Intracellular lipidation of newly synthesized apolipoprotein A-I in primary murine hepatocytes

Hepatocytes, which are the main site of apolipoprotein (apo)A-I and ATP-binding cassette transporter A1 (ABCA1) expression, are also the main source of circulating high density lipoprotein. Here we have characterized the intracellular lipidation of newly synthesized apoA-I, in primary hepatocytes cultured with [3H]choline to label choline-phospholipids, low density lipoprotein-[3H]cholesterol to label the cell surface, or [3H]mevalonate to label de novo synthesized cholesterol. Phospholipidation of apoA-I is significant and most evident in endoplasmic reticulum (ER) and medial Golgi, both in the lumen and on the membrane fractions of the ER and medial Golgi. In the presence of cycloheximide, endogenous apoA-I is substantially phospholipidated intracellularly but acquires some additional lipid after export out of the cell. In cells labeled with low density lipoprotein-[3H]cholesterol, intracellular cholesterol lipidation of apoA-I is entirely absent, but the secreted apoA-I rapidly accumulates cholesterol after secretion from the cell in the media. On the other hand, de novo synthesized cholesterol can lipidate apoA-I intracellularly. We also showed the interaction between apoA-I and ABCA1 in ER and Golgi fractions. In hepatocytes lacking ABCA1, lipidation by low density lipoprotein-cholesterol was significantly reduced at the plasma membrane, phospholipidation and lipidation by de novo synthesized sterols were both reduced in Golgi compartments, whereas ER lipidation remained mostly unchanged. Therefore, the early lipidation in ER is ABCA1 independent, but in contrast, the lipidation of apoA-I in Golgi and at the plasma membrane requires ABCA1. Thus, we demonstrated that apoA-I phospholipidation starts early in the ER and is partially dependent on ABCA1, with the bulk of lipidation by phospholipids and cholesterol occurring in the Golgi and at the plasma membrane, respectively. Finally, we showed that the previously reported association of newly synthesized apoA-I and apoB (Zheng, H., Kiss, R. S., Franklin, V., Wang, M. D., Haidar, B., and Marcel, Y. L. (2005) J. Biol. Chem. 280, 21612-21621) occurs after secretion at the cell surface.     

Computational analysis of position-dependent disorder content in DisProt database

A bioinformatics analysis of disorder content of proteins from the DisProt database has been performed with respect to position of disordered residues.Each protein chain was divided into three parts:N-and C-terminal parts with each containing 30 amino acid(AA) residues and the middle region containing the remaining AA residues.The results show that in terminal parts,the percentage of disordered AA residues is higher than that of all AA residues(17% of disordered AA residues and 11% of all).We analyzed the percentage of disorder for each of 20 AA residues in the three parts of proteins with respect to their hydropathy and molecular weight.For each AA,the percentage of disorder in the middle part is lower than that in terminal parts which is comparable at the two termini.A new scale of AAs has been introduced according to their disorder content in the middle part of proteins:CIFWMLYHRNVTAGQDSKEP.All big hydrophobic AAs are less frequently disordered,while almost all small hydrophilic AAs are more frequently disordered.The results obtained may be useful for construction and improving predictors for protein disorder.     

Climate change,biological invasions,and the shifting distribution of Mediterranean fishes: A large‐scale survey based on local ecological knowledge

Climate change and biological invasions are rapidly reshuffling species distribution, restructuring the biological communities of many ecosystems worldwide. Tracking these transformations in the marine environment is crucial, but our understanding of climate change effects and invasive species dynamics is often hampered by the practical challenge of surveying large geographical areas. Here, we focus on the Mediterranean Sea, a hot spot for climate change and biological invasions to investigate recent spatiotemporal changes in fish abundances and distribution. To this end, we accessed the local ecological knowledge (LEK) of small‐scale and recreational fishers, reconstructing the dynamics of fish perceived as “new” or increasing in different fishing areas. Over 500 fishers across 95 locations and nine different countries were interviewed, and semiquantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, mostly warm‐adapted species of both native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatial and temporal patterns, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of the shifting distribution of Mediterranean fishes and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macroregional coordination could pave the way for future large‐scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level. This might help local communities to better understand, manage, and adapt to the ongoing biotic transformations driven by climate change and biological invaders.     

Supramolecular Engineering for Formamidinium‐Based Layered 2D Perovskite Solar Cells: Structural Complexity and Dynamics Revealed by Solid‐State NMR Spectroscopy

Perovskite solar cells are one of the most promising photovoltaic technologies, although their molecular level design and stability toward environmental factors remain a challenge. Layered 2D Ruddlesden–Popper perovskite phases feature an organic spacer bilayer that enhances their environmental stability. Here, the concept of supramolecular engineering of 2D perovskite materials is demonstrated in the case of formamidinium (FA) containing A₂FA_n?1Pb_nI_3n+1 formulations by employing (adamantan‐1‐yl)methanammonium (A) spacers exhibiting propensity for strong Van der Waals interactions complemented by structural adaptability. The molecular design translates into desirable structural features and phases with different compositions and dimensionalities, identified uniquely at the atomic level by solid‐state NMR spectroscopy. For A₂FA₂Pb₃I₁₀, efficiencies exceeding 7% in mesoscopic device architectures without any additional treatment or use of antisolvents for ambient temperature film deposition are achieved. This performance improvement over the state‐of‐the‐art FA‐based 2D perovskites is accompanied by high operational stability under humid ambient conditions, which illustrates the utility of the approach in perovskite solar cells and sets the basis for advanced supramolecular design in the future.     

The stage‐regulated HASPB and SHERP proteins are essential for differentiation of the protozoan parasite Leishmania major in its sand fly vector,Phlebotomus papatasi

The stage‐regulated HASPB and SHERP proteins of Leishmania major are predominantly expressed in cultured metacyclic parasites that are competent for macrophage uptake and survival. The role of these proteins in parasite development in the sand fly vector has not been explored, however. Here, we confirm that expression of HASPB is detected only in vector metacyclic stages, correlating with the expression of metacyclic‐specific lipophosphoglycan and providing the first definitive protein marker for this infective sand fly stage. Similarly, SHERP is expressed in vector metacyclics but is also detected at low levels in the preceding short promastigote stage. Using genetically modified parasites lacking or complemented for the LmcDNA16 locus on chromosome 23 that contains the HASP and SHERP genes, we further show that the presence of this locus is essential for parasite differentiation to the metacyclic stage in Phlebotomus papatasi. While wild‐type and complemented parasites transform normally in late‐stage infections, generating metacyclic promastigotes and colonizing the sand fly stomodeal valve, null parasites accumulate at the earlier elongated nectomonad stage of development within the abdominal and thoracic midgut of the sand fly. Complementation with HASPB or SHERP alone suggests that HASPB is the dominant effector molecule in this process.     

Kinetics and mechanism of the substitution reactions of [PtCl(bpma)]<Superscript>+</Superscript>, [PtCl(gly-met-<Emphasis Type="Italic">S,N,N</Emphasis>)] and their aqua analogues with <Emphasis Type="SmallCaps">l</Emphasis>-methionine,glutathione and 5′-GMP

The substitution reactions of [PtCl(bpma)]+, [PtCl(gly-met-S,N,N)], [Pt(bpma)(H(2)O)](2+) and [Pt(gly-met-S,N,N)(H(2)O)](+) [where bpma is bis(2-pyridylmethyl)amine and gly-met-S,N,N is glycylmethionine] with L-methionine, glutathione and guanosine 5'-monophosphate (5'-GMP) were studied in aqueous solutions in 0.10 M NaClO(4) under pseudo-first-order conditions as a function of concentration and temperature using UV-vis spectrophotometry. The reactions of the chloro complexes were followed in the presence of 10 mM NaCl and at pH approximately 5, whereas the reactions of the aqua complexes were studied at pH 2.5. The [PtCl(bpma)]+ complex is more reactive towards the chosen nucleophiles than [PtCl(gly-met-S,N,N)]. Also, the aqua complexes are more reactive than the corresponding chloro complexes. The activation parameters for all the reactions studied suggest an associative substitution mechanism. The reactions of [PtCl(bpma)]+ and [PtCl(gly-met-S,N,N)] with 5'-GMP were studied by using (1)H NMR spectroscopy at 298 K. The pK (a) value of the [Pt(gly-met-S,N,N)(H(2)O)]+ complex is 5.95. Density functional theory calculations (B3LYP/LANL2DZp) show that in all cases guanine coordination to the L(3)Pt fragment (L(3) is terpyridine, bpma, diethylenetriamine, gly-met-S,N,N) is much more favorable than the thioether-coordinated form. The calculations collectively support the experimentally observed substitution of thioethers from Pt(II) complexes by N7-GMP. This study throws more light on the mechanistic behavior of platinum antitumor complexes.     

Combined hormonal contraceptives are associated with minor changes in composition and diversity in gut microbiota of healthy women

Recent human and animal studies have found associations between gut microbiota composition and serum levels of sex hormones, indicating that they could be an important factor in shaping the microbiota. However, little is known about the effect of regular hormonal fluctuations over the menstrual cycle or CHC-related changes of hormone levels on gut microbiota structure, diversity and dynamics. The aim of this study was to investigate the effect of CHCs on human gut microbiota composition. The effect of CHC pill intake on gut microbiota composition was studied in a group of seven healthy pre-menopausal women using the CHC pill, compared to the control group of nine age-matched healthy women that have not used hormonal contraceptives in the 6 months prior to the start of the study. By analysing the gut microbiota composition in both groups during one menstrual cycle, we found that CHC usage is associated with a minor decrease in gut microbiota diversity and differences in the abundance of several bacterial taxa. These results call for further investigation of the mechanisms underlying hormonal and hormonal contraceptive-related changes of the gut microbiota and the potential implications of these changes for women's health.     

A key metabolic integrator,coenzyme A,modulates the activity of peroxiredoxin 5 via covalent modification

Molecular and Cellular Biochemistry - Cisplatin has been extensively used as a chemotherapeutic agent since around 40 years, though its usage is limited due to severe adverse effects like...