Facilitated phospholipid translocation in vesicles and nucleated cells using synthetic small molecule scramblases

Abstract

A series of sixteen synthetic scramblase candidates were prepared from a tris(aminoethyl)amine (TREN) scaffold and evaluated for ability to facilitate translocation of fluorescent phospholipid probes across vesicle membranes and endogenous phosphatidylserine across the plasma membrane of nucleated cells. More than half of the compounds were found to greatly accelerate phospholipid translocation in vesicles. However, they were generally unable to induce large increases in the amount of phosphatidylserine on the surface of nucleated mammalian cells, which contrasts with previous results using erythrocytes. Fluorescence microscopy showed that the synthetic scramblases are rapidly trafficked out of the cell plasma membrane and into the membranes of internal organelles. Future molecular designs of synthetic scramblases should focus on structures that are more amphiphilic, a structural feature that is expected to increase plasma membrane residence time.

Modulating the Primary and Secondary Coordination Spheres within a Series of CoII—OH Complexes

“…22–24 For K 2 [Co II (OH)(H 3 buea)] a DMA/Et 2 O diffusion was used to crystallize the salt instead of DMA-MeCN/Et 2 O diffusion. The metal precursor Co(OAc) 2 was purchased from Sigma Aldrich in ≥ 99% purity and used as received.…”

A Novel Compound Inhibits Reconstituted High-Density Lipoprotein Assembly and Blocks Nascent High-Density Lipoprotein Biogenesis Downstream of Apolipoprotein AI Binding to ATP-Binding Cassette Transporter A1–Expressing Cells

“…Compound 2 also does not exhibit cell toxicity at the doses used (LD 50 > 100 µmol/L). 12 To determine whether compound 1 and 2 inhibit nascent HDL biogenesis, RAW 264.7 cells labeled with [ 3 H]cholesterol and induced to express ABCA1 were pretreated with 10 µmol/L compound 1 for 1 hour or 30 µmol/L compound 2 for 3 hours; thereafter, the pretreatment medium was replaced with fresh medium that contained lipid-free apoAI and the same compound at the same concentration as during the pretreatment, and the cells were allowed to produce nascent HDL for 4 hours. Compound 1 suppressed ABCA1-mediated cholesterol efflux to apoAI by over 70% (Figure 4A).…”

“…Based on the previous observations that compound 1 readily enters the cell and freely disperses among the subcellular membranes,12 it was assumed that all cellular phospholipid was available for bonding with the inhibitor. The dosage of compound 1 was expressed as the ratio of moles of this inhibitor added per cell culture well to moles of cell phospholipid in the same well.…”

“…11 As phospholipid translocases, these compounds turned out to be ineffective in nucleated cells. 12 Nonetheless, we hypothesized that large hydrogen-bonded translocase-phospholipid complexes could interfere with the apoAI-lipid assembly into lipoprotein particles. Here, we show that a representative member of the translocase group, methyl 3α-acetoxy-7α,12α-di[(phenylaminocarbonyl)amino]-5β-cholan-24-oate (referred to in the following as compound 1), inhibits rHDL and nascent HDL formation, causes accumulation of apoAI in ABCA1-expressing cells and thus resolves the final stages of nascent HDL biogenesis into individual steps in cultured cells under normal physiological conditions.…”

Design, synthesis, and testing of an isoquinoline-3-carboxylic-based novel anti-tumor lead

“…Oxidation of 1 with KMnO 4 gave isoquinoline-3-carboxylic acid 2 in 83% yield. Mono-N-Boc-protected TREN 3, obtained from the reaction of TREN with di-tert-butyldicarbonate in 92% yield, 23 To further investigate the therapeutic potential of compound 6, an in vivo anti-tumor activity assay was carried out on S180 tumor bearing mice. Twenty-four hours after implantation, the mice were randomly divided into four experimental groups with 12 in each group.…”