BBA - Molecular Basis of Disease (v.1639, #2)

Lipopolysaccharides of Vibrio cholerae by S.N. Chatterjee; Keya Chaudhuri (65-79).
Vibrio cholerae is the causative organism of the disease cholera. The lipopolysaccharide (LPS) of V. cholerae plays an important role in eliciting the antibacterial immune response of the host and in classifying the vibrios into some 200 or more serogroups. This review presents an account of our up-to-date knowledge of the physical and chemical characteristics of the three constituents, lipid-A, core-polysaccharide (core-PS) and O-antigen polysaccharide (O-PS), of the LPS of V. cholerae of different serogroups including the disease-causing ones, O1 and O139. The structure and occurrence of the capsular polysaccharide (CPS) on V. cholerae O139 have been discussed as a relevant topic. Similarity and dissimilarity between the structures of LPS of different serogroups, and particularly between O22 and O139, have been analysed with a view to learning their role in the causation of the epidemic form of the disease by avoiding the host defence mechanism and in the evolution of the newer pathogenic strains in future. An idea of the emerging trends of research involving the use of immunogens prepared from synthetic oligosaccharides that mimic terminal epitopes of the O-PS of V. cholerae O1 in the development of a conjugate anti cholera vaccine is also discussed.
Keywords: Vibrio cholerae; Serogroup; Lipopolysaccharide; Capsular polysaccharide; Structure;

Tryptophan hydroxylase expression in human skin cells by Andrzej Slominski; Alexander Pisarchik; Olle Johansson; Chen Jing; Igor Semak; George Slugocki; Jacobo Wortsman (80-86).
We attempted to further characterize cutaneous serotoninergic and melatoninergic pathways evaluating the key biosynthetic enzyme tryptophan hydroxylase (TPH). There was wide expression of TPH mRNA in whole human skin, cultured melanocytes and melanoma cells, dermal fibroblasts, squamous cell carcinoma cells and keratinocytes. Gene expression was associated with detection of TPH immunoreactive species by Western blotting. Characterization of the TPH immunoreactive species performed with two different antibodies showed expression of the expected protein (55–60 kDa), and of forms with higher and lower molecular weights. This pattern of broad spectrum of TPH expression including presumed degradation products suggests rapid turnover of the enzyme, as previously reported in mastocytoma cells. RP-HPLC of skin extracts showed fluorescent species with the retention time of serotonin and N-acetylserotonin. Immunocytochemistry performed in skin biopsies localized TPH immunoreactivity to normal and malignant melanocytes. We conclude that while the TPH mRNA and protein are widely expressed in cultured normal and pathological epidermal and dermal skin cells, in vivo TPH expression is predominantly restricted to cells of melanocytic origin.
Keywords: Tryptophan hydroxylase; Serotonin; Skin; Melanocyte; Keratinocyte; Fibroblast;

Congenital afibrinogenemia: intracellular retention of fibrinogen due to a novel W437G mutation in the fibrinogen Bβ-chain gene by Silvia Spena; Rosanna Asselta; Stefano Duga; Massimo Malcovati; Flora Peyvandi; Pier Mannuccio Mannucci; Maria Luisa Tenchini (87-94).
Congenital afibrinogenemia is a rare autosomal recessive coagulation disorder characterised by hemorrhagic manifestations of variable entity and by severe plasma fibrinogen deficiency. Among the 31 afibrinogenemia-causing mutations so far reported, only 2 are missense mutations and both are located in the fibrinogen Bβ-chain gene.Direct sequencing of the fibrinogen gene cluster in two afibrinogenemic Iranian siblings revealed a novel homozygous T>G transversion in exon 8 (nucleotide position 8025) of the fibrinogen Bβ-chain gene. The resulting W437G missense mutation involves a highly conserved amino acid residue, located in the C-terminal globular D domain. The role of the W437G amino acid substitution on fibrinogen synthesis, folding, and secretion was assessed by in vitro expression experiments in COS-1 cells, followed by qualitative and quantitative analyses of intracellular and secreted mutant fibrinogen. Results of both pulse-chase experiments and enzyme-linked immunosorbent assays demonstrated intracellular retention of the mutant W437G fibrinogen and marked reduction of its secretion.These data, besides elucidating the pathogenetic role of the W437G mutation in afibrinogenemia, underline the importance of the Bβ-chain D domain in fibrinogen folding and secretion.
Keywords: Congenital afibrinogenemia; Fibrinogen Bβ-chain; Missense mutation; Protein in vitro expression;

Mucopolysaccharidosis type I (MPS I; McKusick 25280; Hurler syndrome, Hurler–Scheie syndrome and Scheie syndrome) is caused by a deficiency in the lysosomal hydrolase, α-l-iduronidase (EC 3.2.1.76). MPS I patients present within a clinical spectrum bounded by the extremes of Hurler and Scheie syndromes. The α-l-iduronidase missense mutations R89Q and R89W were investigated and altered an important arginine residue proposed to be a nucleophile activator in the catalytic mechanism of α-l-iduronidase. The R89Q α-l-iduronidase mutation was shown to result in a reduced level of α-l-iduronidase protein (≤10% of normal control) compared to a normal control level of α-l-iduronidase protein that was detected for the R89W α-l-iduronidase mutation. When taking into account α-l-iduronidase specific activity, the R89W mutation had a greater effect on α-l-iduronidase activity than the R89Q mutation. However, overall the R89W mutation produced more residual α-l-iduronidase activity than the R89Q mutation. This was consistent with MPS I patients, with an R89W allele, having a less severe clinical presentation compared to MPS I patients with either a double or single allelic R89Q mutation. The effects of the R89Q and R89W mutations on enzyme activity supported the proposed role of R89 as a nucleophile activator in the catalytic mechanism of α-l-iduronidase.
Keywords: α-l-Iduronidase; Hurler syndrome; Mucopolysaccharidosis I; Mutant protein; Lysosomal storage disorder; Catalytic efficiency; Glycoside hydrolase;

The RING-H2 protein RNF11 is differentially expressed in breast tumours and interacts with HECT-type E3 ligases by Richard Kitching; Michael J. Wong; David Koehler; Angelika M. Burger; Goran Landberg; Gerald Gish; Arun Seth (104-112).
A breast cancer-associated mRNA originally cloned as a 475-bp partial cDNA from a library enriched for tumour cDNAs [Oncogene 16 (1998) 327] is expressed at high levels in breast and prostate cancer cells. Immunohistochemical analysis indicates that the protein is expressed in primary breast tumours. We used RT-PCR to generate a full-length 2852 nt mRNA sequence that includes the hypothetical open reading frame (ORF) for human RNF11. Our analysis shows that RNF11 encodes modular domains and motifs likely to interact with other proteins involved in oncogenesis. Chief among these are the RING-H2 finger domain that could facilitate the degradation of specific substrate(s) involved in oncogenesis and the PY motif which binds to WW-domain proteins, several of which are known to be E3 ubiquitin ligases. Our GST-pulldown and immunoprecipitation results indicate that RNF11 interacts with the E3 ligase AIP4 when coexpressed with RNF11 in mammalian cells.
Keywords: WW-domain; PY motif; Breast cancer; RNF11; Protein:protein interaction;

Diabetes induces metabolic adaptations in rat liver mitochondria: role of coenzyme Q and cardiolipin contents by Fernanda M. Ferreira; Raquel Seiça; Paulo J. Oliveira; Pedro M. Coxito; António J. Moreno; Carlos M. Palmeira; Maria S. Santos (113-120).
Several studies have been carried out to evaluate the alterations in mitochondrial functions of diabetic rats. However, results are sometimes controversial, since experimental conditions diverge, including age and strain of used animals. The purpose of this study was to evaluate the metabolic modifications in liver mitochondria, both in the presence of severe (STZ-treated rats) and mild hyperglycaemia [Goto–Kakizaki (GK) rats], when compared with control animals of similar age. Moreover, metabolic alterations were evaluated also at initial and advanced stages of the disease.We observed that both models of diabetes (type 1 and type 2) presented a decreased susceptibility of liver mitochondria to the induction of permeability transition (MPT). Apparently, there is a positive correlation between the severity of diabetes mellitus (and duration of the disease) and the decline in the susceptibility to MPT induction. We also found that liver mitochondria isolated from diabetic rats presented some metabolic adaptations, such as an increase in coenzyme Q and cardiolipin contents, that can be responsible for the observed decrease in the susceptibility to multiprotein pore (MPTP) opening.
Keywords: Diabetes mellitus; Type 1 diabetes; Type 2 diabetes; Goto–Kakizaki (GK) rat; Streptozotocin-induced diabetic (STZ) rat; Mitochondrial permeability transition (MPT);

Increased formation of methylglyoxal and protein glycation, oxidation and nitrosation in triosephosphate isomerase deficiency by Naila Ahmed; Sinan Battah; Nikolaos Karachalias; Roya Babaei-Jadidi; Margit Horányi; Klára Baróti; Susan Hollan; Paul J. Thornalley (121-132).
Triosephosphate isomerase deficiency is associated with the accumulation of dihydroxyacetonephosphate (DHAP) to abnormally high levels, congenital haemolytic anaemia and a clinical syndrome of progressive neuromuscular degeneration leading to infant mortality. DHAP degrades spontaneously to methylglyoxal (MG)—a potent precursor of advanced glycation endproducts (AGEs). MG is detoxified to d-lactate intracellularly by the glyoxalase system. We investigated the changes in MG metabolism and markers of protein glycation, oxidation and nitrosation in a Hungarian family with two germline identical brothers, compound heterozygotes for triosephosphate isomerase deficiency, one with clinical manifestations of chronic neurodegeneration and the other neurologically intact. The concentration of MG and activity of glyoxalase I in red blood cells (RBCs) were increased, and the concentrations of d-lactate in blood plasma and d-lactate urinary excretion were also increased markedly in the propositus. There were concomitant increases in MG-derived AGEs and the oxidative marker dityrosine in hemoglobin. Smaller and nonsignificant increases were found in the neurologically unaffected brother and parents. There was a marked increase (15-fold) in urinary excretion of the nitrosative stress marker 3-nitrotyrosine in the propositus. The increased derangement of MG metabolism and associated glycation, oxidative and nitrosative stress in the propositus may be linked to neurodegenerative process in triosephosphate isomerase deficiency.
Keywords: Triosephosphate isomerase; Dihydroxyacetonephosphate; Methylglyoxal; Advanced glycation endproduct; Glyoxalase; Neuromuscular degeneration; Oxidative stress;

Inhibition by Aplidine of the aggregation of the prion peptide PrP 106–126 into β-sheet fibrils by Mar Pérez; Mourad Sadqi; Victor Muñoz; Jesús Ávila (133-139).
Aplidine, a cyclic peptide, from the tunicate Aplidium albican, prevents the in vitro aggregation into β-sheet containing fibrils of the prion peptide 106–126 when co-incubated in a 1:1 molar ratio. The blocking of fibril formation induced by Aplidine has clear sequence specificity, being much stronger for the 106–126 prion peptide than for the β-amyloid 25–35 peptide. In addition to the known ability of Aplidine to cross the plasmatic membrane, these results indicate that Aplidine is a potential leading compound for the development of therapeutic blockers of prion aggregation.
Keywords: Aplidine; Prion peptide; Inhibition of aggregation;