity was found to be lethal in rice seedlings affecting their total growth and biomass. Gene expression analysis of iron-regulated transporter 1 (OsIRT1), Yellow Stripe-Like 15 (OsYSL15), and ferritin 1 (OsFer1) revealed the differential gene expression over a time period of Fe²⁺ toxicity. Our study suggested that the different parameters which are considered here can be helpful for the better understanding of how aromatic Joha rice performed under Fe²⁺ toxicity which can also help to reveal broader aspects that how gene players are involved in the iron homeostasis mechanism in Joha rice in coming future.

     

In vitro evaluation of antioxidant and antibacterial properties of supercritical CO2 extracted essential oil from clove bud (Syzygium aromaticum)

Journal of Plant Biochemistry and Biotechnology - The antioxidant and antimicrobial activity of the essential oil extracted from Syzygium aromaticum was investigated. Extraction of oil was carried...     

Treatment of phenolics containing synthetic wastewater in an internal loop airlift bioreactor (ILALR) using indigenous mixed strain of Pseudomonas sp. under continuous mode of operation

The scope of this study is to evaluate the performance of internal loop airlift bioreactor (ILALR) in treating synthetic wastewater containing phenol and m-cresol, in single and multi component systems. The microbe utilized in the process was an indigenous mixed strain of Pseudomonas sp. isolated from a wastewater treatment plant. The reactor was operated at both lower and higher hydraulic retention times (HRTs) i.e., 4.1 and 8.3 h, respectively, by providing an inlet feed flow rate of 5 and 10 mL/min. Shock loading experiments were also performed up to a maximum concentration of 800 mg/L for phenol at 8.3 h HRT and 500 mg/L for m-cresol at 4.1 h HRT. The study showed complete degradation of both phenol and m-cresol, when they were degraded individually at a HRT of 8.3 h. Experiments with both phenol and m-cresol present as mixtures were performed based on the 2² full factorial design of experiments.     

Localization and thyroid hormone influenced expression of collagen II in ovarian tissue.

Collagen type II (Col II), one of the main components of the hyaline cartilage, is a member of the fibril-forming collagen family. Due to its amino acid composition, the extent of lysine hydroxylation of Col II is much higher than that of other fibril forming collagens. Since lysyl hydroxylase isoforms are less synthesized in hypothyroid ovarian tissue, Col II level is expected to be reduced here and contribute to the degradation of ovarian ECM in this condition. As there was no previous report, we have demonstrated Col II expression in rat ovary. Col2A1 mRNA shares significant part of the total collagens in ovary as shown by the relative expression of the major collagen genes present in this tissue. It has also been shown that Col II is down regulated in hypothyroid ovarian tissue and its expression is increased upon stimulation by thyroid hormone (T(3)). To know whether less Col II in hypothyroid ovarian tissue is due to less synthesis of the protein or its increased rate of degradation is also involved in it, we demonstrated the status of Collagen - degrading Matrix Metalloproteinases in this condition and found up regulation of MMP-1, -8 and -13 in hypothyroid rat ovary. The present study shows the reduced Col II expression in hypothyroid rat ovary, with the concomitant increase in Col II degradation. This information will be useful for further studies on reproductive disorders.     

Designing synthetic materials to control stem cell phenotype

The micro-environment in which stem cells reside regulates their fate, and synthetic materials have recently been designed to emulate these regulatory processes for various medical applications. Ligands inspired by the natural extracellular matrix, cell-cell contacts, and growth factors have been incorporated into synthetic materials with precisely engineered density and presentation. Furthermore, material architecture and mechanical properties are material design parameters that provide a context for receptor-ligand interactions and thereby contribute to fate determination of uncommitted stem cells. Although significant progress has been made in biomaterials development for cellular control, the design of more sophisticated and robust synthetic materials can address future challenges in achieving spatiotemporal control of cellular phenotype and in implementing histocompatible clinical therapies.     

Specificity of TRAF3 in its negative regulation of the noncanonical NF-kappa B pathway

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are critical signaling adaptors downstream of many receptors in the TNF receptor and interleukin-1 receptor/Toll-like receptor superfamilies. Whereas TRAF2, 5, and 6 are activators of the canonical NF-kappaB signaling pathway, TRAF3 is an inhibitor of the noncanonical NF-kappaB pathway. The contribution of the different domains in TRAFs to their respective functions remains unclear. To elucidate the structural and functional specificities of TRAF3, we reconstituted TRAF3-deficient cells with a series of TRAF3 mutants and assessed their abilities to restore TRAF3-mediated inhibition of the noncanonical NF-kappaB pathway as measured by NF-kappaB-inducing kinase (NIK) protein levels and processing of p100 to p52. We found that a structurally intact RING finger domain of TRAF3 is required for inhibition of the noncanonical NF-kappaB pathway. In addition, the three N-terminal domains, but not the C-terminal TRAF domain, of the highly homologous TRAF5 can functionally replace the corresponding domains of TRAF3 in suppression of the noncanonical NF-kappaB pathway. This functional specificity correlates with the specific binding of TRAF3, but not TRAF5, to the previously reported TRAF3 binding motif in NIK. Our studies suggest that both the RING finger domain activity and the specific binding of the TRAF domain to NIK are two critical components of TRAF3 suppression of NIK protein levels and the processing of p100 to p52.