Functional and structural effects of amyloid-β aggregate on Xenopus laevis oocytes

Enriched cell-free and cell-based native membrane derived vesicles (nMV) enabling rapid in-vitro electrophysiological analysis of the voltage-gated sodium channel 1.5

Here, we demonstrate the utility of native membrane derived vesicles (nMVs) as tools for expeditious electrophysiological analysis of membrane proteins. We used a cell-free (CF) and a cell-based (CB) approach for preparing protein-enriched nMVs. We utilized the Chinese Hamster Ovary (CHO) lysate-based cell-free protein synthesis (CFPS) system to enrich ER-derived microsomes in the lysate with the primary human cardiac voltage-gated sodium channel 1.5 (hNa_V1.5; SCN5A) in 3 h. Subsequently, CB-nMVs were isolated from fractions of nitrogen-cavitated CHO cells overexpressing the hNa_V1.5. In an integrative approach, nMVs were micro-transplanted into Xenopus laevis oocytes. CB-nMVs expressed native lidocaine-sensitive hNa_V1.5 currents within 24 h; CF-nMVs did not elicit any response. Both the CB- and CF-nMV preparations evoked single-channel activity on the planar lipid bilayer while retaining sensitivity to lidocaine application. Our findings suggest a high usability of the quick-synthesis CF-nMVs and maintenance-free CB-nMVs as ready-to-use tools for in-vitro analysis of electrogenic membrane proteins and large, voltage-gated ion channels.

Using Xenopus oocytes in neurological disease drug discovery

Introduction: Neurological diseases present a difficult challenge in drug discovery. Many of the current treatments have limited efficiency or result in a variety of debilitating side effects. The search of new therapies is of a paramount importance, since the number of patients that require a better treatment is growing rapidly. As an in vitro model, Xenopus oocytes provide the drug developer with many distinct advantages, including size, durability, and efficiency in exogenous protein expression. However, there is an increasing need to refine the recent breakthroughs.Areas covered: This review covers the usage and recent advancements of Xenopus oocytes for drug discovery in neurological diseases from expression and functional measurement techniques to current applications in Alzheimer's disease, painful neuropathies, and amyotrophic lateral sclerosis (ALS). The existing limitations of Xenopus oocytes in drug discovery are also discussed.Expert opinion: With the rise of aging population and neurological disorders, Xenopus oocytes, will continue to play an important role in understanding the mechanism of the disease, identification and validation of novel molecular targets, and drug screening, providing high-quality data despite the technical limitations. With further advances in oocytes-related techniques toward an accurate modeling of the disease, the diagnostics and treatment of neuropathologies will be becoming increasing personalized.

Amyloid-like substance in mice and human oocytes and embryos

PURPOSE

To identify and characterize amyloid-like substance (ALS) in human and mouse oocytes and preimplantation embryos.

METHODS

An experimental prospective pilot study. A total of 252 mouse oocytes and preimplantation embryos and 50 immature and in vitro matured human oocytes and parthenogenetic human embryos, from 11 consenting fertility patients, ages 18-45. Fluorescence intensity from immunofluorescent staining and data from confocal microscopy were quantified. Data were compared by one-way analysis of variance, with the least square-MEANS post-test, Pearson correlation coefficients (r), and bivariate analyses (t tests). ALS morphology was verified using transmission electron microscopy.

RESULTS

Immunostaining for ALS appears throughout the zona pellucida, as well as in the cytoplasm and nucleus of mouse and human oocytes, polar bodies, and parthenogenetic embryos, and mouse preimplantation embryos. In mouse, 2-cell embryos exhibited the highest level of ALS (69000187.4 ± 6733098.07). Electron microscopy confirmed the presence of ALS. In humans, fresh germinal vesicle stage oocytes exhibited the highest level of ALS (4164.74088 ± 1573.46) followed by metaphase I and II stages (p = 0.008). There was a significant negative association between levels of ALS and patient body mass index, number of days of ovarian stimulation, dose of gonadotropin used, time between retrieval and fixation, and time after the hCG trigger. Significantly higher levels of ALS were found in patients with AMH between 1 and 3 ng/ml compared to < 1 ng/ml.

CONCLUSION

We demonstrate for the first time the presence, distribution, and change in ALS throughout some stages of mouse and human oocyte maturation and embryonic development. We also determine associations between ALS in human oocytes with clinical characteristics.

Amyloid pore-channel hypothesis: effect of ethanol on aggregation state using frog oocytes for an Alzheimer's disease study

Alzheimer's disease severely compromises cognitive function. One of the mechanisms to explain the pathology of Alzheimer’s disease has been the hypotheses of amyloid-pore/channel formation by complex Aβ-aggregates. Clinical studies suggested the moderate alcohol consumption can reduces probability developing neurodegenerative pathologies. A recent report explored the ability of ethanol to disrupt the generation of complex Aβ in vitro and reduce the toxicity in two cell lines. Molecular dynamics simulations were applied to understand how ethanol blocks the aggregation of amyloid. On the other hand, the in silico modeling showed ethanol effect over the dynamics assembling for complex Aβ-aggregates mediated by break the hydrosaline bridges between Asp 23 and Lys 28, was are key element for amyloid dimerization. The amyloid pore/channel hypothesis has been explored only in neuronal models, however recently experiments suggested the frog oocytes such an excellent model to explore the mechanism of the amyloid pore/channel hypothesis. So, the used of frog oocytes to explored the mechanism of amyloid aggregates is new, mainly for amyloid/pore hypothesis. Therefore, this experimental model is a powerful tool to explore the mechanism implicates in the Alzheimer’s disease pathology and also suggests a model to prevent the Alzheimer’s disease pathology. [BMB Reports 2015; 48(1): 13-18]