Discovery of pyrazolopyrimidine derivatives as novel inhibitors of ataxia telangiectasia and rad3 related protein (ATR)

The ATR pathway is a critical mediator of the replication stress response in cells. In aberrantly proliferating cancer cells, this pathway can help maintain sufficient genomic integrity for cancer cell progression. Herein we describe the discovery of 19, a pyrazolopyrimidine-containing inhibitor of ATR via a strategic repurposing of compounds targeting PI3K.     

Identification of an atypical calcium-dependent calmodulin binding site on the C-terminal domain of GluN2A

N-methyl-d-aspartate (NMDA) receptors are calcium-permeable ion channels assembled from four subunits that each have a common membrane topology. The intracellular carboxyl terminal domain (CTD) of each subunit varies in length, is least conserved between subunits, and binds multiple intracellular proteins. We defined a region of interest in the GluN2A CTD, downstream of well-characterized membrane-proximal motifs, that shares only 29% sequence similarity with the equivalent region of GluN2B. GluN2A (amino acids 875–1029) was fused to GST and used as a bait to identify proteins from mouse brain with the potential to bind GluN2A as a function of calcium. Using mass spectrometry we identified calmodulin as a calcium-dependent GluN2A binding partner. Equilibrium fluorescence spectroscopy experiments indicate that Ca²⁺/calmodulin binds GluN2A with high affinity (5.2 ± 2.4 nM) in vitro. Direct interaction of Ca²⁺/calmodulin with GluN2A was not affected by disruption of classic sequence motifs associated with Ca²⁺/calmodulin target recognition, but was critically dependent upon Trp-1014. These findings provide new insight into the potential of Ca²⁺/calmodulin, previously considered a GluN1-binding partner, to influence NMDA receptors by direct association.     

Solution structure of the MAPK phosphatase PAC-1 catalytic domain. Insights into substrate-induced enzymatic activation of MKP

Inactivation of mitogen-activated protein kinases (MAPKs) by MAPK phosphatases (MKPs) is accomplished via substrate-induced activation of the latter enzymes; however, the structural basis for the underlying mechanism remains elusive. Here, we report the three-dimensional solution structure of the C-terminal phosphatase domain of the prototypical MKP PAC-1, determined when bound to phosphate. Structural and biochemical analyses reveal unique active site geometry of the enzyme important for binding to phosphorylated threonine and tyrosine of MAPK ERK2. Our study further demonstrates that the dynamic interaction between the N-terminal kinase binding domain and the C-terminal phosphatase domain of an MKP is directly coupled to MAPK-induced conformational change of the phosphatase active site, which is essential for eliciting its full enzymatic activity.     

Review: role of carbon sources for in vitro plant growth and development

In vitro plant cells, tissues and organ cultures are not fully autotrophic establishing a need for carbohydrates in culture media to maintain the osmotic potential, as well as to serve as energy and carbon sources for developmental processes including shoot proliferation, root induction as well as emission, embryogenesis and organogenesis, which are highly energy demanding developmental processes in plant biology. A variety of carbon sources (both reducing and non-reducing) are used in culture media depending upon genotypes and specific stages of growth. However, sucrose is most widely used as a major transport-sugar in the phloem sap of many plants. In micropropagation systems, morphogenetic potential of plant tissues can greatly be manipulated by varying type and concentration of carbon sources. The present article reviews the past and current findings on carbon sources and their sustainable utilization for in vitro plant tissue culture to achieve better growth rate and development.     

Aquisphaera insulae sp. nov., a new member in the family Isosphaeraceae,isolated from the floating island of Loktak lake and emended description of the genus Aquisphaera

Antonie van Leeuwenhoek - Strain JC669T was isolated from a floating island of Loktak lake, Manipur, India and shares the highest 16S rRNA gene sequence identity with Aquisphaera giovannonii OJF2T....     

Oxidative stress alters renal D1 and AT1 receptor functions and increases blood pressure in old rats

Aging is associated with an increase in oxidative stress and blood pressure (BP). Renal dopamine D1 (D1R) and angiotensin II AT1 (AT1R) receptors maintain sodium homeostasis and BP. We hypothesized that age-associated increase in oxidative stress causes altered D1R and AT1R functions and high BP in aging. To test this, adult (3 mo) and old (21 mo) Fischer 344 × Brown Norway F1 rats were supplemented without/with antioxidant tempol followed by determining oxidative stress markers (urinary antioxidant capacity, proximal tubular NADPH-gp91phox, and plasma 8-isoprostane), D1R and AT1R functions, and BP. The D1R and AT1R functions were determined by measuring diuretic and natriuretic responses to D1R agonist (SKF-38393; 1 μg·kg(-1)·min(-1) iv) and AT1R antagonist (candesartan; 10 μg/kg iv), respectively. We found that the total urinary antioxidant capacity was lower in old rats, which increased with tempol treatment. In addition, tempol decreased the elevated NADPH-gp91phox and 8-isoprostane levels in old rats. Systolic, diastolic, and mean arterial BPs were higher in old rats and were reduced by tempol. Although SKF-38393 produced diuresis in both adult and old rats, urinary sodium excretion (UNaV) increased only in adult rats. While candesartan increased diuresis and UNaV in adult and old rats, the magnitude of response was greater in old rats. Tempol treatment in old rats reduced candesartan-induced increase in diuresis and UNaV. Our results demonstrate that diminished renal D1R and exaggerated AT1R functions are associated with high BP in old rats. Furthermore, oxidative stress may cause altered renal D1R and AT1R functions and high BP in old rats.