Quantifying membrane permeability of amphotericin B ion channels in single living cells.

Recently, the structure-function relationships between amphotericin B (AmB) and ergosterol have been solved using synthetic techniques that require a mycosamine-mediated direct binding interaction between AmB and ergosterol to form AmB ion channels. However, studies to directly probe the AmB-induced membrane permeability changes have not been conducted. In the present work, we investigate the following fundamental question: does AmB induce concentration- and time-dependent permeability changes across ergosterol-containing membranes? Herein, we employ fluorescent dyes of known average diameter to quantify the diameters of AmB ion channels. In addition, we take a single-particle tracking approach to define the intracellular microrheology in the absence and presence of AmB ion channels. Present results show that increasing AmB concentration tends to increase the preferential accumulation of AmB ion channels in the presence of the excess membrane-embedded ergosterol. We found that AmB induces time-dependent membrane permeability; increases approaching 50% in both the velocity fluctuations and diffusion coefficients of vesicles occur on the same time scale as the efflux of potassium ions (≅30min). Furthermore, we propose a two-dimensional, semi-regular tessellation model to geometrically assess the pore size of the AmB ion channels in response to the AmB dose. This approach offers one possibility for the design of AmB ion channels with tunable aqueous pore size, which could provide an opportunity to replace damaged membrane water channels of the aquaporin family in future applications.

Associations of melatonin receptor gene polymorphisms with Graves' disease.

BACKGROUND: Melatonin plays an important role in immunity and has been linked to autoimmune diseases. Possible associations of single-nucleotide polymorphisms (SNPs) of melatonin receptor type 1A (MTNR1A) and 1B (MTNR1B), with autoimmune thyroid disease in an ethnic Chinese (i.e., Taiwanese) population were examined. MATERIALS AND METHODS: Totally, 83 Hashimoto's thyroiditis patients, 319 Graves' disease (GD), and 369 controls were recruited. Three SNPs (rs6553010, rs13140012, and rs2119882) of MTNR1A and three SNPs (rs1387153, rs10830963, and rs1562444) of MTNR1B were genotyped. RESULTS: There were a reduced frequency of the C allele of rs2119882 and a reduced percentage of the CC+CT genotype in the GD group compared to the control group (p = 0.039, odds ratio (OR) = 0.79, 95% confidence interval (CI) = 0.63~0.99, and p = 0.032, OR = 0.72, 95% CI = 0.53~0.97, respectively). There was a significant difference in the percentage of the AT haplotype of the combination of rs13140012 and rs2119882 between the GD and control groups (p = 0.010, OR = 1.34, 95% CI = 1.07~1.67). In addition, there were significant associations of anti-thyroid peroxidase antibody titers with rs13140012 and rs2119882, and the AATT genotype of the combination of rs13140012 and rs2119882 (p = 0.003, 0.003, and 0.004, respectively). There were no significant associations of SNPs and possible haplotypes of MTNR1B with susceptibility to GD. CONCLUSIONS: Genetic variants of rs2119882 of MTNR1A and the AT haplotype of the combination of rs2119882 and rs13140012 were associated with GD susceptibility in an ethnic Chinese population. The results support the involvement of the melatonin pathway in the pathogenesis of GD.