Electrochemical Investigations of Tau Protein Phosphorylations and Interactions with Pin1

Restoration of miR-328a-5p function curtails hypoxic pulmonary hypertension through a mechanism involving PIN1/GSK3β/β-catenin axis

Recent evidence has highlighted the involvement of microRNAs (miRs) in hypoxic pulmonary hypertension (PH), which can be induced under hypoxic conditions. We intend to explore whether the miR-328a-5p/PIN1 axis affects hypoxic PH by regulating the GSK3β/β-catenin signaling pathway. The GEO database was retrieved to single out key miRs affecting hypoxic PH. It was observed that downregulation of miR-328a-5p occurred in hypoxia-induced PH samples. The binding affinity between miR-328a-5p to PIN1 was predicted by a bioinformatics tool and verified using a dual luciferase reporter gene assay. Rat primary pulmonary artery smooth muscle cells (PASMCs) were exposed to hypoxia for in vitro cell experiments. miR-328a-5p could target and downregulate PIN1 expression, leading to suppressed GSK3β/β-catenin activation. In addition, GSK3β/β-catenin inactivation curtailed hypoxia-induced vascular inflammatory responses and proliferation and migration in PASMCs in vitro. A hypoxic PH model was established in SD rats to observe the effects of miR-328a-5p on hemodynamic parameters and right heart remodeling. It was demonstrated in vivo that miR-328a-5p downregulated PIN1 expression to suppress GSK3β/β-catenin signaling, thereby reducing the vascular inflammatory response and alleviating disease progression in hypoxia-induced PH rats. The evidence provided by our study highlighted the involvement of miR-328a-5p in the translational suppression of PIN1 and the blockade of the GSK3β/β-catenin signaling pathway, resulting in attenuation of hypoxic PH progression.

Electrochemical distinction of neuronal and neuroblastoma cells via the phosphorylation of the cellular extracellular membrane

In this contribution we establish a proof of concept method for monitoring, quantifying and differentiating the extracellular phosphorylation of Human SHSY5Y undifferentiated neuronal cells and neuroblastoma cells by three prominent ectokinases PKA, PKC and Src. Herein it is demonstrated that a combination of different experimental techniques, including fluroesence microscopy, quartz crystal microscopy (QCM) and electrochemistry, can be used to detect extracellular phosphorylation levels of neuronal and neuroblastoma cells. Phosphorylation profiles of the three ectokinases, PKA, PKC and Src, were investigated using fluorescence microscopy and the number of phosphorylation sites per kinase was estimated using QCM. Finally, the phosphorylation of the extracellular membrane was determined using electrochemistry. Our results clearly demonstrate that the extracellular phosphorylation of neuronal cells differs significantly in terms of its phosphorylation profile from diseased neuroblastoma cells and the strength of surface electrochemical techniques in the differentiation process. We reveal that using electrochemistry, the percent compositions of neuronal and neuroblastoma cells can also be identified.

Electrochemical detection of neuronal extracellular phosphorylation by PKA, PKC and Src

The focus of this work described here is to establish a method for monitoring and quantifying the extracellular phosphorylation of Human SHSY5Y undifferentiated neuronal cells by three ectokinases PKA, PKC and Src; these are kinases that are known to be present in the extracellular matrix. Here is demonstrated that a combination of different experimental techniques, including microscopy and electrochemistry, can be used to detect extracellular phosphorylations. Phosphorylation profiles of the three ectokinases, PKA, PKC and Src, were investigated using fluorescence microscopy and the number of phosphorylation sites per kinase was estimated using QCM. Finally, the phosphorylation of the extracellular membrane was determined using electrochemistry. Our results clearly demonstrate the extracellular phosphorylation of neuronal cells and the strength of surface electrochemical techniques in the investigation of cellular phosphorylation.

Accurate Identification of Human Phosphorylated Proteins by Ensembling Supervised Kernel Self-organizing Maps

Protein phosphorylation is a vital physiological process, which plays a critical role in controlling survival differentiation, cell growth, metabolism and apoptosis. The accurate identification of whether a protein will be phosphorylated solely from protein sequence is especially useful for both basic research and drug development. In this study, a new predictor specifically designed for the prediction of human phosphorylated proteins is proposed. The proposed method first train two supervised kernel self-organizing maps (SKSOMs): one is trained with feature from protein physiochemical composition view, while the other is trained with feature from protein evolutionary information view. Then, the two trained SKSOMs are ensembled to perform the final prediction. Rigorous computational experiments show that the proposed method achieves 78.75 % and 0.561 on ACC and MCC, which are 6.96 % and 12.5 % higher than that of the state-of-the-art predictor. Overall, the study demonstrated a new sensitive avenue to identify human phosphorylated proteins and could be readily extended to recognize phosphorylated proteins for other species.

Nano-biosensors to detect beta-amyloid for Alzheimer's disease management

Beta-amyloid (β-A) peptides are potential biomarkers to monitor Alzheimer's diseases (AD) for diagnostic purposes. Increased β-A level is neurotoxic and induces oxidative stress in brain resulting in neurodegeneration and causes dementia. As of now, no sensitive and inexpensive method is available for β-A detection under physiological and pathological conditions. Although, available methods such as neuroimaging, enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) detect β-A, but they are not yet extended at point-of-care (POC) due to sophisticated equipments, need of high expertize, complicated operations, and challenge of low detection limit. Recently, β-A antibody based electrochemical immuno-sensing approach has been explored to detect β-A at pM levels within 30-40 min compared to 6-8h of ELISA test. The introduction of nano-enabling electrochemical sensing technology could enable rapid detection of β-A at POC and may facilitate fast personalized health care delivery. This review explores recent advancements in nano-enabling electrochemical β-A sensing technologies towards POC application to AD management. These analytical tools can serve as an analytical tool for AD management program to obtain bio-informatics needed to optimize therapeutics for neurodegenerative diseases diagnosis management.

A multifunctional ELISA to measure proteins: oxPin1 in Alzheimer's brain as an example

Background

Oxidative stress occurs in many neurodegenerative diseases including Alzheimer's disease (AD) and evidence suggests that specific proteins are oxidised in individual diseases. Thus measures of oxidised proteins such as in human biological samples could represent potential disease-specific biomarkers. Protein carbonylation is considered to be an important marker of oxidative stress. In AD in particular, the peptidyl prolyl isomerase, Pin1, has been shown to be sensitive to metal-catalysed oxidation with the addition of carbonyl side-chains.

Methods

Based on this protein modification we developed a novel, enzyme-linked sandwich immunoassay for the quantification of oxidised Pin1 (oxPin1) in human brain tissue samples.

Results

We successfully developed an ELISA for the measurement of oxidised Pin1 in biological samples and measured oxPin1 in hippocampal tissue extracts from controls and AD, which showed an increased ratio of oxPin1 to total Pin1 in patients with early AD pathology compared with controls.

Conclusions

We show that oxidised proteins, in this case oxPin1, can be measured using the developed ELISA. In addition, our results support the presence of increased oxidative stress in the early stages of AD pathology and show that the oxPin1/Pin1 ratio could indicate early stage pathology. This warrants further investigation in other biological fluids.

General significance

Importantly, further development and adaption of the assay design will enable multi-functional use for the quantification of oxidised proteins in tissues and biological fluids that may be used in investigating the role of oxidised proteins in a range of neurodegenerative diseases, particularly in which disease-specific protein oxidation has been implicated.

Protein phosphorylation detection using dual-mode field-effect devices and nanoplasmonic sensors

Phosphorylation by kinases is an important post-translational modification of proteins. It is a critical control for the regulation of vital cellular activities, and its dysregulation is implicated in several diseases. A common drug discovery approach involves, therefore, time-consuming screenings of large libraries of candidate compounds to identify novel inhibitors of protein kinases. In this work, we propose a novel method that combines localized surface plasmon resonance (LSPR) and electrolyte insulator semiconductor (EIS)-based proton detection for the rapid identification of novel protein kinase inhibitors. In particular, the selective detection of thiophosphorylated proteins by LSPR is achieved by changing their resonance properties via a pre-binding with gold nanoparticles. In parallel, the EIS field-effect structure allows the real-time electrochemical monitoring of the protein phosphorylation by detecting the release of protons associated with the kinases activity. This innovative combination of both field-effect and nanoplasmonic sensing makes the detection of protein phosphorylation more reliable and effective. As a result, the screening of protein kinase inhibitors becomes more rapid, sensitive, robust and cost-effective.

Protein phosphorylation analysis based on proton release detection: potential tools for drug discovery

Phosphorylation is the most important post-translational modification of proteins in eukaryotic cells and it is catalysed by enzymes called kinases. The balance between protein phosphorylation and dephosphorylation is critical for the regulation of physiological processes and its unbalance is the cause of several diseases. Conventional assays used to analyse the kinase activity are limited as they rely heavily on phospho-specific antibodies and radioactive tags. This makes their use impractical for high throughput drug discovery platforms. We have developed two versatile methods to detect the release of protons (H(+)) associated with the protein phosphorylation catalysed by kinases. The first approach is based on the pH-sensitive response of oxide-semiconductor interfaces and the second method detects the pH changes in phosphorylation reaction using a commercial micro-pH electrode. The proposed methods successfully detected phosphorylation of myelin basic protein by PKC-α kinase. These techniques can be readily adopted for multiplexed arrays and high throughput analysis of kinase activity, which will represent an important innovation in biomedical research and drug discovery.