Macrophage lipoprotein lipase modulates the development of atherosclerosis but not adiposity

The role of macrophage lipoprotein lipase (LpL) in the development of atherosclerosis and adiposity was examined in macrophage LpL knockout (MLpLKO) mice. MLpLKO mice were generated using cre-loxP gene targeting. Loss of LpL in macrophages did not alter plasma LpL activity or lipoprotein levels. Incubation of apolipoprotein E (ApoE)-deficient β-VLDL with peritoneal macrophages from ApoE knockout mice lacking macrophage LpL (MLpLKO/ApoEKO) led to less cholesteryl ester formation than that found with ApoEKO macrophages. MLpLKO/ApoEKO macrophages had reduced intracellular triglyceride levels, with decreased CD36 and carnitine palmitoyltransferase-1 mRNA levels compared with ApoEKO macrophages, when incubated with VLDL. Although both MLpLKO/ApoEKO and ApoEKO mice developed comparable hypercholesterolemia in response to feeding with a Western-type diet for 12 weeks, atherosclerosis was less in MLpLKO/ApoEKO mice. Epididymal fat mass and gene expression levels associated with inflammation did not differ between the two groups. In conclusion, macrophage LpL plays an important role in the development of atherosclerosis but not adiposity.     

Spatial arrangement of proteins using scCro-tag: application for an in situ enzymatic microbead assay

ABSTRACT

In natural systems, various metabolic reactions are often spatially organized to increase enzyme activity and specificity. Thus, by spatially arranging enzyme molecules in synthetic systems to imitate these natural systems, it is possible to promote a high rate of enzymatic turnover. In this present study, a normal and mutant form of the scCro DNA-binding protein were shown to bind orthogonally to specific recognition sequences under appropriate conditions. Furthermore, these DNA-binding tags were used to establish an enzyme assay system based on the spatial arrangement of transglutaminase and its substrate at the molecular level. Together, the results of the present study suggest that the scCro-tag may be a powerful tool to facilitate the synthetic spatial arrangement of proteins on a DNA ligand.     

Relative sea‐level change regulates organic carbon accumulation in coastal habitats

Because coastal habitats store large amounts of organic carbon (C_org), the conservation and restoration of these habitats are considered to be important measures for mitigating global climate change. Although future sea‐level rise is predicted to change the characteristics of these habitats, its impact on their rate of C_org sequestration is highly uncertain. Here we used historical depositional records to show that relative sea‐level (RSL) changes regulated C_org accumulation rates in boreal contiguous seagrass–saltmarsh habitats. Age–depth modeling and geological and biogeochemical approaches indicated that C_org accumulation rates varied as a function of changes in depositional environments and habitat relocations. In particular, C_org accumulation rates were enhanced in subtidal seagrass meadows during times of RSL rise, which were caused by postseismic land subsidence and climate change. Our findings identify historical analogs for the future impact of RSL rise driven by global climate change on rates of C_org sequestration in coastal habitats.     

CYP26A1 and CYP26C1 cooperatively regulate anterior-posterior patterning of the developing brain and the production of migratory cranial neural crest cells in the mouse

The appropriate regulation of retinoic acid signaling is indispensable for patterning of the vertebrate central nervous system along the anteroposterior (A-P) axis. Although both CYP26A1 and CYP26C1, retinoic acid-degrading enzymes that are expressed at the anterior end of the gastrulating mouse embryo, have been thought to play an important role in central nervous system patterning, the detailed mechanism of their contribution has remained largely unknown. We have now analyzed CYP26A1 and CYP26C1 function by generating knockout mice. Loss of CYP26C1 did not appear to affect embryonic development, suggesting that CYP26A1 and CYP26C1 are functionally redundant. In contrast, mice lacking both CYP26A1 and CYP26C1 were found to manifest a pronounced anterior truncation of the brain associated with A-P patterning defects that reflect expansion of posterior identity at the expense of anterior identity. Furthermore, Cyp26a1-/-Cyp26c1-/- mice fail to produce migratory cranial neural crest cells in the forebrain and midbrain. These observations, together with a reevaluation of Cyp26a1 mutant mice, suggest that the activity of CYP26A1 and CYP26C1 is required for correct A-P patterning and production of migratory cranial neural crest cells in the developing mammalian brain.     

A new membrane-bound cytochrome c works as an electron donor to the photosynthetic reaction center complex in the purple bacterium, Rhodovulum sulfidophilum

A new type of membrane-bound cytochrome c was found in a marine purple photosynthetic bacterium, Rhodovulum sulfidophilum. This cytochrome c was significantly accumulated in cells growing under anaerobic photosynthetic conditions and showed an apparent molecular mass of approximately 100 kDa when purified and analyzed by SDS-PAGE. The midpoint potential of this cytochrome c was 369 mV. Flash-induced kinetic measurements showed that this new cytochrome c can work as an electron donor to the photosynthetic reaction center. The gene coding for this cytochrome c was cloned and analyzed. The deduced molecular mass was nearly equal to 50 kDa. Its C-terminal heme-containing region showed the highest sequence identity to the water-soluble cytochrome c(2), although its predicted secondary structure resembles that of cytochrome c(y). Phylogenetic analyses suggested that this new cytochrome c has evolved from cytochrome c(2). We, thus, propose its designation as cytochrome c(2m). Mutants lacking this cytochrome or cytochrome c(2) showed the same growth rate as the wild type. However, a double mutant lacking both cytochrome c(2) and c(2m) showed no growth under photosynthetic conditions. It was concluded that either the membrane-bound cytochrome c(2m) or the water-soluble cytochrome c(2) work as a physiological electron carrier in the photosynthetic electron transfer pathway of Rvu. sulfidophilum.