thangasamy74 Thangasamy
  • West Virginia State University
Research fields
  • Molecular biology
Differential Analysis of N-glycopeptide Abundance and N-glycosylation Site Occupancy for Studying Protein N-glycosylation Dysregulation in Human Disease
Authors:  Qi Zhang, Cheng Ma, Lian Li and Lih-Shen Chin, date: 06/20/2021, view: 2735, Q&A: 0

Protein N-glycosylation plays a vital role in diverse cellular processes, and dysregulated N-glycosylation is implicated in a variety of human diseases including neurodegenerative disorders and cancer. With recent advances in high-resolution mass spectrometry-based glycoproteomics technologies enabling large-scale N-glycoproteome profiling of disease and control samples, analysis of the large datasets has become a challenge. Here, we provide a protocol for the systems-level analysis of in vivo N-glycosylation sites on N-glycosylated proteins and their changes in human disease, such as Alzheimer's disease. The protocol includes quantitation and differential analysis of N-glycopeptide abundance, in addition to integrative N-glycoproteome and proteome data analyses, to determine disease-associated changes in N-glycosylation site occupancy and identify differentially N-glycosylated proteins in human disease versus control samples. This protocol can be modified and applied to study proteome-wide N-glycosylation alterations in response to different cellular stresses or pathophysiological states in other organisms or model systems.

Preparation of Single Epithelial Cells Suspension from Mouse Mammary Glands
Authors:  Heng Sun, Xiaoling Xu and Chuxia Deng, date: 02/20/2020, view: 4528, Q&A: 0
Single cell RNA sequencing is a very powerful means for cellular heterogeneous studies and so becoming wildly utilized nowadays. To guarantee the success of such analysis, it is very important, though sometimes difficult, to obtain single cells suspension with high quality, especially from the primary solid organs like mammary glands. Digestion of mouse or human mammary glands with enzymes was previously described. However, the yield, viability, especially the separation degree of the cells have rarely been noticed in these studies. Here we described a detailed protocol for the single epithelial cells suspension preparation from mouse mammary glands, which could be applied for single cell RNA sequencing on different platforms. This protocol could be well adapted for dissociation of other solid organs and tumors, and the single cell suspension could be also used for many other experiments.
A Yeast Chromatin-enriched Fractions Purification Approach, yChEFs, from Saccharomyces cerevisiae
We have adapted a previous procedure and improved an approach that we named yChEFs (yeast Chromatin Enriched Fractions) for purifying chromatin fractions. This methodology allows the easy, reproducible and scalable recovery of proteins associated with chromatin. By using yChEFs, we bypass subcellular fractionation requirements involved when using zymolyase to obtain the spheroplast, which is employed in many other procedures. Employing small amount of culture cells and small volumes of solutions during the yChEFs procedure is very useful to allow many samples to be handled at the same time, and also reduces costs and efforts. The purified proteins associated with chromatin fractions obtained by yChEFs can be analyzed by Western blot (Figure 1) or combined with mass spectrometry for proteomic analyses.
High Throughput Traction Force Microscopy for Multicellular Islands on Combinatorial Microarrays
Authors:  Ian C. Berg and Gregory H. Underhill, date: 11/05/2019, view: 5349, Q&A: 0
The composition and mechanical properties of the cellular microenvironment along with the resulting distribution of cellular devolved forces can affect cellular function and behavior. Traction Force Microscopy (TFM) provides a method to measure the forces applied to a surface by adherent cells. Numerous TFM systems have been described in literature. Broadly, these involve culturing cells on a flexible substrate with embedded fluorescent markers which are imaged before and after relaxion of cell forces. From these images, a displacement field is calculated, and from the displacement field, a traction field. Here we describe a TFM system using polyacrylamide substrates and a microarray spotter to fabricate arrays of multicellular islands on various combinations of extra cellular matrix (ECM) proteins or other biomolecules. A microscope with an automated stage is used to image each of the cellular islands before and after lysing cells with a detergent. These images are analyzed in a semi-automated fashion using a series of MATLAB scripts which produce the displacement and traction fields, and summary data. By combining microarrays with a semi-automated implementation of TFM analysis, this protocol enables evaluation of the impact of substrate stiffness, matrix composition, and tissue geometry on cellular mechanical behavior in high throughput.
Fluorophore-Based Mitochondrial Ca2+ Uptake Assay
Author:  Charles B. Phillips, date: 07/20/2018, view: 6456, Q&A: 0
The physiological importance of mitochondrial calcium uptake, observed in processes such as ATP production, intracellular calcium signaling, and apoptosis, makes desirable a simple, straightforward way of investigating this event with unambiguous results. The following protocol uses a calcium-sensitive, membrane-impermeable fluorophore to monitor extra-mitochondrial calcium levels in the presence of permeabilized mammalian cells harboring activated mitochondria.
γ-Secretase Epsilon-cleavage Assay
γ-Secretase epsilon-cleavage assay is derived from the cell-based Tango assay (Kang et al., 2015), and is a fast and sensitive method to determine the initial cleavage of C99 by γ-secretase. In this protocol, we use HTL cells, which are HEK293 cells with a stably integrated luciferase reporter under the control of the bacterial tetO operator element, in which C99 C terminally fused to a reversed tetracyclin-inducible activator (rTA) transcriptional activator is expressed. Endogenous or transfected γ-secretase cleaves a C terminally fused rTA transcriptional activator from C99, allowing rTA to move to the nucleus to activate a luciferase reporter gene as a measurement for γ-secretase cleavage activity.
The Long-lived Protein Degradation Assay: an Efficient Method for Quantitative Determination of the Autophagic Flux of Endogenous Proteins in Adherent Cell Lines
Authors:  Morten Luhr, Frank Sætre and Nikolai Engedal, date: 05/05/2018, view: 9598, Q&A: 0
Autophagy is a key player in the maintenance of cellular homeostasis in eukaryotes, and numerous diseases, including cancer and neurodegenerative disorders, are associated with alterations in autophagy. The interest for studying autophagy has grown intensely in the last two decades, and so has the arsenal of methods utilised to study this highly dynamic and complex process. Changes in the expression and/or localisation of autophagy-related proteins are frequently assessed by Western blot and various microscopy techniques. Such analyses may be indicative of alterations in autophagy-related processes and informative about the specific marker being investigated. However, since these proteins are part of the autophagic machinery, and not autophagic cargo, they cannot be used to draw conclusions regarding autophagic cargo flux. Here, we provide a protocol to quantitatively assess bulk autophagic flux by employing the long-lived protein degradation assay. Our procedure, which traces the degradation of 14C valine-labelled proteins, is simple and quick, allows for processing of a relatively large number of samples in parallel, and can in principle be used with any adherent cell line. Most importantly, it enables quantitative measurements of endogenous cargo flux through the autophagic pathway. As such, it is one of the gold standards for studying autophagic activity.
A General Method for Intracellular Protein Delivery through ‘E-tag’ Protein Engineering and Arginine Functionalized Gold Nanoparticles
Authors:  Rubul Mout and Vincent M. Rotello, date: 12/20/2017, view: 7247, Q&A: 0
In this protocol, we describe a method for direct cytosolic protein delivery that avoids endosomal entrapment of the delivered proteins. We achieved this by tagging the desired protein with an oligo glutamic acid tag (E-tag), and subsequently using carrier gold nanoparticles to deliver these E-tagged proteins. When E-tagged proteins and nanoparticles were mixed, they formed nanoassemblies, which got fused to cell membrane upon incubation and directly released the E-tagged protein into cell cytosol. We used this method to deliver a wide variety of proteins with different sizes, charges, and functions in various cell lines (Mout et al., 2017).

To use this protocol, the first step is to generate the required materials (gold nanoparticles, recombinant E-tagged proteins). Laboratory-synthesis of gold nanoparticles has been previously described (Yang et al., 2011). Desired E-tagged proteins can be cloned from the corresponding genes, and expressed and purified using standard laboratory procedures. We will use E-tagged green fluorescent protein (GFP) as a reference protein here. Users can simply insert an E-tag into their protein of interest, at either terminus. To achieve maximum delivery efficiency, we suggest users testing different length of E-tags. For example, we inserted E = 0 to 20 (E0 means no E-tag insertion, and E20 means 20 glutamic acids insertion in a row) to most of the proteins we tested, and screened for optimal E-tagged length for highest delivery efficiency. E10-tagged proteins gave us the highest delivery efficiency for most of the proteins (except for Cas9, where E20 tag showed highest delivery efficiency).

Once these materials are ready, it takes about ~10 min to make the E-tagged protein and nanoparticle nanoassemblies, which are immediately used for delivery. Complete delivery (~100% for GFP-E10) is achieved in less than 3 h.
Single-molecule RNA Fluorescence in situ Hybridization (smFISH) in Caenorhabditis elegans
Single-molecule RNA fluorescence in situ hybridization (smFISH) is a technique to visualize individual RNA molecules using multiple fluorescently-labeled oligonucleotide probes specific to the target RNA (Raj et al., 2008; Lee et al., 2016a). We adapted this technique to visualize RNAs in the C. elegans whole adult worm or its germline, which enabled simultaneous recording of nascent transcripts at active transcription sites and mature mRNAs in the cytoplasm (Lee et al., 2013 and 2016b). Here we describe each step of the smFISH procedure, reagents, and microscope settings optimized for C. elegans extruded gonads.
In vivo Mitophagy Monitoring in Caenorhabditis elegans to Determine Mitochondrial Homeostasis
Authors:  Konstantinos Palikaras and Nektarios Tavernarakis, date: 04/05/2017, view: 10116, Q&A: 0
Perturbation of mitochondrial function is a major hallmark of several pathological conditions and ageing, underlining the essential role of fine-tuned mitochondrial activity (Lopez-Otin et al., 2013). Mitochondrial selective autophagy, known as mitophagy, mediates the removal of dysfunctional and/or superfluous organelles, preserving cellular and organismal homeostasis (Palikaras and Tavernarakis, 2014; Pickrell and Youle, 2015; Scheibye-Knudsen et al., 2015). In this protocol, we describe a method for assessing mitophagy in the nematode Caenorhabditis elegans.
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