Asymmetry in the lipid affinity of bihelical amphipathic peptides. A structural determinant for the specificity of ABCA1-dependent cholesterol efflux by peptides.

ApoA-I contains a tandem array of amphipathic helices with varying lipid affinity, which are critical in its ability to bind and remove lipids from cells by the ABCA1 transporter. In this study, the effect of asymmetry in the lipid affinity of amphipathic helices in a bihelical apoA-I mimetic peptide, 37pA, on lipid efflux by the ABCA1 transporter was examined. Seven peptide variants of 37pA were produced by substituting a varying number of hydrophobic amino acids for alanine on either one or both helices.

Hepatic ABCG5/G8 overexpression reduces apoB-lipoproteins and atherosclerosis when cholesterol absorption is inhibited.

We previously reported that liver-specific overexpression of ABCG5/G8 in mice is not atheroprotective, suggesting that increased biliary cholesterol secretion must be coupled with decreased intestinal cholesterol absorption to increase net sterol loss from the body and reduce atherosclerosis. To evaluate this hypothesis, we fed low density lipoprotein receptor-knockout (LDLr-KO) control and ABCG5/G8-transgenic (ABCG5/G8-Tg)xLDLr-KO mice, which overexpress ABCG5/G8 only in liver, a Western diet containing ezetimibe to reduce intestinal cholesterol absorption. On this dietary regimen, liver-specific ABCG5/G8 overexpression increased hepatobiliary cholesterol concentration and secretion rates (1.

Neuronal calcium sensor-1 facilitates neuronal exocytosis through phosphatidylinositol 4-kinase.

This work tested the theory that neuronal calcium sensor-1 (NCS-1) has effects on neurotransmitter release beyond its actions on membrane channels. We used nerve-ending preparations where membrane channels are bypassed through membrane permeabilization made by mechanical disruption or streptolysin-O. Nerve ending NCS-1 and phosphatidylinositol 4-kinase (PI4K) are largely or entirely particulate, so their concentrations in nerve endings remain constant after breaching the membrane.

Serum amyloid A binding to CLA-1 (CD36 and LIMPII analogous-1) mediates serum amyloid A protein-induced activation of ERK1/2 and p38 mitogen-activated protein kinases.

Serum amyloid A protein (SAA) is an acute-phase reactant, known to mediate pro-inflammatory cellular responses. This study reports that CLA-1 (CD36 and LIMPII Analogous-1; human orthologue of the Scavenger Receptor Class B Type I (SR-BI)) mediates SAA uptake and downstream SAA signaling. Flow cytometry experiments revealed more than a 5-fold increase of Alexa-488 SAA uptake in HeLa cells stably transfected with CLA-1.

Calcium and chlorpromazine binding to the EF-hand peptides of neuronal calcium sensor-1.

Neuronal calcium sensor-1, a protein of calcium sensor family, is known to have four structural EF-hands. We have synthesised peptides corresponding to all the four EF-hands and studied their conformation and calcium-binding. Our data confirm that the first putative site, a non-canonical one (EF1), does not bind calcium.

Targeting of scavenger receptor class B type I by synthetic amphipathic alpha-helical-containing peptides blocks lipopolysaccharide (LPS) uptake and LPS-induced pro-inflammatory cytokine responses in THP-1 monocyte cells.

Human scavenger receptor class B type I, CLA-1, mediates lipopolysaccharide (LPS) binding and internalization (Vishnyakova, T. G., Bocharov, A.

Abnormal in vivo metabolism of apoB-containing lipoproteins in human apoE deficiency.

The present study was undertaken to elucidate the metabolic basis for the increased remnants and lipoprotein(a) [Lp(a)] and decreased LDL apolipoprotein B (apoB) levels in human apoE deficiency. A primed constant infusion of (13)C(6)-phenylalanine was administered to a homozygous apoE-deficient subject. apoB-100 and apoB-48 were isolated, and tracer enrichments were determined by gas chromatography-mass spectrometry, then kinetic parameters were calculated by multicompartmental modeling.

N-terminal myristoylation regulates calcium-induced conformational changes in neuronal calcium sensor-1.

Neuronal calcium sensor-1 (NCS-1), a Ca(2+)-binding protein, plays an important role in the modulation of neurotransmitter release and phosphatidylinositol signaling pathway. It is known that the physiological activity of NCS-1 is governed by its myristoylation. Here, we present the role of myristoylation of NSC-1 in governing Ca(2+) binding and Ca(2+)-induced conformational changes in NCS-1 as compared with the role in the nonmyristoylated protein.

Hepatic ABCG5 and ABCG8 overexpression increases hepatobiliary sterol transport but does not alter aortic atherosclerosis in transgenic mice.

The individual roles of hepatic versus intestinal ABCG5 and ABCG8 in sterol transport have not yet been investigated. To determine the specific contribution of liver ABCG5/G8 to sterol transport and atherosclerosis, we generated transgenic mice that overexpress human ABCG5 and ABCG8 in the liver but not intestine (liver G5/G8-Tg) in three different genetic backgrounds: C57Bl/6, apoE-KO, and low density lipoprotein receptor (LDLr)-KO. Hepatic overexpression of ABCG5/G8 enhanced hepatobiliary secretion of cholesterol and plant sterols by 1.

Synthetic amphipathic helical peptides promote lipid efflux from cells by an ABCA1-dependent and an ABCA1-independent pathway.

In order to examine the necessary structural features for a protein to promote lipid efflux by the ABCA1 transporter, synthetic peptides were tested on ABCA1-transfected cells (ABCA1 cells) and on control cells. L-37pA, an l amino acid peptide that contains two class-A amphipathic helices linked by proline, showed a 4-fold increase in cholesterol and phospholipid efflux from ABCA1 cells compared to control cells. The same peptide synthesized with a mixture of l and d amino acids was less effective than L-37pA in solubilizing dimyristoyl phosphatidyl choline vesicles and in effluxing lipids.