Disease relevance of Lpo

• Following lactoperoxidase radioiodination of cell surfaces, it was found that the proportion of labeled macromolecules released by human melanoma cells in 3 hr (60.0 +/- 9.9% (S.D.)] did not differ significantly from that released in the same time by normal allogeneic keratinocytes (56.0 +/- 10.0%) or fibroblasts (42.1 +/- 11.1%) [1].
• Immunotoxins containing glucose oxidase and lactoperoxidase with tumoricidal properties: in vitro killing effectiveness in a mouse plasmacytoma cell model [2].
• Line 1 carcinoma cells derived from a spontaneous alveolar carcinoma of BALB/c mice were labeled externally with 125I by use of lactoperoxidase or metabolically with [3H]-leucine before cell proteins were solubilized with Triton X-100 detergent [3].
• This E2-species could not be detected on the surface of mouse hepatitis virus A59-infected cells with indirect immunofluorescence staining or lactoperoxidase labeling [4].
• B2C11 immunoprecipitation of detergent-solubilized membrane proteins from both lactoperoxidase iodinated C6 and PC12 rat pheochromocytoma cells indicated a single band with an apparent molecular weight of 21,000-23,000 [5].

High impact information on Lpo

• This suggested that cytotoxicity was not dependent upon myeloperoxidase, and that lactoperoxidase may have diverted H2O2 from the oxidation of target cells to oxidation of substances in serum [6].
• Neither azide nor cyanide reduced cytolysis, but there was marked inhibition by lactoperoxidase and iodide [6].
• Examination of the labeled molecules precipitated from detergent extracts of spleen cells and thymocytes iodinated by the lactoperoxidase technique by SDS-PAGE confirm that there are structural differences between the antigens found on B and T lymphocytes [7].
• Specific anti-Ly sera were employed to precipitate Ly antigens from Nonidet P-40 extracts of mouse thymocytes labeled with 125I using lactoperoxidase and with NaB3H4 using galactose oxidase [8].
• Lymphoid cells from strain 2 and strain 13 guinea pigs were surface labeled with 125I by the lactoperoxidase technique [9].

Chemical compound and disease context of Lpo

• Membrane proteins from the B lymphomas WEHI-231 and 2PK3 and from the plasmacytomas MPC-11 and MOPC-21 were radioiodinated in situ by the lactoperoxidase method and were subjected to two-dimensional (nonreduced, reduced) polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate [10].
• 0. From these findings, we concluded that the exposure of B-16 melanoma cells to a system consisting of myeloperoxidase, hydrogen peroxide (generated by the glucose+glucose oxidase system) and chloride or bromide, or of lactoperoxidase, the hydrogen peroxide and bromide, at moderately acidic pH, causes cytolysis is accompanied by cell death [11].
• Surface proteins from five cell lines (three embryonal carcinoma cell lines (F9, PCC4 and PCC3), teratocarcinoma-derived endodermal cells (PYS) and fibroblasts (line 3/A/1-D-3 differentiated from PCC3) were compared by two-dimensional polyacrylamide gel electrophoresis after selective iodination with 125I in the presence of lactoperoxidase [12].

Biological context of Lpo

• We describe a method for the specific radioiodination of pinocytic vesicles (PVs) based upon the simultaneous endocytosis of lactoperoxidase (LPO) and glucose oxidase (GO) [13].
• Iodination of cells in suspension results in lactoperoxidase-specific iodide incorporation with no loss of cell viability under the conditions employed, less than 3% lipid labeling, and more than 90% of the labeled species identifiable as monoiodotyrosine [14].
• Initial experiments indicated that LPO was interiorized by the macrophage cell line J774 by fluid phase pinocytosis and without detectable binding to the plasma membrane (PM) [13].
• This molecule was a major surface constituent of myeloid cells with 10(6) antibody binding sites per cell containing 10% of total 125I incorporated by the lactoperoxidase procedure [15].
• These results indicate that upon binding fatty acid, 422(aP2) protein undergoes a conformational change whereby Tyr19, which lies within a consensus-type sequence for tyrosine kinase substrates, becomes accessible for phosphorylation by the insulin receptor tyrosine kinase and to iodination by lactoperoxidase [16].

Anatomical context of Lpo

• It is possible that the marked degree of exposure of the 50,000 mol wt polypeptide to immobilized LPO is related to the unique strength of macrophages attachment [17].
• These organelles rapidly fuse with preexisting lysosomes and are converted to phagolysosomes (PL) that demonstrates both acid phosphatase and lactoperoxidase activities [18].
• LPO was iodinated only after PV labeling and was present within organelles demonstrating latency [13].
• The 55,000 mol wt polypeptide can also be identified in Triton X-100 cytoskeletons from L929 cells after labeling with soluble LPO either before or after detergent lysis [17].
• The gel patterns of iodinated proteins showed specific differences in the availability of membrane proteins to lactoperoxidase labeling between inside-out and right-side-out membranes [19].

Associations of Lpo with chemical compounds

• After labeling of both L929 cells and macrophages with immobilized LPO, all polypeptides in this molecular weight region were subjected to peptide mapping by simultaneous limited proteolysis and electrophoresis in a second SDS polyacrylamide slab gel [17].
• Use of immobilized lactoperoxidase to label L cell proteins involved in adhesion to polystyrene [20].
• Lactoperoxidase beads were used to selectively label the apical surfaces of confluent endothelial monolayers, the total surfaces of nonenzymatically resuspended cells, and the basal surfaces of monolayers inverted on poly-L-lysine-coated coverslips, while maintaining greater than 98% viability in all samples [21].
• Platelet LFA-1, as demonstrated by surface iodination with lactoperoxidase and by labeling sialic acid residues with sodium borohydride, was not a major component of the platelet membrane [22].
• Similarly, tunicamycin prevents the appearance of membrane-associated viral antigens that can be labeled externally by lactoperoxidase-mediated iodination and it protects the cells against the cytolytic effects of MTV-specific antiserum and complement [23].

Other interactions of Lpo

• Experiments with specific antisera show that TSP-180 is not lactoperoxidase, fetal bovine serum protein, large external transformation-sensitive protein, or an antigen related to murine leukemia virus proteins [24].
• These proteins were also radiolabeled by lactoperoxidase catalyzed iodination and were sensitive to mild tryptic digestion, suggesting that they localized on the cell surface or in the extracellular matrix [25].
• The superpotent and enzymatically resistant alpha MSH analog, Nle4,D-Phe7-alpha MSH (NDP-MSH), was radioiodinated using lactoperoxidase (Enzymobeads) and purified by reverse phase chromatography for use as a tracer [26].
• Iodination by fungi with lactoperoxidase was reduced when blastoconidia were incubated at 25 degrees C or in the presence of catalase and the metabolic inhibitors rotenone, antimycin A, and 2-deoxyglucose [27].
• Lactoperoxidase iodination of cell surface proteins showed the appearance of an Mr 86,000 protein in the tumorigenic and metastatic cell variants [28].

Analytical, diagnostic and therapeutic context of Lpo

• 125I-Labeled membrane glycoproteins that specifically interact with diphtheria toxin and CRM197 protein--but not with diphtheria toxoid, fragment A of diphtheria toxin, or cholera toxin--were detected by use of the lactoperoxidase labeling technique followed by an immunoprecipitation system [29].
• Proteins from 131I/lactoperoxidase-labeled phagolysosomes, phagolysosomes derived from 131I/lactoperoxidase-labeled cells, and phagolysosomes prepared from [35S]methionine metabolically labeled cells were analyzed by high-resolution two-dimensional gel electrophoresis [19].
• Cell-surface vascular proteins were radiolabeled in situ via intracardiac perfusion with lactoperoxidase/Na125I [30].
• Tissue-culture cell fractionation. Fractionation of cellular membranes from 125I/lactoperoxidase-labelled Lettrée cells homogenized by bicarbonate-induced lysis: resolution of membranes by zonal centrifugation and in sucrose and metrizamide gradients [31].
• Lactoperoxidase-mediated iodination at 4 degrees C--an established method for covalent labelling of plasma membrane proteins--and quantitative electron microscopic autoradiography were used to follow the pathways of endocytosis in mouse macrophages in vitro [32].

References