Protein and Peptide Letters - Volume 25, Issue 4, 2018

Introduction: Laser Therapy (LT) has been employed for the treatment of Oral Mucositis (OM) due to its anti-inflammatory, analgesic and bio-stimulatory effects. Objective: This pilot study investigated the effect of LT on the expression of DEFB1, DEFB4, DEFB103 genes encoding for the human β-defensins 1, 2 and 3. Materials and Method: TR146 epithelial cell line, used to mimic oral mucosa, was irradiated with different LT protocols. β-defensins gene expression was evaluated using TaqMan probes on Real- Time PCR platform. Results and Conclusion: In this cellular model LT decreased mRNA defensins' expression 30 minutes after irradiation but not 24 hours later, suggesting that LT is able to influence β -defensins production immediately after treatment, while its efficacy decreases over time.

Background: Human serum albumin acts as a carrier protein to a variety of drugs and aids their transport. Andrographis paniculata, a herbal plant has been used as a source of traditional medicine in the Asian countries. Among the various constituents of this plant, andrographolide is the most active and is being used from centuries in the treatment of many chronic and infectious diseases. Objective: The present study was designed to evaluate the interaction and binding affinity of andrographolide with HSA, by molecular docking, chromatographic and spectral studies. Methods: Andrographolide was docked with crystal structure of human serum albumin (1AO6) using Auto Dock Vina software and the interactions were analyzed by a visualizing software py- MOL. For further characterization and confirmation, andrographolide (3x10-5 M) and HSA (0.001, 0.005, 0.01, 0.02, 0.04 M) sample mixtures were incubated at 37°C for 3h in a metabolic shaker, followed by centrifugation. The supernatant and the filtrate were analyzed by UV spectroscopy, HPLC, CD and FTIR spectral analysis. Results: The docking studies revealed that andrographolide interacted with HSA and formed hydrogen bonds with Trp 214, Arg 218 and Lys 444 amino acid residues. The UV spectral analysis revealed a decrease in the absorption peak of HSA due to its interaction with andrographolide. A new peak was observed at retention time 7.45 min by HPLC analysis and the Bmax was found to be 7.5 ± 0.4 mg protein with a Kd value of 1.89 mM, indicating interaction of andrographolide with HSA. The CD spectra results suggested, a marginal decrease in the negative ellipticity without any significant shift in peak, indicating the stabilization of the HSA-andrographolide complex. The FTIR analysis of the andrographolide-HSA mixture showed a peak at wave number 1637 cm−1 (a shift of amide I groups from 1646 cm−1) and 1016 cm−1 which corresponded to the ligand, confirming the complex formation. Conclusion: The molecular docking studies demonstrated the interactions of andrographolide to the crystal structure of HSA. The chromatographic and spectroscopic analysis confirmed the binding of andrographolide with HSA and their complex formation. Overall the present studies conclude the binding of andrographolide to HSA protein, favoring its pharmacokinetics.

Introduction: Interaction of surfactants with proteins can decipher important information regarding the stability and behavior of proteins. For multi-domain proteins, these interactions vary domain wise and these details are crucial in understanding the contribution of different domains of the protein in its overall activity. Objective: The objective of the present work is to study the interaction of surfactants with domain III of Human Serum Albumin (HSA) and to compare the same with the global interaction. Methods: Interaction of the anionic Sodium Dodecyl Sulphate (SDS) and the Cationic Cetyltrimethylammonium Bromide (CTAB) surfactants with domain III of Human Serum Albumin (HSA) has been studied using 8-Anilino-1-Naphthalene-Sulphonate (ANS) as a fluorescent marker. Circular Dichroism (CD) spectroscopy has been used to study the protein-surfactant interaction for the overall protein. Results: SDS is found to interact sequentially with domain III of HSA having two detectable intermediate states in the binding process. In case of CTAB, we have observed only one intermediate state for its interaction with domain III. Although Quantum yield measurement can reflect the presence of such intermediate state, the overall conformational change of the HSA on addition of surfactants, studied by Circular Dichroism (CD) spectroscopy, and the ANS-Trp distance measurement by FRET could not resolve the presence of such intermediate states. The esterase activity of HSA in presence of different amount of surfactants is also in accordance with our above observation. Conclusion: The interaction of both the surfactants with HSA is found to be sequential in nature. The most important conclusion revealed from our study is that the nature of protein-surfactant interaction is not same throughout the entire protein. Our study reveals that different parts of the multi-domain HSA have different affinity to the surfactant molecules.

Background: SjOgren's Syndrome (SS) is a systemic and chronic autoimmune disorder that affects the exocrine glands with massive autoantibody production. Although the pathogenesis of the disorder is incompletely understood, but some studies have reported that anti-moesin antibodies have been detected in autoimmune diseases with which SS is closely associated. Here, we have investigated moesin's potential involvement in SS. Objective: This study aims to verify whether moesin is a specific autoantigen involved in Chinese Hans SS patients. Methods: First, recombinant human moesin was expressed and purified. Next, the protein was verified as antigen by Western blotting and immunoprecipitation. The positive protein band in the immunoprecipitation was identified by (MALDI-TOF/TOF). Finally, an optimized ELISA (Enzyme- Linked Immunosorbent Assay) kit was developed to measure the titer concentration of anti-moesin antibody-positive patients in a large cohort of clinical subjects. Results: Univariate analysis revealed that the proportion of individuals positive for serum IgG against recombinant human moesin was 42 % in a group of Chinese Hans SS patients (21 of 50), 22 % in systemic lupus erythematosus patients and (11 of 50), compared to only 4 % in healthy controls (2 of 50). Conclusion: An association between anti-moesin antibodies and SS manifestation have been found which may be considered a suspected serum biomarker for the development of SS.

Background: Type 2 Diabetes (T2D) is a metabolic disease which affects glucose homeostasis caused due to inability of the target cells to respond to insulin. Role of vitamin D in the pathogenesis and prevention of T2D has sparked widespread interest. Vitamin D plays a classical role in Ca++ homeostasis as well as regulates insulin secretion from β-cells and its action on various target cells. Proteins are the vital components of all cellular processes and their expression alters in response to various external or internal stimuli. Alteration in protein structure, function may contribute to the pathogenesis of many diseases including diabetes. Protein expression during the exposure of the cells to different glucose concentrations may alter and can give vital information about the pathogenesis of T2D. Objective: To study the effect of different glucose concentrations and supplementation of vitamin D on proteomic profile of L6 cell lines. Method: L6 skeletal muscle cells were exposed to different Glucose (G) concentrations (0mM, 8mM, 16mM and 25mM) supplemented with Vitamin D (VD) for 48 hours. Total cell protein was extracted and protein profile was studied using SDS-PAGE. Three distinct bands observed in SDSPAGE in samples obtained from cells which were exposed to 8mM (G), 8mM (G) + VD and 16mM (G). The distinct bands were excised, in gel digestion were performed and MALDI-TOF analysis of the samples were done. Results: MALDI-TOF analysis revealed these bands as mitochondrial uncoupling protein 3 (UCP3 MOUSE), Insulin gene enhancer protein 2 (ISL2 MOUSE) and Tubulin polyglutamylase complex1 (TPGS1 MOUSE) respectively. UCP3 protein is primarily expressed in the skeletal muscle cells and is involved in energy homeostasis and modulates insulin sensitivity. ISL2 protein plays an important role in differentiation and maintenance of the tissues. TPGS1 helps in microtubule polymerization might be helping in glucose transport and also play crucial role in the cellular movement, organization of intracellular structure, and intracellular transport. Conclusion: These identified proteins may provide information about disease pathophysiology and can serve as potential targets for therapeutic intervention of T2D. Further studies on the changes of protein expression under high glucose concentration and supplementation with vitamin D will lead to better understanding of the molecular mechanisms of T2D.

Background: Protein-carbohydrate interactions play vital roles in several biological processes in living organisms. The comparative analysis of binding site residues along with stabilizing residues in protein-carbohydrate complexes provides ample insights to understand the structure, function and recognition mechanism. Objective: The main objective of this study is to identify and analyze the residues, which are involved in both folding and binding of the protein-carbohydrate complexes. Methods: We have identified the stabilizing residues using the knowledge of hydrophobicity, longrange interactions and conservation, as well as binding site residues using a distance cutoff of 3.5Å between any heavy atoms in protein and ligand. Residues, which are common in stabilizing and binding, are termed as key residues. These key resides are analyzed with various sequence and structure based parameters such as frequency of occurrence, surrounding hydrophobicity, longrange order and conservation score. Results: In this work, we have identified 2.45% binding site residues in a non-redundant dataset of 1130 complexes using distance-based criteria and 7.07% stabilizing residues using the concepts of hydrophobicity, long-range interactions and conservation of residues. Further, 5.9% of binding and 2.04% of stabilizing residues are common to each other, which are termed as key residues. The key residues have been analysed based on protein classes, carbohydrate types, gene ontology functional classifications, amino acid preference and structure-based parameters. We found that all-β, α+β and α/β have more key residues than other protein classes and most of the KRs are present in β-strands, which shows their importance in stability and binding of complexes. On the ligand side, Lsaccharide has the highest number of key residues and it has a high percentage of KRs in SRs and BRs than other carbohydrate types. Further, polar and charged residues have a high tendency to serve as key residues. Classifications based on gene ontology terms revealed that Lys is preferred in all the three groups: molecular functions, biological processes and cellular components. Key residues have 6 to 9 contacts within the protein and make only one contact with the carbohydrate ligand. These contacts are dominant to form polar-nonpolar contacts followed by the contacts between charged atoms. Further, the influence of sequence and structural parameters such as surrounding hydrophobicity, solvent accessibility, secondary structure, long-range order and conservation score has been discussed. Conclusion: The results obtained in the present work provide deep insights for understanding the interplay between stability and binding in protein-carbohydrate complexes.

Background: The 5HT2A G-Protein Coupled Receptor (GPCR) is an important family of receptors involved in an array of neuromodulatory functions. Their dysregulation has been implicated in a number of psychiatric diseases. In spite of the importance of this GPCR, high resolution structure and mechanistic details of its function is unknown. Cholesterol plays an important role in the function of many receptors and reduced cholesterol levels can lead to disruption of serotonergic pathways. However, the role of cholesterol in the formation of GPCR oligomers has not been previously shown for this receptor. Given that receptor dimers have been shown to be the functional unit of this receptor, it is important to investigate the effect of cholesterol in the oligomeric state of 5HT2A receptor. Objectives: The main objective of this work is to clone, over-express and purify the 5HT2A receptor and investigate the effect of cholesterol in its oligomer formation. Methods: The 5HT2A receptor (5HT2AR) DNA construct was subcloned into pFastBac-HT vector and the purified bacmid was used to transfect healthy Sf9 cells. After subsequent passages, a high titer baculovirus was used for over-expression in Sf9 cells. To verify whether the over-expressed receptor was localized in the membrane or cytosolic fraction, cells with and without baculoviral infection were analyzed by immunocytochemistry. Subsequently, the over-expression conditions required to obtain sufficient quantity of the receptor was optimized followed by the optimization of the purification conditions. Finally, the culture was scaled up and the receptor was purified by affinity chromatography. The over-expression of the receptor was checked by Western blotting and purity was analyzed by Coomassie stained SDS PAGE. Cryo-electron microscopy experiments were performed on the purified receptor in presence and absence of cholesterol and at multiple concentrations to rule out any concentration dependent effect on the oligomer formation. Results: Immunocytochemistry experiments showed prominent nuclear staining; however, bright green staining along the cell membrane was observed only for the infected cells, suggesting appropriate trafficking of majority of the over-expressed receptors to the cell membrane. Results of cryoelectron microscopy show that the receptor with cholesterol had particles that were bigger in size (~11 – 12 nm) compared to the dimension of known GPCR homologs. In contrast, the receptor after removal of cholesterol revealed a uniform distribution of smaller particles (~5 – 6 nm) that is approximately half the size of 5HT2AR particles with cholesterol. Comparing the 2D average views of detergent-encapsulated 5HT2AR particles with the overall dimensions of other 5HT receptor analogs, we show that while a 5HT2AR dimer more closely matches the dimensions of particles with CHS, only a monomer can be fit to particles without CHS. Importantly, even at higher receptor concentration and particle density, the size for 5HT2AR particles without CHS remains the same, suggesting that dimerization is unlikely an effect of concentration. Conclusion: Our results indicated that 5HT2A receptor primarily forms a dimer in presence of cholesterol whereas it predominantly forms a monomer when cholesterol is removed.

Background: The role of intracellular proteins in the pathogenesis of absence epilepsy were mentioned. These proteins are thought to be related to energy generation, signal transduction, inflammation processes and membrane conductance. Objectives: The investigation of protein profile of the genetically epileptic rat brains was the main subject of this study. Methods: For this, a 2D-gel electrophoresis based comparative proteome analysis was performed using thalamus tissue of genetic absence epileptic WAG/Rij and age matched Wistar rats. Regulated spots displaying differences in their abundance were identified using MALDI-TOF/TOF. Among the six spots (DHRS9, BR44, HINT1, CREM, SPRE and PDIA3/ERp57) the highest mascot score was attributed to ERp57 a neuroprotective/neurodegenerative system associated protein. Western Blot analyses were performed to validate changes occurring at ERp57 in thalamus and also identify changes in fronto-parietal cortex. Results: Reductions in the expression levels of ERp57 were detected in the thalamic and the fronto-parietal brain regions of the WAG/Rij rats in comparison to Wistar rats. Conclusion: Such difference might be associated with the pathogenic mechanisms dictating the absence epilepsy. Lower levels of ERp57 may be playing an important role in the development of spontaneous seizures activity seen in the absence epileptic WAG/Rij rats strain.