Molecular docking and simulation of Curcumin with Geranylgeranyl Transferase1 (GGTase1) and Farnesyl Transferase (FTase)

Protein prenylation is a posttranslational modification that is indispensable for translocation of membrane GTPases like Ras, Rho, Ras etc. Proteins of Ras family undergo farnesylation by FTase while Rho family goes through geranylgeranylation by GGTase1. There is only an infinitesimal difference in signal recognition between FTase and GGTase1. FTase inhibitors mostly end up selecting the cells with mutated Ras proteins that have acquired affinity towards GGTase1 in cancer microcosms. Therefore, it is of interest to identify GGTase1 and FTase dual inhibitors using the docking tool AutoDock Vina. Docking data show that curcumin (from turmeric) has higher binding affinity to GGTase1 than that of established peptidomimetic GGTase1 inhibitors (GGTI) such as GGTI-297, GGTI-298, CHEMBL525185. Curcumin also interacts with FTase with binding energy comparable to co-crystalized compound 2-[3-(3-ethyl-1-methyl-2-oxo-azepan-3-yl)-phenoxy]-4-[1-amino-1-(1-methyl-1h-imidizol-5-yl)-ethyl]-benzonitrile (BNE). The docked complex was further simulated for 10 ns using molecular dynamics simulation for stability. Thus, the molecular basis for curcumin binding to GGTase1 and FTase is reported.

Quantitative determination of cellular farnesyltransferase activity: towards defining the minimum substrate reactivity for biologically relevant protein farnesylation

Prenylation is a post-translational modification wherein an isoprenoid group is attached to a protein substrate by a protein prenyltransferase. Hundreds of peptide sequences are in vitro substrates for protein farnesyltransferase (FTase), but it remains unknown which of these sequences can successfully compete for in vivo prenylation. Translating in vitro studies to predict in vivo protein farnesylation requires determining the minimum reactivity needed for modification by FTase within the cell. Towards this goal, we developed a reporter protein series spanning several orders of magnitude in FTase reactivity as a calibrated sensor for endogenous FTase activity. Our approach provides a minimally invasive method to monitor changes in cellular FTase activity in response to environmental or genetic factors. Determining the reactivity "threshold" for in vivo prenylation will help define the prenylated proteome and identify prenylation-dependent pathways for therapeutic targeting.

Glucotoxic conditions induce endoplasmic reticulum stress to cause caspase 3 mediated lamin B degradation in pancreatic β-cells: protection by nifedipine

Nuclear lamins form the lamina on the interior of the nuclear envelope, and are involved in the regulation of various cellular processes, including DNA replication and chromatin organization. Despite this evidence, little is known about potential alterations in nuclear metabolism, specifically lamin structure and integrity in isolated β-cells subjected to stress conditions, including chronic exposure to hyperglycemia (i.e., glucotoxicity). Herein, we investigated effects of glucotoxic conditions on the catalytic activation of caspase 3 and the associated degradation of one of its substrate proteins, namely lamin-B. We report that incubation of insulin-secreting INS-1 832/13 cells, normal rat islets or human islets under glucotoxic conditions (20 mM; 12-48 h) results in the degradation of native lamin B leading to accumulation of the degraded products in non-relevant cellular compartments, including cytosol. Moreover, the effects of high glucose on caspase 3 activation and lamin B degradation were mimicked by thapsigargin, a known inducer of endoplasmic reticulum stress (ER stress). Nifedipine, a known blocker of calcium channel activation, inhibited high glucose-induced caspase 3 activation and lamin B degradation in these cells. 4-Phenyl butyric acid, a known inhibitor of ER stress, markedly attenuated glucose-induced CHOP expression (ER stress marker), caspase 3 activation and lamin B degradation. We conclude that glucotoxic conditions promote caspase 3 activation and lamin B degradation, which may, in part, be due to increased ER stress under these conditions. We also provide further evidence to support beneficial effects of calcium channel blockers against metabolic dysfunction of the islet β-cell induced by hyperglycemic conditions.

Syntheses of deuterium labeled prenyldiphosphate and prenylcysteine analogues for in vivo mass spectrometric quantification

A Wittig reaction employing Li(CD3)2CP(C6H5)3 was used to prepare d6-farnesol and d6-geranylgeraniol. Reductive amination of aniline-2,3,4,5,6-d5 was used to prepare the unnatural isoprenoid analogues d5-anilinogeraniol and d5-anilinofarnesol. All of these deuterated isoprenols were elaborated into their diphosphate and cysteine thioether derivatives suitable for use as stable-isotope labeled standards for quantitative mass spectrometric analysis.

Ras mutation and expression of farnesyltransferase β mRNA in Epstein-Barr virus-associated gastric carcinoma

AIM: To investigate ras gene mutations and farnesyltransferase (FTase) β mRNA expression in Epstein-Barr virus(EBV)-associated gastric carcinoma (EBVaGC), EBV-negative gastric carcinoma (EBVnGC) with matched clinico-pathological parameters and corresponding adjacent tissues of gastric carcinoma.

METHODS: The mutations of ras gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and the expression of FTase β mRNA was tested by reverse transcription PCR (RT-PCR) in 13 EBVaGCs, 45 EBVnGCs with matched clinicopathological parameters and 58 corresponding adjacent tissues of gastric carcinoma.

RESULTS: H-ras mutation at codon 12 was detected in 2(3.45%) cases of gastric carcinomas, both of which were EBVnGCs. No K-ras mutations occurred at codon 12 and 13 in all cases. The level of FTase β mRNA expression was 0.93 ± 0.39 in gastric carcinomas and 0.78 ± 0.26 in corresponding adjacent tissues, respectively. The difference between the two groups was significant (t = 2.44, P = 0.02). The level of FTase β mRNA expression was 0.80 ± 0.19 in EBVaGCs and 0.96 ± 0.43 in EBVnGCs respectively. The difference between the two groups was not significant (t = 1.93, P = 0.06). FTase β mRNA expression was not significantly different (t = 0.54, P = 0.60) between EBVaGCs and corresponding adjacent tissues either, while it was significant (t = 2.39, P = 0.02) between EBVnGCs and corresponding adjacent tissues. The level of FTase β mRNA expression had no significant relationship between 2 BHRF1 positive samples and 11 BHRF1 negetive samples of EBVaGCs (t = 0.26, P = 0.80) as well as between 6 BARF1 positive samples and 7 BARF1 negetive samples of EBVaGCs (t = 1.59, P = 0.14).

CONCLUSION: The frequency of ras gene mutations in gastric carcinomas is low in this study. The level of FTase β mRNA expression in gastric carcinomas is much higher than that in normal tissues. EBV infection has no significant correlations with ras mutations and FTase expression in EBVaGC.