Molecular basis for plasma membrane recruitment of PI4KA by EFR3.

The lipid kinase phosphatidylinositol 4 kinase III alpha (PI4KIIIa/PI4KA) is a master regulator of the lipid composition and asymmetry of the plasma membrane. PI4KA exists primarily in a heterotrimeric complex with its regulatory proteins TTC7 and FAM126. Fundamental to PI4KA activity is its targeted recruitment to the plasma membrane by the lipidated proteins EFR3A and EFR3B. Here, we report a cryo-EM structure of the C-terminus of EFR3A bound to the PI4KA-TTC7B-FAM126A complex, with extensive validation using both hydrogen deuterium exchange mass spectrometry (HDX-MS), and mutational analysis. The EFR3A C-terminus undergoes a disorder-order transition upon binding to the PI4KA complex, with an unexpected direct interaction with both TTC7B and FAM126A. Complex disrupting mutations in TTC7B, FAM126A, and EFR3 decrease PI4KA recruitment to the plasma membrane. Multiple post-translational modifications and disease linked mutations map to this site, providing insight into how PI4KA membrane recruitment can be regulated and disrupted in human disease.

Non-vesicular phosphatidylinositol transfer plays critical roles in defining organelle lipid composition.

Phosphatidylinositol (PI) is the precursor lipid for the minor phosphoinositides (PPIns), which are critical for multiple functions in all eukaryotic cells. It is poorly understood how phosphatidylinositol, which is synthesized in the ER, reaches those membranes where PPIns are formed. Here, we used VT01454, a recently identified inhibitor of class I PI transfer proteins (PITPs), to unravel their roles in lipid metabolism, and solved the structure of inhibitor-bound PITPNA to gain insight into the mode of inhibition. We found that class I PITPs not only distribute PI for PPIns production in various organelles such as the plasma membrane (PM) and late endosomes/lysosomes, but that their inhibition also significantly reduced the levels of phosphatidylserine, di- and triacylglycerols, and other lipids, and caused prominent increases in phosphatidic acid. While VT01454 did not inhibit Golgi PI4P formation nor reduce resting PM PI(4,5)P2 levels, the recovery of the PM pool of PI(4,5)P2 after receptor-mediated hydrolysis required both class I and class II PITPs. Overall, these studies show that class I PITPs differentially regulate phosphoinositide pools and affect the overall cellular lipid landscape.

Luminescence Studies on Dy3+ Doped Calcium Aluminum Borosilicate (CABS) Glasses for White Light Emission and Applications in w-LEDs.

Dy3+ doped calcium aluminum borosilicate (CABS) glasses have been synthesized via quick melt quench technique. CABS: xDy3+ glasses (x = 0.1, 0.5, 1, 1.5 and 2 mol%) were subjected to various morphological and photoluminescence studies. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to study the structural and bonding nature of the undoped glass. The excitation spectra of Dy3+ doped CABS glasses under 574 nm emission show many sharp peaks amongst which the transition from 6H15/2 → 6P7/2 (351 nm) had the highest intensity. Under 351 nm excitation, glasses exhibit sharp peaks in the blue, yellow and red regions corresponding to the transitions 4F9/2 → 6H15/2, 6H13/2, 6H11/2 and 6H9/2 respectively. The dipole-dipole nature of the interaction between the Dy3+ ions is confirmed via Dexter theory and Inokuti-Hirayama (I-H) model. CIE coordinates estimated from the emission profiles of these glasses under 351 nm excitation fall in the white region. Considering that these glasses exhibit sharp visible emission under UV excitation, have stable yellow to blue (Y/B) ratios and fast decays with intense energy transfers, we propose to utilise these glasses for white light generation and other white light LED (w-LED) and solid-state lighting (SSL) applications.

Thermally stable Sm3+ -doped alkali zinc alumino borosilicate (AZABS) glass for warm white light generation and w-LED applications.

Samarium ion (Sm3+ )-doped alkali zinc alumino borosilicate (AZABS) glass was synthesized via quick melt quench technique. Various spectroscopic studies like optical absorption, photoluminescence (PL) emission, PL excitation, temperature-dependent PL and PL decay kinetics were performed on the as prepared glass system. Under 402 nm excitation, three sharp bands at wavelengths 563, 599 and 645 nm corresponding to transitions 4 G5/2 → 6 H5/2 , 6 H7/2 and 6 H9/2 , respectively, can be seen in the PL emission spectra. The 0.25 mol% Sm3+ glass has the highest intensity for these emissions. The lanthanide interaction in the glass matrix is dipole-dipole in nature as was proven from Dexter's analysis. The direct bandgap of 0.25 mol% Sm3+ -doped AZABS glass was calculated to be 2.88 eV. The lifetimes of the as prepared glass range from 1.93 ms for the lowest concentration of Sm3+ to 0.75 ms for the highest. From temperature dependent PL studies, the activation energy for 0.25 mol% Sm3+ -doped AZABS glass was found to be 0.19 eV which shows high thermal stability of this glass. We propose to utilize these Sm3+ -doped AZABS glasses for white-light emitting diodes (w-LEDs) and solid-state lighting (SSL) applications.

Acute salt stress differentially modulates nitrate reductase expression in contrasting salt responsive rice cultivars.

Salt stress response includes alteration in the activity of various important enzymes in plants. Nitrate reductase (NR) is one of the known enzyme affected by salt stress. In this study, contrasting salt responsive cultivars (CVS) (IR64-sensitive and CSR 36-tolerant) were considered to study the regulation of NR genes under salt stress conditions. Using Arabidopsis genes Nia1 and Nia2, three different NR genes were identified in rice and their expression study was conducted. Under stress condition, salt-sensitive CVS (IR64) showed a decrease in NR activity under in vitro and in vivo conditions, whereas tolerant CVS showed an increase in NR activity. Different trends for NR activity in contrasting genotype are explained by the variable number of GATA element in the upstream region of the NR gene. This variation of NR activity in contrasting CVS further co-relates with the transcript level of NR genes. The transcript level of three different NR genes also evidenced the effect of CREs in gene regulation. Promoter (1-kb upstream region) of different NR genes contained different abiotic stress-responsive CREs, which explain the differential behavior of these genes towards the abiotic stress. Overall, this study concludes the role of CREs in the regulation of NR gene and indicates the importance of transcriptional control of NR activity under stress condition. This is the first type of report that highlights the role of the regulatory mechanism of NR genes under salt stress condition.

Antiplasmodial potential and quantification of aloin and aloe-emodin in Aloe vera collected from different climatic regions of India.

BACKGROUND: In this study, Aloe vera samples were collected from different climatic regions of India. Quantitative HPTLC (high performance thin layer chromatography) analysis of important anthraquinones aloin and aloe-emodin and antiplasmodial activity of crude aqueous extracts was done to estimate the effects of these constituents on antiplasmodial potential of the plant. METHODS: HPTLC system equipped with a sample applicator Linomat V with CAMAG sample syringe, twin rough plate development chamber (20 x 10 cm), TLC Scanner 3 and integration software WINCATS 1.4.8 was used for analysis of aloin and aloe-emodin amount. The antiplasmodial activity of plant extracts was assessed against a chloroquine (CQ) sensitive strain of P. falciparum (MRC-2). Minimum Inhibitory Concentration (MIC) of aqueous extracts of selected samples was determined according to the World Health Organization (WHO) recommended method that was based on assessing the inhibition of schizont maturation in a 96-well microtitre plate. EC (effective concentration) values of different samples were observed to predict antiplasmodial potential of the plant in terms of their climatic zones. RESULTS: A maximum quantity of aloin and aloe-emodin i.e. 0.45 and 0.27 mg/g respectively was observed from the 12 samples of Aloe vera. The inhibited parasite growth with EC50 values ranging from 0.289 to 1056 µg/ml. The antiplasmodial EC50 value of positive control Chloroquine was observed 0.034 µg/ml and EC50 values showed by aloin and aloe-emodin was 67 µg/ml and 22 µg/ml respectively. A positive correlation was reported between aloin and aloe-emodin. Antiplasmodial activity was increased with increase in the concentration of aloin and aloe-emodin. The quantity of aloin and aloe-emodin was decreased with rise in temperature hence it was negatively correlated with temperature. CONCLUSIONS: The extracts of Aloe vera collected from colder climatic regions showed good antiplasmodial activity and also showed the presence of higher amount of aloin and aloe-emodin in comparison to collected from warmer climatic sites. Study showed significant correlation between quantities of both the anthraquinones used as marker compounds and EC50 values of the different Aloe vera extracts. Although, both the anthraquinones showed less antiplasmodial potential in comparison to crude extracts of different Aloe vera samples. Diverse climatic factors affect the quantity of tested compounds and antiplasmodial potential of the plant in different Aloe vera samples.