How sugars convey information on protein conformation in the endoplasmic reticulum

The N-glycan-dependent quality control of glycoprotein folding prevents endoplasmic reticulum to Golgi exit of folding intermediates, irreparably misfolded glycoproteins and not completely assembled multimeric complexes. It also enhances folding efficiency by preventing aggregation and facilitating formation of proper disulfide bonds. The control mechanism essentially involves four components, resident lectin-chaperones that recognize monoglucosylated polymannose glycans, a lectin-associated oxidoreductase acting on monoglucosylated glycoproteins, a glucosyltransferase and a glucosidase that creates monoglucosylated epitopes in glycans transferred in protein N-glycosylation or removes the glucose units added by the glucosyltransferase. This last enzyme is the only mechanism component sensing glycoprotein conformations as it creates monoglucosylated glycans exclusively in not properly folded species or in not completely assembled complexes. The purpose of the review is to describe the most significant recent findings on the mechanism of glycoprotein folding and assembly quality control and to discuss the main still unanswered questions.     

Oxidative stress and antioxidant defence in a healthy nonagenarian population

Results on oxidative markers during ageing are not consistent throughout the scientific literature; however, successful ageing may depend on better ability to cope with oxidative stress. A previous study of ours showed that successful ageing could actually be related to enhanced response to oxidatively modified proteins. In this study, a healthy nonagenarian population (OVER-90) was examined for various blood oxidative biomarkers and compared with a healthy population of blood donors (age range, 23-66 years). Blood glutathione, both total (tGSH) and oxidised (GSSG), and total plasmatic antioxidant status were maintained in the OVER-90 at a level similar to the control population. Sulphydryl (sulfhydryl) groups and glutathione peroxidase (GPx) were instead decreased. The results are discussed in a possible unifying view: the OVER-90 population could possess a globally preserved antioxidant ability, though some signs of oxidative damage are present and some structures could be 'sacrificed' in order to keep the redox equilibrium.     

Post-Golgi protein traffic in the plant secretory pathway

The Golgi apparatus in plants is organized as a multitude of individual stacks that are motile in the cytoplasm and in close association with the endoplasmic reticulum (ER) (Boevink et al. in Plant J 15:441–447, 1998). These stacks operate as a sorting centre for cargo molecules, providing modification and redirection to other organelles as appropriate. In the post-Golgi direction, these include vacuole and plasma membrane, and specialized transport routes to each are required to prevent mislocalization. Recent evidence in plant cells points to the existence of post-Golgi organelles that function as intermediate stations for efficient protein traffic, as well as to the influence of small GTPases such as Rabs and ARFs on post-Golgi trafficking. This review focuses on the latest findings on post-Golgi trafficking routes and on the involvement of GTPases and their effectors on the trafficking of proteins in the plant secretory pathway. Sally L. Hanton and Loren A. Matheson have contributed equally to this work.     

Functionalized titanium oxide surfaces with phosphated carboxymethyl cellulose: characterization and bonelike cell behavior

The performance of dental or orthopedic implants is closely dependent on surface properties in terms of topography and chemistry. A phosphated carboxymethylcellulose containing one phosphate group for each disaccharide unit was synthesized and used to functionalize titanium oxide surfaces with the aim to improve osseointegration with the host tissue. The modified surfaces were chemically characterized by means of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The investigation of the surface topography was performed by atomic force microscopy measurements before and after the polysaccharide coating. In vitro biological tests using osteoblastlike cells demonstrated that functionalized TiO(2) surfaces modulated cell response, in terms of adhesion, proliferation,and morphology. Phosphated carboxymethylcellulose promoted better cell adhesion and significantly enhanced their proliferation. The morphology of cells was polygonal and more spread on this type of modified surface.These findings suggest that the presence of a phosphate polysaccharide coating promotes osteoblast growth on the surface potentially improving biomaterial osseointegration.     

Genetic Analysis of Connective Tissue Growth Factor as an Effector of Transforming Growth Factor β Signaling and Cardiac Remodeling

The matricellular secreted protein connective tissue growth factor (CTGF) is upregulated in response to cardiac injury or with transforming growth factor β (TGF-β) stimulation, where it has been suggested to function as a fibrotic effector. Here we generated transgenic mice with inducible heart-specific CTGF overexpression, mice with heart-specific expression of an activated TGF-β mutant protein, mice with heart-specific deletion of Ctgf, and mice in which Ctgf was also deleted from fibroblasts in the heart. Remarkably, neither gain nor loss of CTGF in the heart affected cardiac pathology and propensity toward early lethality due to TGF-β overactivation in the heart. Also, neither heart-specific Ctgf deletion nor CTGF overexpression altered cardiac remodeling and function with aging or after multiple acute stress stimuli. Cardiac fibrosis was also unchanged by modulation of CTGF levels in the heart with aging, pressure overload, agonist infusion, or TGF-β overexpression. However, CTGF mildly altered the overall cardiac response to TGF-β when pressure overload stimulation was applied. CTGF has been proposed to function as a critical TGF-β effector in underlying tissue remodeling and fibrosis throughout the body, although our results suggest that CTGF is of minimal importance and is an unlikely therapeutic vantage point for the heart.     

Platelet‐Rich Plasma Increases Growth and Motility of Adipose Tissue‐Derived Mesenchymal Stem Cells and Controls Adipocyte Secretory Function

Adipose tissue‐derived mesenchymal stem cells (Ad‐MSC) and platelet derivatives have been used alone or in combination to achieve regeneration of injured tissues. We have tested the effect of platelet‐rich plasma (PRP) on Ad‐MSC and adipocyte function. PRP increased Ad‐MSC viability, proliferation rate and G1‐S cell cycle progression, by at least 7‐, 2‐, and 2.2‐fold, respectively, and reduced caspase 3 cleavage. Higher PRP concentrations or PRPs derived from individuals with higher platelet counts were more effective in increasing Ad‐MSC growth. PRP also accelerated cell migration by at least 1.5‐fold. However, PRP did not significantly affect mature adipocyte viability, differentiation and expression levels of PPAR‐γ and AP‐2 mRNAs, while it increased leptin production by 3.5‐fold. Interestingly, PRP treatment of mature adipocytes also enhanced the release of Interleukin (IL)‐6, IL‐8, IL‐10, Interferon‐γ, and Vascular Endothelial Growth Factor. Thus, data are consistent with a stimulatory effect of platelet derivatives on Ad‐MSC growth and motility. Moreover, PRP did not reduce mature adipocyte survival and increased the release of pro‐angiogenic factors, which may facilitate tissue regeneration processes. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc. J. Cell. Biochem. 116: 2408–2418, 2015. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc.     

Monomeric and Dimeric 9‐O Anthraquinone and Phenanthryl Derivatives of Cinchona Alkaloids as Chiral Solvating Agents for the NMR Enantiodiscrimination of Chiral Hemiesters

Mono‐ and bis‐alkaloid chiral auxiliaries with anthraquinone or phenanthryl cores were probed as chiral solvating agents (CSAs) for the enantiodiscrimination of chiral cyclic hemiesters. The dimeric anthraquinone derivative and the monomeric phenanthryl one showed remarkable efficiency in the nuclear magnetic resonance (NMR) differentiation of enantiomeric mixtures of hemiesters. An anthraquinone analogous with a single alkaloid unit was remarkably less effective. The conformational prevalence of the chiral auxiliaries were ascertained by NMR. Chirality 27:693–699, 2015. © 2015 Wiley Periodicals, Inc.     

CGR2 and CGR3 have critical overlapping roles in pectin methylesterification and plant growth in Arabidopsis thaliana

Pectins are critical polysaccharides of the cell wall that are involved in key aspects of a plant's life, including cell‐wall stiffness, cell‐to‐cell adhesion, and mechanical strength. Pectins undergo methylesterification, which affects their cellular roles. Pectin methyltransferases are believed to methylesterify pectins in the Golgi, but little is known about their identity. To date, there is only circumstantial evidence to support a role for QUASIMODO2 (QUA2)‐like proteins and an unrelated plant‐specific protein, cotton Golgi‐related 3 (CGR3), in pectin methylesterification. To add to the knowledge of pectin biosynthesis, here we characterized a close homolog of CGR3, named CGR2, and evaluated the effect of loss‐of‐function mutants and over‐expression lines of CGR2 and CGR3 in planta. Our results show that, similar to CGR3, CGR2 is a Golgi protein whose enzyme active site is located in the Golgi lumen where pectin methylesterification occurs. Through phenotypical analyses, we also established that simultaneous loss of CGR2 and CGR3 causes severe defects in plant growth and development, supporting critical but overlapping functional roles of these proteins. Qualitative and quantitative cell‐wall analytical assays of the double knockout mutant demonstrated reduced levels of pectin methylesterification, coupled with decreased microsomal pectin methyltransferase activity. Conversely, CGR2 and CGR3 over‐expression lines have markedly opposite phenotypes to the double knockout mutant, with increased cell‐wall methylesterification levels and microsomal pectin methyltransferase activity. Based on these findings, we propose that CGR2 and CGR3 are critical proteins in plant growth and development that act redundantly in pectin methylesterification in the Golgi apparatus.