Spectral analysis of flow cytometric data: design of a special-purpose low-pass digital filter

Spectral decomposition of flow cytometric datafiles of arbitrary dimension reveal information of both the signal and the noise components that constitute the histograms. This spectral information is used to construct a low-pass digital filter, which removes the high-frequency noise from the actual data. It is shown that this procedure guarantees non-trivial smoothing of the flow cytometric data in accordance with the local experimental situation. As a consequence optimal reconstruction of the signal is possible, which facilitates unambiguous interpretation of the data files and mathematical estimation of the statistical parameters.     

Quantitative expression profiling of G-protein-coupled receptors (GPCRs) in metastatic melanoma: the constitutively active orphan GPCR GPR18 as novel drug target

G-protein-coupled receptors (GPCRs) have been implicated in the tumorigenesis and metastasis of human cancers and are considered amongst the most desirable targets for drug development. Utilizing a robust quantitative PCR array, we quantified expression of 94 human GPCRs, including 75 orphan GPCRs and 19 chemokine receptors, and 36 chemokine ligands, in 40 melanoma metastases from different individuals and benign nevi. Inter-metastatic site comparison revealed that orphan GPR174 and CCL28 are statistically significantly overexpressed in subcutaneous metastases, while P2RY5 is overexpressed in brain metastases. Comparison between metastases (all three metastatic sites) and benign nevi revealed that 16 genes, including six orphan receptors (GPR18, GPR34, GPR119, GPR160, GPR183 and P2RY10) and chemokine receptors CCR5, CXCR4, and CXCR6, were statistically significantly differentially expressed. Subsequent functional experiments in yeast and melanoma cells indicate that GPR18, the most abundantly overexpressed orphan GPCR in all melanoma metastases, is constitutively active and inhibits apoptosis, indicating an important role for GPR18 in tumor cell survival. GPR18 and five other orphan GPCRs with yet unknown biological function may be considered potential novel anticancer targets in metastatic melanoma.     

Cloning and characterization of dominant negative splice variants of the human histamine H4 receptor

The H(4)R (histamine H(4) receptor) is the latest identified member of the histamine receptor subfamily of GPCRs (G-protein-coupled receptors) with potential functional implications in inflammatory diseases and cancer. The H(4)R is primarily expressed in eosinophils and mast cells and has the highest homology with the H(3)R. The occurrence of at least twenty different hH(3)R (human H(3)R) isoforms led us to investigate the possible existence of H(4)R splice variants. In the present paper, we report on the cloning of the first two alternatively spliced H(4)R isoforms from CD34+ cord blood-cell-derived eosinophils and mast cells. These H(4)R splice variants are localized predominantly intracellularly when expressed recombinantly in mammalian cells. We failed to detect any ligand binding, H(4)R-ligand induced signalling or constitutive activity for these H(4)R splice variants. However, when co-expressed with full-length H(4)R [H(4)R((390)) (H(4)R isoform of 390 amino acids)], the H(4)R splice variants have a dominant negative effect on the surface expression of H(4)R((390)). We detected H(4)R((390))-H(4)R splice variant hetero-oligomers by employing both biochemical (immunoprecipitation and cell-surface labelling) and biophysical [time-resolved FRET (fluorescence resonance energy transfer)] techniques. mRNAs encoding the H(4)R splice variants were detected in various cell types and expressed at similar levels to the full-length H(4)R((390)) mRNA in, for example, pre-monocytes. We conclude that the H(4)R splice variants described here have a dominant negative effect on H(4)R((390)) functionality, as they are able to retain H(4)R((390)) intracellularly and inactivate a population of H(4)R((390)), presumably via hetero-oligomerization.     

Studies on the binding site of the galactose-specific agglutinin PA-IL from Pseudomonas aeruginosa

The binding properties of Pseudomonas aeruginosa agglutinin-I (PA-IL) with glycoproteins (gps) and polysaccharides were studied by both the biotin/avidin-mediated microtiter plate lectin-binding assay and the inhibition of agglutinin-glycan interaction with sugar ligands. Among 36 glycans tested for binding, PA-IL reacted best with two glycoproteins containing Galalpha1-->4Gal determinants and a human blood group ABO precursor equivalent gp, but this lectin reacted weakly or not at all with A and H active gps or sialylated gps. Among the mammalian disaccharides tested by the inhibition assay, the human blood group Pkactive Galalpha1-->4Gal, was the best. It was 7.4-fold less active than melibiose (Galalpha1-->6Glc). PA-IL has a preference for the alpha-anomer in decreasing order as follows: Galalpha1-->6 >Galalpha1-->4 >Galalpha1-->3. Of the monosaccharides studied, the phenylbeta derivatives of Gal were much better inhibitors than the methylbeta derivative, while only an insignificant difference was found between the Galalpha anomer of methyl- and p -NO2-phenyl derivatives. From these results, it can be concluded that the combining size of the agglutinin is as large as a disaccharide of the alpha-anomer of Gal at nonreducing end and most complementary to Galalpha1-->6Glc. As for the combining site of PA-IL toward the beta-anomer, the size is assumed to be less than that of Gal; carbon-6 in the pyranose form is essential, and hydrophobic interaction is important for binding.      

Comparative characterization of hyperglycemic neuropeptides from the lobster Homarus americanus

With the use of a two-step HPLC purification procedure, two sets of two isoforms of the crustacean hyperglycemic hormone (CHH) were isolated from sinus glands of the lobster Homarus americanus. Structural differences between the two groups of isoforms were found in their amino acid sequences, amino acid compositions and precise molecular weights. Using peptide mapping, the difference between the isoforms in each group was located within the first eight amino acids at the N-termini. The nature of this difference remained unclear as all four peptides had the same N-terminal amino acid sequence unto residue 19.     

Isolation and amino acid sequence of crustacean hyperglycemic hormone precursor-related peptides.

The crustacean hyperglycemic hormone (CHH) is synthesized as part of a larger preprohormone in which the sequence of CHH is N-terminally flanked by a peptide for which the name CPRP (CHH precursor-related peptide) is proposed. Both CHH and CPRP are present in the sinus gland, the neurohemal organ of neurosecretory cells located in the eyestalk of decapod crustaceans. This paper describes the isolation and sequence analysis of CPRPs isolated from sinus glands of the crab Carcinus maenas, the crayfish Orconectes limosus and the lobster Homarus americanus. The published sequence of "peptide H" isolated from the land crab, Cardisoma carnifex, has now been recognized as a CPRP in this species. Sequence comparison reveals a high level of identity for the N-terminal region (residues 1-13) between all four peptides, while identity in the C-terminal domain is high between lobster and crayfish CPRP on the one hand, and between both crab species on the other. Conserved N-terminal residues include a putative monobasic processing site at position 11, which suggests that CPRP may be a biosynthetic intermediate from which a potentially bioactive decapeptide can be derived.