The extractability of extracellular matrix components as a marker of cartilage remodeling in laryngeal squamous cell carcinoma

Sequential extraction was applied to investigate the proteoglycan (PG) organization in healthy laryngeal cartilage (HLC) and laryngeal cartilage squamous cell carcinoma (LCSCC). Highly stable aggrecan aggregates, extracted from both HLC and LCSCC with strong dissociative reagents, i.e., 4 M guanidine HCl (GdnHCl), represented 53% and 7%, respectively, of total extracted macromolecules. Less stable complexes/aggregates, extracted with mild dissociative reagents (1 and 2 M GdnHCl), represented 40% and 61% of total extracted PGs from healthy and cancerous cartilage, respectively. Interestingly, a relative high proportion (32%) of uronic acid (UA)-containing macromolecules were removed from the cancerous cartilage using associative extracting solutions (PBS and 0.5 M GdnHCl), which obviously represented molecules freely extractable from the tissue. In contrast, the corresponding proportion in HLC was impressively low (about 7%). The major proportion of these molecules was chondroitin sulfate-containing PGs (CSPGs), which identified mainly as aggrecan. Differential digestion of the sequential extracts with chondroitinase ABC and chondroitinase AC II demonstrated the presence of dermatan sulfate-containing PGs (DSPGs) in both HLC and LCSCC, being mainly present in the 1 M GdnHCl extract, and identified as decorin. All cancerous extracts were found to be rich in 4-sulfated disaccharides, mostly participating in DS structures. In conclusion, the applied procedure permitted the elucidation of the changes in the cartilage status, regarding the stability and identity of its proteoglycan aggregates/complexes, in both HLC and LCSCC.     

Specific transport of S-nitrosocysteine in human red blood cells: Implications for formation of S-nitrosothiols and transport of NO bioactivity within the vasculature

The transport of various S-nitrosothiols, NO and NO donors in human red blood cells (RBC) and the formation of erythrocytic S-nitrosoglutathione were investigated. Of the NO species tested only S-nitrosocysteine was found to form S-nitrosoglutathione in the RBC cytosol. L-Serine, L-cysteine and L-lysine inhibited formation of S-nitrosoglutathione. Incubation of RBC pre-incubated with S-[15N]nitroso-L-cysteine with native plasma or platelet-rich plasma led to formation of S-[15N]nitrosoalbumin and inhibited platelet aggregation, respectively. The specific transporter system of S-nitroso-L-cysteine in the RBC membrane may have implications for formation of S-nitrosoalbumin and S-nitrosohemoglobin and for transport of NO bioactivity within the vasculature.     

Phospholamban Gene Mutations Are Not Associated with Hypertrophic Cardiomyopathy in a Northern Greek Population

Hypertrophic cardiomyopathy (HCM) is a genetically transmitted cardiac disease characterized by unexplained myocardial hypertrophy and diverse clinical spectrum. Currently, more than 250 HCM-related mutations in 10 genes encoding contractile sarcomeric proteins have been identified. Phospholamban (PLN) is a modest modulator of intracellular Ca2+ homeostasis and may be a candidate gene responsible for cardiomyopathy. In this study 53 consecutive patients with HCM, coming from Northern Greece, were screened for mutations of PLN gene. The patients were evaluated by clinical history, physical examination, electrocardiogram and echocardiography. All PCR products were analyzed for mutation by both restriction analysis and sequencing. The systematic mutation screening did not reveal any mutation in exons 1 and 2 or in the promoter region of phospholamban gene. Additionally, no polymorphisms were detected in all patients. Therefore, PLN gene mutations were not found to be associated with HCM in a Northern Greece population.     

The G protein-coupled receptor rhodopsin in the native membrane

The higher-order structure of G protein-coupled receptors (GPCRs) in membranes may involve dimerization and formation of even larger oligomeric complexes. Here, we have investigated the organization of the prototypical GPCR rhodopsin in its native membrane by electron and atomic force microscopy (AFM). Disc membranes from mice were isolated and observed by AFM at room temperature. In all experimental conditions, rhodopsin forms structural dimers organized in paracrystalline arrays. A semi-empirical molecular model for the rhodopsin paracrystal is presented validating our previously reported results. Finally, we compare our model with other currently available models describing the supramolecular structure of GPCRs in the membrane.     

Rhodopsin signaling and organization in heterozygote rhodopsin knockout mice

Rhodopsin (Rho) resides within internal membrane structures called disc membranes that are found in the rod outer segments (ROS) of photoreceptors in the retina. Rho expression is essential for formation of ROS, which are absent in knockout Rho-/- mice. ROS of mice heterozygous for the Rho gene deletion (Rho+/-) may have a lower Rho density than wild type (WT) membranes, or the ROS structure may be reduced in size due to lower Rho expression. Here, we present evidence that the smaller volume of ROS from heterozygous mice is most likely responsible for observed electrophysiological response differences. In Rho+/- mice as compared with age-matched WT mice, the length of ROS was shorter by 30-40%, and the average diameter of ROS was reduced by approximately 20%, as demonstrated by transmission and scanning electron microscopy. Together, the reduction of the volume of ROS was approximately 60% in Rho+/- mice. Rho content in the eyes was reduced by approximately 43% and 11-cis-retinal content in the eye was reduced by approximately 38%, as determined by UV-visible spectroscopy and retinoid analysis, respectively. Transmission electron microscopy of negatively stained disc membranes from Rho+/- mice indicated a typical morphology apart from the reduced size of disc diameter. Power spectra calculated from disc membrane regions on such electron micrographs displayed a diffuse ring at approximately 4.5 nm(-1), indicating paracrystallinity of Rho. Atomic force microscopy of WT and Rho+/- disc membranes revealed, in both cases, Rho organized in paracrystalline and raftlike structures. From these data, we conclude that the differences in physiological responses measured in WT and Rho+/- mice are due to structural changes of the whole ROS and not due to a lower density of Rho.     

Modulation of angiogenesis-related protein synthesis by valproic acid

Recent studies have attested to the antiangiogenic effects of HDAC inhibitors on solid human tumors. The HDAC inhibitor butyrate has been reported to impair tumor-cell-induced angiogenesis. However, due to its poor bioavailability in vivo, the therapeutic use of butyrate is limited. On the other hand, valproic acid has inhibitory effects on carcinoma cells, is known to be well tolerated, and has an excellent bioavailability. We therefore set out to investigate whether the HDAC inhibitor valproic acid also impairs angiogenesis. Our findings indicate that valproic acid represses the relevant angiogenic factors VEGF and FGF in Caco-2 cells. Both, protein expression as well as mRNA levels of VEGF, were reduced to a similar degree. Suppression of ubiquitin-proteasome activity could be a possible reason for valproic acid effects on regulatory angiogenesis proteins. These results suggest that the HDAC inhibitor valproic acid could become a valuable new addition in the attempt to develop alternative therapeutic approaches in the treatment of colon carcinomas.     

Functional characterization of rhodopsin monomers and dimers in detergents

Rhodopsin (Rho) is a G protein-coupled receptor that initiates phototransduction in rod photoreceptors. High expression levels of Rho in the disc membranes of rod outer segments and the propensity of Rho to form higher oligomeric structures are evident from atomic force microscopy, transmission electron microscopy, and chemical cross-linking experiments. To explore the structural and functional properties of Rho in n-dodecyl-beta-maltoside, frequently used to purify heterologously expressed Rho and its mutants, we used gel filtration techniques, blue native gel electrophoresis, and functional assays. Here, we show that in micelles containing n-dodecyl-beta-maltoside at concentrations greater than 3 mM, Rho is present as a single monomer per detergent micelle. In contrast, in 12 mM 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulfonate (CHAPS), micelles contain mostly dimeric Rho. The cognate G protein transducin (Gt) appears to have a preference for binding to the Rho dimer, and the complexes fall apart in the presence of guanosine 5'-3-O-(thio)triphosphate. Cross-linked Rho dimers release the chromophore at a slower rate than monomers and are much more resistant to heat denaturation. Both Rho(*) monomers and dimers are capable of activating Gt, and both of them are phosphorylated by Rho kinase. Rho expressed in HEK293 cells is also readily cross-linked by a bifunctional reagent. These studies provide an explanation of how detergent influences the oligomer-dimermonomer equilibrium of Rho and describe the functional characterization of Rho monomers and dimers in detergent.