The product of the gene GEF1 of Saccharomyces cerevisiae transports Cl- across the plasma membrane
FEMS YEAST RESEARCH
Authors: Lopez-Rodriguez, Angelica; Carabez Trejo, Alfonso; Coyne, Leanne; Halliwell, Robert F.; Miledi, Ricardo; Martinez-Torres, Ataulfo
Abstract
Expression of GEF1 in Xenopus laevis oocytes and HEK-293 cells gave rise to a Cl- channel that remained permanently open and was blocked by nitro-2-(3-phenylpropylamino) benzoic acid and niflumic acid. NPPB induced petite-like colonies, resembling the GEF1 knock-out. The fluorescent halide indicator SPQ was quenched in a wild-type strain, in contrast to both a GEF1 knock-out strain and yeast grown in the presence of NPPB. Immunogold and electron microscopy located Gef1p in the plasma membrane, vacuole, endoplasmic reticulum and Golgi apparatus. Eleven substitutions in five residues forming the ion channel of GEF1 were introduced; some of them (S186A, I188N, Y459D, Y459F, Y459V, I467A, I467N and F468N) did not rescue the pet phenotype, whereas F468A, A558F and A558Y formed normal colonies. All the pet mutants showed reduced O-2 consumption, small mitochondria and mostly disrupted organelles. Finally, electron microscopy revealed that the plasma membrane of the mutants develop multiple foldings and highly ordered cylindrical protein-membrane complexes. All the experiments above suggest that Gef1p transports Cl- through the plasma membrane and reveal the importance of critical amino acids for the proper function of the protein as suggested by structural models. However, the mechanism of activation of the channel has yet to be defined.
Evidence of an Association between Age-Related Functional Modifications and Pathophysiological Changes in Zebrafish Heart
GERONTOLOGY
Authors: Sun, Yanyi; Fang, Yuehua; Xu, Xiaolei; Lu, Guoping; Chen, Zhenyue
Abstract
Background: Zebrafish have become a valuable model for the study of developmental biology and human disease, such as cardiovascular disease. It is difficult to discriminate between disease-related and age-related alterations. Objective: This study was aimed to investigate the effects and potential mechanisms of age-related cardiac modifications in an older zebrafish population. Methods: In this study, we calculated the survival rate and measured the spinal curvature through the aging process. A swimming challenge test was performed and showed that swimming capacity and endurance dramatically dropped in older fish groups. Results: To find out the effect of stress on zebrafish during the aging process, we recorded electrocardiograms on zebrafish and showed that during stress, aging not only led to a significant reduction in heart rate, but also caused other age-related impairments, such as arrhythmias and ST-T depression. Echocardiography showed a marked increase in end-diastolic ventricular dimensions and in isovolumic relaxation time and a notably slower mean and peak velocity of the bulboventricular valve in older zebrafish, but stroke volume and cardiac output were not different in young and old zebrafish. Both nppa and nppb (cardiac fetal genes for natriuretic factor) expression detected by real-time polymerase chain reaction analysis increased in older fish compared to the younger group. Histological staining revealed fibrosis within cardiomyocytes and an increase in ventricular myocardial density and a decrease in epicardial vessel dimensions in older fish hearts that may correlate with a deterioration of cardiac function and exercise capacity. Conclusion: These data suggest that cardiac functional modifications in zebrafish are comparable to those in humans and may partly be due to changes in the cardiovascular system including cardiac fetal gene reprogramming, myocardial density, and epicardial vessel dimensions. (C) 2014 S. Karger AG, Basel