Knockout of the folate transporter <Emphasis Type="Italic">folt-1</Emphasis> causes germline and somatic defects in <Emphasis Type="Italic">C. elegans</Emphasis>

Background  

The C. elegans gene folt-1 is an ortholog of the human reduced folate carrier gene. The FOLT-1 protein has been shown to transport folate and to be involved in uptake of exogenous folate by worms. A knockout mutation of the gene, folt-1(ok1460), was shown to cause sterility, and here we investigate the source of the sterility and the effect of the folt-1 knockout on somatic function.     

Role of reduced folate carrier in intestinal folate uptake

Studies from our laboratory and others have characterized different aspects of the intestinal folate uptake process and have shown that the reduced folate carrier (RFC) is expressed in the gut and plays a role in the uptake process. Little, however, is known about the actual contribution of the RFC system toward total folate uptake by the enterocytes. Addressing this issue in RFC knockout mice is not possible due to the embryonic lethality of the model. In this study, we describe the use of the new approach of lentivirus-mediated short hairpin RNA (shRNA) to selectively silence the endogenous RFC of the rat-derived intestinal epithelial cells (IEC-6), an established in vitro model for folate uptake, and examined the effect of such silencing on folate uptake. First we confirmed that the initial rate of [(3)H]folic acid uptake by IEC-6 cells was pH dependent with a markedly higher uptake at acidic compared with alkaline pH. We also showed that the addition of unlabeled folic acid to the incubation buffer leads to a severe inhibition ( approximately 95%) in [(3)H]folic acid (16 nM) uptake at buffer pH 5.5 but not at buffer pH 7.4. We then examined the effect of treating (for 72 h) IEC-6 cells with RFC-specific shRNA on the levels of RFC protein and mRNA and observed substantial reduction in the levels of both parameters ( approximately 80 and 78%, respectively). Such a treatment was also found to lead to a severe inhibition ( approximately 90%) in initial rate of folate uptake at buffer pH 5.5 (but not at pH 7.4); uptake of the unrelated vitamin, biotin, on the other hand, was not affected by such a treatment. These results demonstrate that the RFC system is the major (if not the only) folate uptake system that is functional in intestinal epithelial cells.     

Metabolic installation of thiols into sialic acid modulates adhesion and stem cell biology

Metabolic 'oligosaccharide engineering' methods based on N-acetyl-D-mannosamine (ManNAc) analogs allow the glycocalyx of living cells to be remodeled. Herein we report the analog Ac(5)ManNTGc (1) that enables thiols to be expressed in surface sialic acids. By locating this versatile functional group on the outer periphery of normally nonadhesive human Jurkat cells, we obtained spontaneous cell-cell clustering and attachment to complementary maleimide-derivatized substrates. When analyzed in human embryoid body-derived (hEBD) stem cells, Ac(5)ManNTGc induced beta-catenin expression and altered cell morphology, consistent with neuronal differentiation. Notably, these effects were modulated by the growth substrate of the cells, with a stronger response observed on a gold surface than on glass. Together, these results establish sugar analogs as small-molecule tools for tissue engineering by providing a method for attaching cells to scaffolds via their surface carbohydrates as well as offering a means to influence stem cell fates.     

A facile 1,3-dipolar cycloaddition of azomethine ylides to 2-arylidene-1,3-indanediones: synthesis of dispiro-oxindolylpyrrolothiazoles and their antimycobacterial evaluation

A facile 1,3-dipolar cycloaddition of azomethine ylide generated in situ from the reaction of 1,3-thiazolane-4-carboxylic acid and isatin to 2-arylidene-1,3-indanediones furnished novel dispiro-oxindolylpyrrolothiazoles regio- and stereo-selectively in moderate to good yields (60-92%). In vitro antitubercular screening of 27 compounds against Mycobacterium tuberculosis H37Rv (MTB) disclosed that spiro[5.3']-5'-nitrooxindolespiro-[6.3″]-1H-inden-1″,3″(2H)-dione-7-(4-bromophenyl)tetrahydro-1H-pyrrolo[1,2-c][1,3]thiazole has the maximum potency with a minimum inhibitory concentration (MIC) of 1.4 μM against MTB, being 3.4 and 5.4 times more potent than ciprofloxacin and ethambutol, respectively.     

Length‐dependent stability of α‐helical peptide upon adsorption to single‐walled carbon nanotube

Earlier studies have shown that the helical content of α‐helical peptide decreases upon its interaction with carbon nanotube (CNT). Further, the length of the α‐helix varies from few residues in the small globular protein to several number of residues in structural and membrane proteins. In structural and membrane proteins, helices are widely present as the supercoil i.e., helical bundles. Thus, in this study, the length‐dependent interaction pattern of α‐helical peptides with CNT and the stability of isolated α‐helical fragment versus supercoiled helical bundle upon interaction with CNT have been investigated using classical molecular dynamics (MD) simulation. Results reveal that the disruption in the helical motif on interaction with CNT is directly proportional to the length of the helix. Also it is found that the shorter helix does not undergo noticeable changes in the helicity upon adsorption with CNT. On the other hand, helicity of longer peptides is considerably affected by its interaction with CNT. In contrast to the known fact that the stability of the helix increases with its length, the disruption in the helical peptide increases with its length upon its interaction with CNT. Comparison of results shows that structural changes in the isolated helical fragment are higher than that in supercoiled helix. In fact, helical chain in supercoiled bundle does not undergo significant changes in the helicity upon interaction with CNT. Both the length of the helical peptide and the inherent stability of the helical unit in the supercoiled helix influence the interaction pattern with the CNT. © 2012 Wiley Periodicals, Inc. Biopolymers 99: 357–369, 2013.     

Enhancement of α-tocopherol content through transgenic and cell suspension culture systems in tobacco

The tocopherols are amphipathic antioxidant synthesized by photosynthetic organisms, which forms the essential component in the human diet. To increase the α-tocopherol content in tobacco, two approaches have been attempted in this study: (1) transgenic approach, by constitutive overexpression of the genes encoding Arabidopsis homogentisate phytyltransferase (HPT) and tocopherol cyclase (TC) through Agrobacterium-mediated genetic transformation; (2) non-transgenic approach, by supplementation of intermediates/precursors of vitamin E biosynthesis like tyrosine, p-hydroxyphenyl pyruvic acid, homogentisic acid (HGA) and phytol in different concentrations and combinations using cell suspension culture system. Molecular analyses by PCR, RT-PCR and Southern hybridization were carried out to confirm the HPT and TC expressing transgenic tobacco lines. The α-tocopherol content in transgenic plants expressing HPT and TC increase by 5.5 and 4.1, respectively, over the wild type. These results indicate that, HPT and TC activities are important in tobacco plants for enhancing the vitamin E content. In the second approach, the supplementation of precursor in cell suspension cultures, i.e., combination of 150 μM HGA + 100 μM phytol, showed the maximum enhancement of α-tocopherol, i.e., 36-fold. These findings clearly imply that enhancement of α-tocopherol levels in tobacco system is possible, if we could modulate the vitamin E metabolic pathway. This is a very useful finding for the large-scale production of natural Vitamin E. Among the two systems tested, cell suspension culture-based system is ideal over the transgenic technology due to its efficiency and no biosafety concerns.     

Diosgenin improves vascular function by increasing aortic eNOS expression, normalize dyslipidemia and ACE activity in chronic renal failure rats

In recent years, the role of endothelial dysfunction (ED) and excessive oxidative stress in the development of cardiovascular diseases has been highlighted. The aim of the present study is to evaluate the effect of diosgenin, an antioxidant on chronic renal failure (CRF) induced vascular dysfunction. CRF was induced by feeding the rats with a diet containing 0.75 % adenine and diosgenin was given orally (everyday at the dose of 40 mg/kg). Isometric force measurement was performed on isolated aortic rings in organ baths. Levels of reduced glutathione (GSH), nitric oxide metabolites, and endothelial nitric oxide synthase mRNA in rat aorta were examined. Further, plasma lipid profile, activity of enzymes of lipid metabolism, and aortic angiotensin converting enzyme (ACE) also studied. The overall results have proved that diosgenin attenuates CRF-induced impairment in acetylcholine induced endothelium-dependent and sodium nitroprusside induced endothelium-independent vascular relaxation. Moreover, it elevates the GSH and restores the eNOS mRNA expression level. CRF-induced dyslipidemia and ACE activity was also inhibited by diosgenin treatment. This study indicates that diosgenin have enough potential to protect vasculature against oxidative stress, dyslipidemia which in turn improves the vascular function in CRF milieu.     

Deciphering glycan linkages involved in Jurkat cell interactions with gold-coated nanofibers via sugar-displayed thiols

Metabolic oligosaccharide engineering (MOE) provides a method to install novel chemical functional groups into the glycocalyx of living cells. In this Letter we use this technology to compare the impact of replacing natural sialic acid, GalNAc, and GlcNAc with their thiol-bearing counterparts in Jurkat and HL-60 cells. When incubated in the presence of gold-coated nanofibers, only Jurkat cells incubated with Ac₅ManNTGc—an analogue that installs thiols into sialosides—experienced a distinctive ‘spreading’ morphology. The comparison of Ac₅ManNTGc with Ac₅GalNTGc and Ac₅GlcNTGc in the two cell lines implicated sialosides of N-linked glycans as critical molecular mediators of the unusual responses evoked in the Jurkat line.