ATP-binding cassette transporter A7 (ABCA7) is expressed in the brain and has been detected in macrophages, microglia, and neurons. ABCA7 promotes efflux of lipids from cells to apolipoproteins and can also regulate phagocytosis and modulate processing of amyloid precursor protein (APP) to generate the Alzheimer's disease (AD) amyloid-␤ (A␤) peptide. Genome-wide association studies have indicated that ABCA7 single nucleotide polymorphisms confer increased risk for late-onset AD; however, the role that ABCA7 plays in the brain in the AD context is unknown. In the present study, we crossed ABCA7-deficient (A7 Ϫ/Ϫ ) mice with J20 amyloidogenic mice to address this issue. We show that ABCA7 loss doubled insoluble A␤ levels and thioflavine-S-positive plaques in the brain. This was not related to changes in APP processing (assessed by analysis of full-length APP and the APP ␤ C-terminal fragment). Apolipoprotein E regulates cerebral A␤ homeostasis and plaque load; however, the apolipoprotein E concentration was not altered by ABCA7 loss. Spatial reference memory was significantly impaired in both J20 and J20/A7 Ϫ/Ϫ mice compared with wild-type mice; however, there were no cognitive differences between J20 and J20/A7 Ϫ/Ϫ mice. There were also no major differences detected in hippocampal or plaqueassociated microglial/macrophage markers between J20 and J20/A7 Ϫ/Ϫ mice, whereas the capacity for bone marrow-derived macrophages derived from A7 Ϫ/Ϫ mice to take up oligomeric A␤ was reduced by 51% compared with wild-type mice. Our results suggest that ABCA7 plays a role in the regulation of A␤ homeostasis in the brain and that this may be related to altered phagocyte function.

Lipid rafts, defined as cholesterol-and sphingolipid-rich domains, provide specialized lipid environments understood to regulate the organization and function of many plasma membrane proteins. Growing evidence of their existence, protein cargo, and regulation is based largely on the study of isolated lipid rafts; however, the consistency and validity of common isolation methods is controversial. Here, we provide a detailed and direct comparison of the lipid and protein composition of plasma membrane "rafts" prepared from human macrophages by different methods, including several detergent-based isolations and a detergent-free method. We find that detergentbased and detergent-free methods can generate raft fractions with similar lipid contents and a biophysical structure close to that previously found on living cells, even in cells not expressing caveolin-1, such as primary human macrophages. However, important differences between isolation methods are demonstrated. Triton X-100-resistant rafts are less sensitive to cholesterol or sphingomyelin depletion than those prepared by detergent-free methods. Moreover, we show that detergent-based methods can scramble membrane lipids during the isolation process, reorganizing lipids previously in sonication-derived nonraft domains to generate new detergent-resistant rafts. The role of rafts in regulating the biological activities of macrophage plasma membrane proteins may require careful reevaluation using multiple isolation procedures, analyses of lipids, and microscopic techniques. Membranes of eukaryotic cells comprise an immense diversity of lipid species whose purpose and function are poorly understood. The simple model of biological membranes as two-dimensional lipid bilayers has recently been modified to recognize that the self-organizing properties of some lipids drive the formation of specialized domains within cellular membranes (1). Although biological membranes are typically in a fluid (liquid-disordered) state at physiological temperatures, cholesterol and sphingolipids self-associate to form condensed, liquid-ordered domains, or "lipid rafts," within the more fluid "sea" of the rest of the membrane (2-4).Recent interest in lipid rafts comes from the observation that some membrane proteins appear to preferentially partition into raft domains, whereas others are excluded from them. Hence, the structure of lipid rafts, their distribution, and their abundance could control key biological events dependent on the functional organization of the plasma membrane, such as signaling cascades (2), protein and lipid sorting and trafficking (5), cell adhesion and migration (6), entry of viruses (7), bacteria, and toxins (8), and immune responses (9). Lipid rafts have been implicated in a range of macrophage functions, including endotoxin-mediated activation and cytokine production, major histocompatibility complex (MHC) class II antigen presentation (10), phagocytosis (11), and cholesterol export (12). These cells are subject to large variations in cholesterol sta...

We sequenced the entire mitochondrial genome of Abispa ephippium (Hymenoptera: Vespoidea: Vespidae: Eumeninae) and most of the mitochondrial genome of Polistes humilis synoecus (Hymenoptera: Vespoidea: Vespidae: Polistinae). The arrangement of genes differed between the two genomes and also differed slightly from that inferred to be ancestral for the Hymenoptera. The genome organization for both vespids is different from that of all other mitochondrial genomes previously reported. A number of tRNA gene rearrangements were identified that represent potential synapomorphies for a subset of the Vespidae. Analysis of all available hymenopteran mitochondrial genome sequences recovered an uncontroversial phylogeny, one consistent with analyses of other types of data.

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We sequenced most of the mitochondrial (mt) genomes of 2 apocritan taxa: Vanhornia eucnemidarum and Primeuchroeus spp. These mt genomes have similar nucleotide composition and codon usage to those of mt genomes reported for other Hymenoptera, with a total A + T content of 80.1% and 78.2%, respectively. Gene content corresponds to that of other metazoan mt genomes, but gene organization is not conserved. There are a total of 6 tRNA genes rearranged in V. eucnemidarum and 9 in Primeuchroeus spp. Additionally, several noncoding regions were found in the mt genome of V. eucnemidarum, as well as evidence of a sustained gene duplication involving 3 tRNA genes. We also report an inversion of the large and small ribosomal RNA genes in Primeuchroeus spp. mt genome. However, none of the rearrangements reported are phylogenetically informative with respect to the current taxon sample.

Previous studies indicate that apolipoprotein D (apoD) may have a lipid antioxidant function in the brain. We have shown that apoD can reduce free radical-generating lipid hydroperoxides to inert lipid hydroxides in a reaction that involves conversion of surface exposed apoD methione-93 (Met93) residue to Met93-sulfoxide (Met93-SO). One consequence of this reaction is the formation of a stable dimerized form of apoD. As cerebral lipid peroxidation is associated with Alzheimer's disease (AD), in the present study we aimed to assess the possible presence of apoD dimers in postmortem hippocampal and cerebellar tissues derived from a cohort of pathologically defined cases ranging from control to late stage AD. Both soluble and insoluble (requiring guanidine HCl extraction) fractions of tissue homogenates were analyzed for apoD and its dimerized form. We also assessed amyloid-β levels by ELISA and levels of lipid peroxidation by lipid conjugated diene and F2-isoprostane analysis. Our studies reveal a significant association between soluble apoD levels and AD Braak stage whereas apoD dimer formation appears to increase predominantly in the advanced stages of disease. The formation of apoD dimers is closely correlated to lipid conjugated diene levels and occurs in the hippocampus but not in the cerebellum. These results are consistent with the hypothesis that apoD acts as a lipid antioxidant in the brain.

Apolipoprotein D (apoD) is expressed in the brain and levels are increased in affected brain regions in Alzheimer's disease (AD). The role that apoD may play in regulating AD pathology has not been addressed. Here, we crossed both apoD-null mice and Thy-1 human apoD transgenic mice with APP-PS1 amyloidogenic AD mice. Loss of apoD resulted in a nearly 2-fold increase in hippocampal amyloid plaque load, as assessed by immunohistochemical staining. Conversely, transgenic expression of neuronal apoD reduced hippocampal plaque load by approximately 35%. This latter finding was associated with a 60% decrease in amyloid β 1-40 peptide levels, and a 34% decrease in insoluble amyloid β 1-42 peptide. Assessment of β-site amyloid precursor protein cleaving enzyme-1 (BACE1) levels and proteolytic products of amyloid precursor protein and neuregulin-1 point toward a possible association of altered BACE1 activity in association with altered apoD levels. In conclusion, the current studies provide clear evidence that apoD regulates amyloid plaque pathology in a mouse model of AD. Disciplines Medicine and Health Sciences Publication DetailsLi, H., Ruberu, K., Sanz Munoz, S., Jenner, A. M., Spiro, A., Zhao, H., Rassart, E., Sanchez, D., Ganfornina, M. peptide levels, and a 34% decrease in insoluble amyloid-beta 1-42 peptide. Assessment of beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) levels and proteolytic products of amyloid precursor protein and neuregulin-1 point towards a possible association of altered BACE1 activity in association with altered apoD levels. In conclusion, the current studies provide clear evidence that apoD regulates amyloid plaque pathology in a mouse model of AD.

Apolipoprotein-E (apoE) is a glycoprotein highly expressed in the brain, where it appears to play a role in lipid transport, b-amyloid clearance, and neuronal signaling. ApoE proteolytic fragments are also present in the brain, but the enzymes responsible for apoE fragmentation are unknown, and the biological activity of specific apoE fragments remains to be determined. Here we utilised SK-N-SH neuroblastoma cells differentiated into neurons with all-trans retinoic acid (ATRA) to study extracellular apoE proteolysis. ApoE fragments were detectable in culture supernatants after 3 days, and their levels were increased for up to 9 days in the presence of ATRA. The concentration of apoE fragments was positively correlated with levels of the neuronal maturation markers (PSD95 and SMI32). The most abundant apoE fragments were 25 kDa and 28 kDa N-terminal fragments that both contained sialylated glycosylation and bound to heparin. We detected apoE fragments only in the extracellular milieu and not in cell lysates, suggesting that an extracellular protease contributes to apoE fragmentation.Of note, siRNA-mediated knockdown of high-temperature requirement serine peptidase A1 (HtrA1) and a specific HtrA1 inhibitor reduced apoE 25 kDa fragment formation by 41% and 86%, respectively. Recombinant 25-kDa fragment apoE and full-length apoE both stimulated neuritogenesis in vitro, increasing neuroblastoma neurite growth by more than 2-fold over a 6-day period. This study provides a cellular model for assessing apoE proteolysis, indicates that HtrA1 regulates apoE 25-kDa fragment formation under physiological conditions, and reveals a new neurotrophic function for the apoE 25-kDa fragment. ________________________________________