Molecular Mechanism of Beta-Arrestin-dependent ERK activation Downstream of Protease-activated Receptor-2

β-arrestins, originally discovered in the context of G protein-coupled receptor (GPCR) desensitization and internalization, also function in signaling of these receptors independently of G protein coupling. These novel functions involve the roles for β-arrestins as scaffolds. It has been reported that β-arrestins interact with a number of binding partners including trafficking proteins, cytosolic kinases, cytoskeletal proteins, and non-receptor tyrosine kinase. Downstream of protease-activated receptor-2 (PAR-2), β-arrestin scaffolds the components of the ERK cascade, Raf-1, MEK1, and ERK1/2 with the receptor at the plasma membrane, leading to activation of cytoplasmic/membrane ERK1/2 signaling independent of G-protein coupling. Furthermore, we previously demonstrated that stimulation of PAR-2 resulted in prolonged activation of ERK1/2 in pseudopodia in a β-arrestin-dependent manner and β-arrestins were required in PAR-2 mediated ERK1/2 activation at the membrane and cell migration in metastatic tumor cell lines, suggesting β-arrestin-dependent ERK1/2 activation might play a role in cell motility. Although a number of recent studies reported that β-arrestins are required for ERK1/2 activation independently of G protein coupling, molecular mechanism of β-arrestin- mediated ERK1/2 activation via c-Raf has remained unclear. We hypothesized that the ability of β-arrestins to scaffold and prolong MAPK signaling at the membrane, is dependent upon precise molecular interactions that are facilitated by interaction of β-arrestins with PAR-2. To investigate the hypothesis, we determined the sites/domains in β-arrestin-1 that interact with components of the ERK module (c-Raf, MEK1, and ERK1/2) both in vitro and in cells using GST pull down assay, sandwich immunoassay, and co-immunoprecipitation and investigated the role of these identified regions of β-arrestin for interaction and activation of ERK1/2 using truncated mutants of β-arrestin or β-arrestin mutants lacking domains. In addition, a mysterious link in functional mechanism of β-arrestin-mediated ERK1/2 activation is how c-Raf relieves autoinhibition engendering a conformation change from a closed, inactive state to an open, active state, without small GTPase Ras, which is critical for c-Raf activation in the classical G protein dependent ERK activation. We hypothesized that β-arrestins behave similar to Ras for β-arrestin-dependent ERK activation to relieve autoinhibition of c-Raf. We have proved that β-arrestin-1 binds to the regulatory domain of c-Raf where Ras was indentified to bind. Therefore, binding of β-arrestin-1 to c-Raf might ensure formation of scaffolding complex containing β-arrestin-1 and the ERK cascade and play a critical role to activate c-Raf in β-arrestin-dependent ERK1/2 activation

Clinical evaluation of noninvasive prenatal testing for sex chromosome aneuploidies in 9,176 Korean pregnant women: a single-center retrospective study

Abstract Background To evaluate the clinical significance of noninvasive prenatal testing (NIPT) for detecting fetal sex chromosome aneuploidies (SCAs) in Korean pregnant women. Methods We retrospectively analyzed NIPT data from 9,176 women with singleton pregnancies referred to the CHA Biotech genome diagnostics center. Cell-free fetal DNA (cffDNA) was extracted from maternal peripheral blood, and high-throughput massively parallel sequencing was conducted. Subsequently, the positive NIPT results for SCA were validated via karyotype and chromosomal microarray analyses. Results Overall, 46 cases were SCA positive after NIPT, including 20, 12, 8, and 6 for Turner, triple X, Klinefelter, and Jacob syndromes, respectively. Among 37 women with invasive prenatal diagnosis, 19 had true positive NIPT results. The overall positive predictive value (PPV) of NIPT for detecting SCAs was 51.35%. The PPV was 18.75% for Turner, 88.89% for triple X, 71.43% for Klinefelter, and 60.00% for Jacob’s syndromes. NIPT accuracy for detecting sex chromosome trisomies was higher than that for sex chromosome monosomy (P = 0.002). No significant correlation was observed between fetal SCA incidence and maternal age (P = 0.914), except for the borderline significance of Jacob’s syndrome (P = 0.048). No significant differences were observed when comparing NIPT and karyotyping validation for fetal SCA according to pregnancy characteristics. Conclusion Our data suggest that NIPT can reliably screen for SCAs, and it performed better in predicting sex chromosome trisomies compared with monosomy X. No correlation was observed between maternal age and fetal SCA incidence, and no association was observed between different pregnancy characteristics. The accuracy of these findings requires improvements; however, our study provides an important reference for clinical genetic counseling and further management. Larger scale studies, considering confounding factors, are required for accurate evaluation

Germanium Silicon Alloy Anode Material Capable of Tunable Overpotential by Nanoscale Si Segregation

We developed the novel electrode that enables fine control of overpotential by exploiting surface segregation that is the enrichment of one component at the surface of binary alloy. To realize this approach, we controlled the proportion of Si with low Li diffusivity at the surface by annealing the SiGe nanowire in H-2 environment at various temperatures. The resulting SiGe nanowires annealed at 850 degrees C exhibited high reversible capacity (>1031 mA.h.g(-1)), and long cycle life (400 cycles) with high opacity retention (89.0%) at 0.2 C. This superior battery performance is attributed to the remaining unlithiated part acting as support frame to prevent pulverization of anode material, which results from the fine-tuning of overpotential by controlling the degree of Si segregation.close0