Kerem Teralı

New surprises from an old favourite: The emergence of telomerase as a key player in the regulation of cancer stemness.

It has been well established that the upregulation/reactivation of telomerase is a prerequisite for cellular immortalisation and malignant transformation. More significantly, perhaps, telomerase stands at the crossroads of multiple signalling pathways and its upregulation/reactivation leads to the modulation of critical cellular processes, including gene expression and metabolism. In recent years, this multifaceted ribonucleoprotein particle has become increasingly associated with the cancer stem cell (CSC) phenotype in various human cancers. Cancer stemness is a major contributor to therapy resistance and hence tumour recurrence. Here, we discuss new findings about the telomere-independent tumour-promoting functions of telomerase and provide a mechanistic explanation for its regulatory role in CSC biology. It is striking that there is a positive feedback loop between a number of gene products targeting telomerases reverse transcriptase subunit (TERT) and TERT expression itself. This plausibly amplifies the effects of central oncogenes and oncogenic pathways related to cancer stemness in a cell-autonomous fashion. A more complete elucidation of these regulatory mechanisms affords the opportunity to develop telomerase-focused therapies that differentiate or kill CSCs effectively.

The effect of the adaptor protein Isd11 on the quaternary structure of the eukaryotic cysteine desulphurase Nfs1

Small inorganic assemblies of alternating ferrous/ferric iron and sulphide ions, so-called iron-sulphur (Fe-S) clusters, are possibly natures most ancient prosthetic groups. One of the early actors in Fe-S cluster biosynthesis is a protein complex composed of a cysteine desulphurase, Nfs1, and its functional binding partner, Isd11. Although the essential function of Nfs1·Isd11 in the liberation of elemental sulphur from free cysteine is well established, little is known about its structure. Here, we provide evidence that shows Isd11 has a profound effect on the oligomeric state of Nfs1.

Turkish Cypriot paternal lineages bear an autochthonous character and closest resemblance to those from neighbouring Near Eastern populations

Abstract Background: Cyprus is an island in the Eastern Mediterranean Sea with a documented history of human settlements dating back over 10,000 years. Aim: To investigate the paternal lineages of a representative population from Cyprus in the context of the larger Near Eastern/Southeastern European genetic landscape. Subjects and methods: Three hundred and eighty samples from the second most populous ethnic group in Cyprus (Turkish Cypriots) were analysed at 17 Y-chromosomal short tandem repeat (Y-STR) loci. Results: A haplotype diversity of 0.9991 was observed, along with a number of allelic variants, multi-allelic patterns and a most frequent haplotype that have not previously been reported elsewhere. Pairwise genetic distance comparisons of the Turkish Cypriot Y-STR dataset and Y-chromosomal haplogroup distribution with those from Near East/Southeastern Europe both suggested a closer genetic connection with the Near Eastern populations. Median-joining network analyses of the most frequent haplogroups also revealed some evidence towards in situ radiation. Conclusion: Turkish Cypriot paternal lineages seem to bear an autochthonous character and closest genetic connection with the neighbouring Near Eastern populations. These observations are further underscored by the fact that the haplogroups associated with the spread of Neolithic Agricultural Revolution from the Fertile Crescent (E1b1b/J1/J2/G2a) dominate (>70%) the Turkish Cypriot haplogroup distribution.

Computational and experimental studies on the interaction between butyrylcholinesterase and fluoxetine: Implications in health and disease

Abstract Butyrylcholinesterase (BChE) is a serine esterase that plays a role in the detoxification of natural as well as synthetic ester-bond-containing compounds. Alterations in BChE activity are associated with a number of diseases. Cholinergic system abnormalities in particular are correlated with the formation of senile plaques in Alzheimer’s disease (AD), and administration of cholinesterase inhibitors is a common therapeutic approach used to treat AD. Here, our aim was to study the interaction between BChE and fluoxetine. Molecular docking simulations revealed that fluoxetine penetrated deep into the active-site gorge of BChE and that it was engaged in stabilizing noncovalent interactions with multiple subsites. In substrate kinetic studies, the Vm, Km, kcat and kcat/Km values were found to be 20.59 ± 0.36 U mg−1 protein, 194 ± 14 µM, 1.3 × 108 s−1 and 6.7 × 105 µM−1s−1, respectively. Based on inhibitory studies, fluoxetine appeared to inhibit BChE competitively, with an IC50 value of 104 µM and a Ki value of 36.3 ± 4.7 µM. Overall, both the low Ki value and the high number of BChE–fluoxetine interactions suggest that fluoxetine is a potent inhibitor of BChE, although in vivo mechanisms for the direct effects of BChE inhibition on various pathologies remain to be further investigated.

New insights into the interaction between mammalian butyrylcholinesterase and amitriptyline: a combined experimental and computational approach

Abstract Background Today, there is a growing recognition in the scientific community of the many roles of butyrylcholinesterase (BChE) in both physiological and pathological contexts. Objective Here, we aim at providing an accurate and comprehensive understanding of the mechanistic and structural aspects of mammalian BChE inhibition by the tricyclic antidepressant amitriptyline (AMI). Materials and methods The present work involves enzyme kinetic studies as well as protein–ligand docking and interaction profiling studies. Results We verify that AMI acts as an effective, mixed-type inhibitor of mammalian BChE, with an IC50 value of 10 μM and a Ki value of 2.25 μM. We also provide evidence showing that AMI penetrates deep into the active-site gorge of BChE where it interacts noncovalently with both the choline-binding and catalytic residues. Conclusion These findings could facilitate the prevention of the adverse metabolic sequelae of acquired BChE deficiency and also the design of new reversible anticholinesterase drugs.

An evaluation of neonicotinoids' potential to inhibit human cholinesterases: Protein–ligand docking and interaction profiling studies

Many so-called neuroactive insecticides target invertebrate neurotransmitter systems, including the cholinergic system. With their relatively low toxicity to vertebrates, neonicotinoids represent a new class of neuroactive insecticides that bind to nicotinic receptors for acetylcholine in the insect central nervous system and result in paralysis and eventual death due to receptor overstimulation. On the understanding that, today, cholinesterase inhibitors are used to obtain the symptomatic relief of Alzheimer disease (AD), the aforementioned direct cholinomimetic action of neonicotinoids could, perhaps, confer anti-AD drug-like attributes to these compounds. It is shown here, using protein-ligand docking and interaction profiling, that neonicotinoids penetrate deep into the active-site gorge of both acetylcholinesterase and butyrylcholinesterase and that they form relatively strong noncovalent bonds with multiple critical residues that normally bind/hydrolyze choline esters. With their gorge-spanning shape and dual-binding specificity, neonicotinoids (first-generation compounds in particular) represent promising leads for the development of reversible, mixed-type cholinesterase inhibitors in the fight against AD.

Evaluation of the inhibitory effect of abamectin on mammalian butyrylcholinesterase: Enzyme kinetic and molecular docking studies

ABSTRACT Abamectin, a blend of the natural avermectins B1a and B1b, is a widely-used insecticide/miticide with relatively low toxicity to mammals. Exposure to high doses of it, however, leads to cholinergic-like neurotoxic effects. Butyrylcholinesterase, which is best known for its abundant presence in plasma, is a serine hydrolase loosely coupled with the cholinergic system. It protects and supports the neurotransmitter function of its sister enzyme acetylcholinesterase. Here, using experimental and computational studies, we provide evidence demonstrating that abamectin is a potent (IC50 = 10.6 μM; Ki = 2.26 ± 0.35 μM) inhibitor of horse serum butyrylcholinesterase and that it interacts with the enzyme in a reversible, competitive manner predictively to block the mouth of the active-site gorge of the enzyme and to bind to several critical residues that normally bind/hydrolyze choline esters.

Mechanistic and structural insights into the in vitro inhibitory action of hypericin on glutathione reductase purified from baker's yeast

This work aims at studying the interaction between glutathione reductase (GR) and hypericin. The type of inhibition was determined by measuring changes in GR activity at increasing concentrations of hypericin as well as at varying concentrations of glutathione disulfide (GSSG) and nicotinamide adenine dinucleotide phosphate (NADPH), and the binding pose of hypericin was predicted by molecular docking. Accordingly, hypericin emerges as an effective inhibitor of GR. When the variable substrate is GSSG, the type of inhibition is competitive. When the variable substrate is NADPH, however, the type of inhibition appears to be linear mixed‐type competitive. Our computational analyses suggest that hypericin binds in the large intermonomer cavity of GR, and that it may interfere with the normal positioning/functioning of the redox‐active disulfide center at the enzymes active site. Overall, besides its contributory role in promoting oxidative stress via the formation of reactive oxygen species in photodynamic therapy, hypericin can also weaken cancer cells through inhibiting GR.

Assessment of the inhibitory activity of the pyrethroid pesticide deltamethrin against human placental glutathione transferase P1-1: A combined kinetic and docking study

Deltamethrin (DEL), which is a synthetic pyrethroid insecticide, has been used successfully all over the world to treat mosquito nets for the control of malaria. Glutathione S-transferases (GSTs; EC 2.5.1.18) catalyze the conjugation of reduced glutathione (GSH) to a variety of xenobiotics and are normally recognized as detoxification enzymes. Here, we used a colorimetric assay based on the human placental GSTP1-1 (hpGSTP1-1)-catalyzed reaction between GSH and the model substrate 1-chloro-2,4-dinitrobenzene (CDNB) as well as molecular docking to investigate the mechanistic and structural aspects of hpGSTP1-1 inhibition by DEL. We show that DEL is a potent, noncompetitive inhibitor of hpGSTP1-1 with an IC50 value of 6.1 μM and Ki values of 5.61 ± 0.32 μM and 7.96 ± 0.97 μM at fixed [CDNB]-varied [GSH] and fixed [GSH]-varied [CDNB], respectively. DEL appears to be accommodated well in an eccentric cavity located at the interface of the hpGSTP1-1 homodimer, presumably causing conformational changes to the enzymes substrate-binding sites such that the enzyme is no longer able to transform GSH and CDNB effectively. Correspondingly, considerable maternal exposure to and subsequent accumulation of DEL may interfere with the proper development of the vulnerable fetus, possibly increasing the risk of developing congenital defects.

Identification and characterization of a novel FBN1 gene variant in an extended family with variable clinical phenotype of Marfan syndrome

ABSTRACT Marfan syndrome (MFS) is a multi-systemic autosomal dominant condition caused by mutations in the gene (FBN1) coding for fibrillin-1. Mutations have been associated with a wide range of overlapping phenotypes. Here, we report on an extended family presenting with skeletal, ocular and cardiovascular clinical features. The 37-year-old male propositus, who had chest pain, dyspnea and shortness of breath, was first diagnosed based on the revised Ghent criteria and then subjected to molecular genetic analyses. FBN1 sequencing of the proband as well as available affected family members revealed the presence of a novel variant, c.7828G>C (p.Glu2610Gln), which was not present in any of the unaffected family members. In silico analyses demonstrated that the Glu2610 residue is part of the conserved DINE motif found at the beginning of each cbEGF domain of FBN1. The substitution of Glu2610 with Gln decreased fibrillin-1 production accordingly. Despite the fact that this variation appears to be primarily responsible for the etiology of MFS in the present family, our findings suggest that variable clinical expressions of the disease phenotype should be considered critically by the physicians.