Biomedical subjects

Olaf Scheibner

Publications and source records attributed to Olaf Scheibner.

5 recordsLinked to original sources

PubMed2007

Peptidomics of identified neurons demonstrates a highly differentiated expression pattern of FXPRLamides in the neuroendocrine system of an insect.

FXPRLamides are insect neuropeptides that mediate such diverse functions as pheromone biosynthesis, visceral muscle contraction, and induction of diapause. Although multiple forms occur in every insect studied so far, little is known about a possible functional differentiation and/or differences in the cellular expression pattern of these messenger molecules. In this study, we performed a mass spectrometric survey of all FXPRLamide-expressing neurosecretory neurons in the CNS of Periplaneta americana. That species combines a very well characterized peptidergic system with relatively easy accessible neurosecretory cells suitable for dissection. In addition to the extensive mass spectrometric analyses of single cells, the projection of the FXPRLamide-expressing neurons was studied with three antisera specifically recognizing different FXPRLamides. The following conclusions can be drawn from this first comprehensive peptidomic approach on insect neurons. 1) A high degree of differentiation in the expression of FXPRLamides exists; not fewer then four cell types containing different sets of FXPRLamides were observed. 2) A low level of colocalization with other neuropeptides was found in these neurons. 3) A comparison with FXPRLamide-expressing neurons of other insects shows a high degree of conservation in the localization and projection of these neurons, which is not corroborated by a similar conservation of the corresponding peptide sequences. 4) Although the methods for cell identification, dissection, and sample preparation for mass spectrometry were kept as simple as possible, it was unambiguously shown that this approach is generally suitable for routine analysis of single identified neurons of insects.

Animals↗

PubMed2007

Identification of specific protein markers in microdissected hepatocellular carcinoma.

At present, the molecular mechanisms of hepatocellular carcinogenesis are not well-understood, and hepatocellular carcinoma (HCC) stays one of the most frequent and high-risk metastatic visceral neoplasms worldwide. For the identification of tumor-relevant proteins, we analyzed microdissected cells from nontumorous liver tissue (n = 28) and tissue derived from hepatic tumor center (n = 25), as well as tumor margin (n = 23). We unequivocally identified 53 proteins from hepatic tumor tissues by peptide fingerprint mapping and SELDI mass spectrometry that were separated using two-dimensional gel electrophoresis. Among a number of signals that were detected as significantly different in the protein profiling analysis, we identified for the first time ferritin light subunit (FLS) and adenylate kinase 3 alpha-like 1 (AK3), showing decreased expressions in hepatic tumor, as well as biliverdin reductase B (BVRB) that was upregulated in HCC. The use of ProteinChip technology in combination with tissue microdissection gives insight of the complex changes occurring at the protein level in hepatocellular cancer associated with tumor development and progression and resulted in three new potential diagnostically useful markers.

Biomarkers↗

PubMed2006

Corazonin in insects.

Corazonin is a peptidergic neurohormone of insects that is expressed in neurosecretory neurons of the pars lateralis of the protocerebrum and transported via nervi corporis cardiaci to the storage lobes of the corpora cardiaca. This peptide occurs with a single isoform in all insects studied so far, with the exception of the Coleoptera in which no corazonin form could be detected. Very few modifications of [Arg(7)]-corazonin, originally isolated from cockroaches, are known, namely [His(7)]-corazonin which is expressed in certain locusts and the stick insect Carausius morosus, and [Thr(4), His(7)]-corazonin recently described from the honey bee Apis mellifera. In this study, we performed a comprehensive screening for corazonin in the different insect groups after detecting of a fourth isoform in a crane fly, Tipula sp. ([Gln(10)]-corazonin). [Arg(7)]-corazonin is distributed in most major lineages of insects, and is thus the ancient form which was present at the time the phylum Insecta evolved. The replacement of Arg with His at position 7 from the N-terminus occurred several times in the evolution of insects. The third isoform, [Thr(4), His(7)]-corazonin, seems to be restricted to bees (Apidae); whereas wasps (Vespidae) and a bumble bee (Apidae) express other corazonins, specifically [His(7)]-corazonin and [Tyr(3), Gln(7), Gln(10)]-corazonin, respectively. A novel corazonin form, [His(4), Gln(7)]-corazonin, was also detected in all South African members of the newly described insect order Mantophasmatodea. The [His(4), Gln(7)]-corazonin separates these species from the Namibian Mantophasmatodea which express [Arg(7)]-corazonin and can be used as a distinct character to distinguish these morphologically similar insects.

Amino Acid Sequence↗

PubMed2006

A nonribosomal peptide synthetase (Pes1) confers protection against oxidative stress in Aspergillus fumigatus.

Aspergillus fumigatus is an important human fungal pathogen. The Aspergillus fumigatus genome contains 14 nonribosomal peptide synthetase genes, potentially responsible for generating metabolites that contribute to organismal virulence. Differential expression of the nonribosomal peptide synthetase gene, pes1, in four strains of Aspergillus fumigatus was observed. The pattern of pes1 expression differed from that of a putative siderophore synthetase gene, sidD, and so is unlikely to be involved in iron acquisition. The Pes1 protein (expected molecular mass 698 kDa) was partially purified and identified by immunoreactivity, peptide mass fingerprinting (36% sequence coverage) and MALDI LIFT-TOF/TOF MS (four internal peptides sequenced). A pes1 disruption mutant (delta pes1) of Aspergillus fumigatus strain 293.1 was generated and confirmed by Southern and western analysis, in addition to RT-PCR. The delta pes1 mutant also showed significantly reduced virulence in the Galleria mellonella model system (P < 0.001) and increased sensitivity to oxidative stress (P = 0.002) in culture and during neutrophil-mediated phagocytosis. In addition, the mutant exhibited altered conidial surface morphology and hydrophilicity, compared to Aspergillus fumigatus 293.1. It is concluded that pes1 contributes to improved fungal tolerance against oxidative stress, mediated by the conidial phenotype, during the infection process.

Aspergillus fumigatus↗

PubMed2005

Optimisation of a 2-D gel electrophoresis protocol for the human-pathogenic fungus Aspergillus fumigatus.

Aspergillus fumigatus is the most important airborne fungal pathogen causing life-threatening infections in immunosuppressed patients. One of the important questions concerning A. fumigatus is the identification of pathogenicity determinants. To obtain a comprehensive overview about the proteins produced at different physiological conditions that are related to the infectious process a proteomic approach has been applied. Here, 2-D gel electrophoresis for filamentous fungi was optimised concerning removal of interfering compounds, protein extraction and separation methods. A trichloroacetic acid-based precipitation method of proteins with their subsequent solubilisation by the use of a combination of CHAPS with a second sulfobetaine detergent gave the best results. The optimised protocol was evaluated by the analysis of the proteomes of A. fumigatus grown on two different carbon sources, i.e., glucose and ethanol. Carbon catabolite repression has not been studied in detail at the protein level in A. fumigatus yet. In addition, growth on ethanol leads to activation of the glyoxylate cycle which was shown to be essential for pathogenesis in bacteria and fungi. In A. fumigatus, differential patterns of enzymes of the gluconeogenesis, glyoxylate cycle and ethanol degradation pathway during growth on glucose and ethanol were observed.

Aspergillus fumigatus↗