A cyanobacterial hemoglobin with unusual ligand binding kinetics and stability properties

The glbN gene of the cyanobacterium Nostoc commune UTEX 584 encodes a hemoprotein, named cyanoglobin, that has high oxygen affinity. The basis for the high oxygen affinity of cyanoglobin was investigated through kinetic studies that utilized stopped-flow spectrophotometry and flash photolysis. Association and dissociation rate constants were measured at 20 degrees C for oxygen, carbon monoxide, nitric oxide, and methyl and ethyl isocyanides. The association rate constants for the binding of these five ligands to cyanoglobin are the highest reported for any naturally occurring hemoglobin, suggesting an unhindered and apolar ligand binding pocket. Cyanoglobin also shows high rates of autoxidation and hemin loss, indicating that the prosthetic group is readily accessible to solvent. The ligand binding behavior of cyanoglobin was more similar to that of leghemoglobin a than to that of sperm whale myoglobin. Collectively, the data support the model of cyanoglobin function described by Hill et al. [(1996) J. Bacteriol. 178, 6587-6598], in which cyanoglobin sequesters oxygen, and presents it to, or is a part of, a terminal cytochrome oxidase complex in Nostoc commune UTEX 584 under microaerobic conditions, when nitrogen fixation, and thus ATP demand, is maximal.     

Ipobscurines C and D: macrolactam-type indole alkaloids from the seeds of Ipomoea obscura

Separation of the methanolic seed extract of Ipomoea obscura afforded five indole alkaloids, three of them (ipobscurines B-D) being new natural products of a unique structural type characterized as serotonin hydroxycinnamic acid amide-type conjugates with a second phenylpropanoid moiety forming an ether with the 5-OH position of the indole nucleus. Due to an oxidative phenolic coupling between the two phenylpropanoid moieties of the supposed precursor ipobscurine B two 21-membered macrolactams with a phenol ether partial structure are formed: the trans-cis isomers ipobscurines C and D. Their structures were established on the basis of spectral data. Moreover, total synthesis of the racemic erythro- and threo-ipobscurine B 4',4"-dimethyl ethers and the comparison with the corresponding derivative of natural (-)-ipobscurine B proved an erythro configuration of the latter.     

Pergolide, terguride and N,N'-spacer-linked oligomers of both interact with 5-HT2A receptors of rat tail artery

Pergolide, terguride and N,N'-spacer-linked oligomers of both have been tested for their ability to interact with 5 hydroxytryptamine(HT)2A receptors of rat tail artery. Pergolide was a potent partial agonist (pEC50 7.5, Emax 55 %) and antagonized 5-HT-induced contractions (pKp 7.2). Pergolide dimer 3 with a p-xylene spacer between the indole nitrogens (N-1) displayed somewhat lower agonist potency than pergolide (pEC50 7.0, Emax 55 %, pKp 6.6). The contractile responses to pergolide and dimer 3 were antagonized by the 5-HT2A receptor antagonist ketanserin (pA2 9.4, 9.1). In contrast to pergolide dimer 3, pergolide dimers 5 and 9 with an alkyl and an aralkyl spacer between the piperidine nitrogens (N-6) lacked agonism and displayed low affinity at 5-HT2A receptors (pA2 < 5.5). Terguride behaved as an insurmountable antagonist of 5-HT (pA2 8.4). Oligomers of terguride showed 5 to 50-fold lower affinity. It is concluded that pergolide and terguride show a high affinity for 5-HT2A receptors, but dimerization (oligomerization) of both drugs fails to increase affinity.     

CD133 Expression Is Not Synonymous to Immunoreactivity for AC133 and Fluctuates throughout the Cell Cycle in Glioma Stem-Like Cells

A transmembrane protein CD133 has been implicated as a marker of stem-like glioma cells and predictor for therapeutic response in malignant brain tumours. CD133 expression is commonly evaluated by using antibodies specific for the AC133 epitope located in one of the extracellular domains of membrane-bound CD133. There is conflicting evidence regarding the significance of the AC133 epitope as a marker for identifying stem-like glioma cells and predicting the degree of malignancy in glioma cells. The reasons for discrepant results between different studies addressing the role of CD133/AC133 in gliomas are unclear. A possible source for controversies about CD133/AC133 is the widespread assumption that expression patterns of the AC133 epitope reflect linearly those of the CD133 protein. Consequently, the readouts from AC133 assessments are often interpreted in terms of the CD133 protein. The purpose of this study is to determine whether and to what extent do the readouts obtained with anti-AC133 antibody correspond to the level of CD133 protein expressed in stem-like glioma cells. Our study reveals for the first time that CD133 expressed on the surface of glioma cells is poorly immunoreactive for AC133. Furthermore, we provide evidence that the level of CD133 occupancy on the surface of glioma cells fluctuates during the cell cycle. Our results offer a new explanation for numerous inconsistencies regarding the biological and clinical significance of CD133/AC133 in human gliomas and call for caution in interpreting the lack or presence of AC133 epitope in glioma cells.     

Biosimilars 2.0: Guiding principles for a global “patients first” standard

In the European Union, biosimilar products have been approved since 2006 under an abbreviated pathway that leverages their similarity to an existing “reference” biological product. The products approved to date are based on recombinant versions of endogenous proteins with well-understood structures and pharmacology, but complicated safety and immunogenicity profiles. The period during the 2000s that included the first reviews, approvals, sale and use of biosimilars is referred to herein as “Biosimilars 1.0.” Over the next several years, a new and advanced tranche of biosimilars will be developed for complex reference products, including medicines used in the treatment of cancer and autoimmune diseases. A global market for biosimilars is developing and this may well foreshadow the beginning of the second era of product development. This Biosimilars 2.0 period will likely be characterized by the development of complex products, global harmonization of standards and the increasing demand for long-term monitoring of pharmaceuticals. The products developed in this period should exhibit high levels of fidelity to the reference products and should be rigorously evaluated in analytical, non-clinical and clinical comparisons. Additionally, Biosimilars 2.0 manufacturers should strive for transparency in their labels and take proactive strides to be accountable to providers and patients for the quality of their products. An important opportunity now exists for the healthcare community, industry and regulators to work in partnership, to outline the appropriate standards for these products and to facilitate increased access while meeting patients'' needs.Key words: biotechnology, biosimilars, generic drugs, monoclonal antibodies, pharmacodynamics, pharmacokinetics     

GABA and glutamate specifically induce contractions in the sponge <Emphasis Type="Italic">Tethya wilhelma</Emphasis>

Sponges (Porifera) are nerve- and muscleless. Nevertheless, they react to external stimuli in a coordinated way, by body contraction, oscule closure or stopping pumping activity. The underlying mechanisms are still unknown, but evidence has been found for chemical messenger-based systems. We used the sponge Tethya wilhelma to test the effect of γ-aminobutyric acid (GABA) and glutamate (l-Glu) on its contraction behaviour. Minimal activating concentrations were found to be 0.5 μM (GABA) and 50 μM (l-Glu), respectively. Taking maximum relative contraction speed and minimal relative projected body area as a measure of the sponge’s response, a comparison of the dose–response curves indicated a higher sensitivity of the contractile tissue for GABA than for l-Glu. The concentrations eliciting the same contractile response differ by about 100-fold more than the entire concentration range tested. In addition, desensitising effects and spasm-like reactions were observed. Presumably, a GABA/l-Glu metabotropic receptor-based system is involved in the regulation of contraction in T. wilhelma. We discuss a coordination system for sponges based on hypothetical chemical messenger pathways. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. K. Ellwanger and A. Eich contributed equally and designed and performed experiments, analysed data and revised the paper, M. Nickel designed the study and experiments, analysed data, prepared the figures, wrote and revised the paper.     

Lysosomal storage disorder in non-immunological hydrops fetalis (NIHF) - more common than assumed? Report of four cases with transient NIHF and a review of the literature

Background

Lysosomal storage disorders (LSD) are a rare cause of non immunological hydrops fetalis (NIHF) and congenital ascites. The reported incidence is about 1%. The incidence of idiopathic NIHF is estimated to be about 18%.

Patients and methods

We report four cases with transient hydrops fetalis resulting from LSD and performed a literature review on LSD with NIHF and congenital ascites in combination.

Results

At present, 12 different LSDs are described to be associated with NIHF or congenital ascites. Most patients had a family history of NIHF, where the preceding sibling had not been examined. A diagnostic approach to the fetus with NIHF due to suspected LSD either in utero or postnatal is suggested. Transient forms of NIHF and/or ascites in association with MPS IVA, MPS VII and NPC are described for the first time in this publication.

Conclusions

LSD should be considered in transient hydrops. Enzymatic studies in chorionic villous sample or amniotic cultured cells, once the most common conditions associated with fetal ascites or hydrops have been ruled out, are important. This paper emphasizes the fact that LSD is significantly higher than the estimated 1% in previous studies, which is important for genetic counseling as there is a high risk of recurrence and the availability of enzyme replacement therapy for an increasing number of LSD.

     

Spondylocheiro dysplastic form of the Ehlers-Danlos syndrome--an autosomal-recessive entity caused by mutations in the zinc transporter gene SLC39A13

We present clinical, radiological, biochemical, and genetic findings on six patients from two consanguineous families that show EDS-like features and radiological findings of a mild skeletal dysplasia. The EDS-like findings comprise hyperelastic, thin, and bruisable skin, hypermobility of the small joints with a tendency to contractures, protuberant eyes with bluish sclerae, hands with finely wrinkled palms, atrophy of the thenar muscles, and tapering fingers. The skeletal dysplasia comprises platyspondyly with moderate short stature, osteopenia, and widened metaphyses. Patients have an increased ratio of total urinary pyridinolines, lysyl pyridinoline/hydroxylysyl pyridinoline (LP/HP), of approximately 1 as opposed to approximately 6 in EDS VI or approximately 0.2 in controls. Lysyl and prolyl residues of collagens were underhydroxylated despite normal lysyl hydroxylase and prolyl 4-hydroxylase activities; underhydroxylation was a generalized process as shown by mass spectrometry of the alpha1(I)- and alpha2(I)-chain-derived peptides of collagen type I and involved at least collagen types I and II. A genome-wide SNP scan and sequence analyses identified in all patients a homozygous c.483_491 del9 SLC39A13 mutation that encodes for a membrane-bound zinc transporter SLC39A13. We hypothesize that an increased Zn(2+) content inside the endoplasmic reticulum competes with Fe(2+), a cofactor that is necessary for hydroxylation of lysyl and prolyl residues, and thus explains the biochemical findings. These data suggest an entity that we have designated "spondylocheiro dysplastic form of EDS (SCD-EDS)" to indicate a generalized skeletal dysplasia involving mainly the spine (spondylo) and striking clinical abnormalities of the hands (cheiro) in addition to the EDS-like features.