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At least 37 records · Page 2Linked to original sources
PubMed1993

Characterization of glycoprotein II from bovine adrenal medullary chromaffin granules. Identification of components representing the secretory vesicle counterparts of the lysosomal-associated membrane glycoproteins (lamp-1 and lamp-2).

Glycoprotein II (GpII) is a heterogenous glycoprotein isolated from the membranes of bovine chromaffin granules in the adrenal medulla. When viewed by two-dimensional electrophoresis this glycoprotein consists of two components, upper (GpIIa) and lower (GpIIb), with a molecular mass of 80,000-100,000 daltons and a pI of 4.2-4.7. NH2-terminal sequence analysis of GpIIa and GpIIb revealed sequence similarity with lysosomal membrane glycoproteins (lamp-1 and lamp-2), which was supported by sequence data of peptides from trypsin and cyanogen bromide digestions. An oligonucleotide probe was used to isolate a cDNA clone encoding the nucleotide sequence of GpIIa. The predicted amino acid sequence of GpIIa shares a 72% identity with the human lamp-1 type protein, which belongs to a highly conserved group of lysosomal-associated membrane glycoproteins (lamp proteins), whose function is still unknown. The COOH-terminal region of GpIIa was identical to the COOH-terminal region of lamp proteins. This COOH-terminal determinant has been demonstrated to be essential for the intracellular targeting of lamp proteins to lysosomes. A synthetic peptide antisera to the COOH-terminal region of GpIIa was used to show that this region is present on purified chromaffin granules and not proteolytically processed. The sequence analysis of GpIIa and immunological data confirm GpII as the secretory granule counterpart of lamp proteins and raise some questions regarding intracellular targeting between lysosomes and secretory granules within the chromaffin cell.

Adrenal Medulla↗
PubMed1990

The polylactosaminoglycans of human lysosomal membrane glycoproteins lamp-1 and lamp-2. Localization on the peptide backbones.

Lysosome membrane glycoproteins, lamp-1 and lamp-2, have been shown to contain 18 and 16 N-glycans, some of which are modified by poly-N-acetyl-lactosamine. We have localized the polylactosaminoglycans to specific sites on lamp-1 and lamp-2 purified from human chronic myelogenous leukemia cells. Polylactosaminoglycan-containing glycopeptides, obtained by trypsin, pepsin, and V8 protease digestion of the glycoproteins, were isolated by Datura stramonium agglutinin affinity chromatography, gel filtration, and reverse phase high performance liquid chromatography. The poly-N-acetyllactosaminyl structures of isolated glycopeptides were confirmed by the susceptibility of their released oligosaccharides to endo-beta-galactosidase. Amino acid analysis and sequencing demonstrated that polylactosaminoglycans were located at Asn-34, Asn-93 and/or Asn-102, and Asn-195 and/or Asn-200 in lamp-1, and at Asn-4 and/or Asn-10, and Asn-279 in lamp-2. These results indicated that only certain glycosylation sites can be selectively modified by poly-N-acetyllactosamine, and those sites may confer the requirement by beta 1----3-N-acetylglucosaminyl transferase.

Amino Acid Sequence↗
PubMed1999

Asparagine-linked oligosaccharides protect Lamp-1 and Lamp-2 from intracellular proteolysis.

Lysosomes contain several integral membrane proteins (termed Lamps and Limps) that are extensively glycosylated with asparagine-linked oligosaccharides. It has been postulated that these glycans protect the underlying polypeptides from the proteolytic environment of the lysosome. Previous attempts to test this hypothesis have been inconclusive because they utilized approaches that prevent initial glycosylation and thereby impair protein folding. We have used endoglycosidase H to remove the Asn-linked glycans from fully folded lysosomal membrane proteins in living cells. Deglycosylation of Lamp-1 and Lamp-2 resulted in their rapid degradation, whereas Limp-2 was relatively stable in the lysosome in the absence of high mannose Asn-linked oligosaccharides. Depletion of Lamp-1 and Lamp-2 had no measurable effect on endosomal/lysosomal pH, osmotic stability, or density, and cell viability was maintained. Transport of endocytosed material to dense lysosomes was delayed in endoglycosidase H treated cells, but the rate of degradation of internalized bovine serum albumin was unchanged. These data provide direct evidence that Asn-linked oligosaccharides protect a subset of lysosomal membrane proteins from proteolytic digestion in intact cells.

Animals↗
PubMed1997

Efficacy and safety of stand-up irradiation cubicles with UVA metal-halide lamps (and a new filter) or UVA fluorescent lamps for photochemotherapy of psoriasis.

BACKGROUND: Metal-halide lamps (MHLs) and fluorescent lamps (FLs) are widely employed for PUVA therapy of psoriasis, but they have never been compared in a clinical trial. OBJECTIVE: We studied the irradiance, spectral power distribution, irradiation field and efficacy of two cabinets with standard FLs or MHLs with a new UVA filter. METHODS: The photophysical properties of the lamps were studied with a spectroradiometer. After phototesting, 22 patients with recurrent plaque type psoriasis were treated in a stand-up irradiation cubicle housing 27 standard FLs, and, at recurrence, in a cubicle with 15 MHLs. When indicated, lesions of the legs underwent supplementary exposures with small FL or MHL devices. RESULTS: MHLs had a greater emission in the longer UVA wavelengths than FIs. The MHL cubicle had a greater irradiance and a more uniform output along the vertical axis. Both cubicles were effective in a similar number of exposures. However, FLs were more phototoxic and lower cumulative UVA doses were administered although the total duration of exposures was longer. Eleven patients treated with FLs and 7 patients with MHLs required supplementary treatments of the legs. The number, cumulative UVA dose and total duration of these exposures were significantly greater with FLs. CONCLUSION: Cabinets with MHLs increase the number of patients treated in the same time period and reduce the number of patients needing supplementary treatments of the legs. Cumulative UVA doses are greater with MHLs, but their emission is prevalent in the less erythematogenic and carcinogenic longer UVA wavelengths.

Adolescent↗
PubMed1975

Development of high intensity narrow-band lamps and studies of the irradiation effect on human skin. Irradiation with high intensity lamps.

A compact light source has been developed. It consists of a high-pressure mercury lamp, a shutter, and water-cooled filters for selected wavelength regions. A mixing device permits simultaneous irradiation from two lamps of different wavelengths. The spectral distribution of the light for seven filter combinations and the construction of a power meter are also described. The application of the lamps to clinical investigations is illustrated by determination of minimal erythemal and blister doses, as well as pigmentation, for various groups of patients. The light intensities available are high enough to make pain threshold measurements possible in the UV and visible regions.

Adolescent↗
PubMed1980

Retinal light exposure from ophthalmoscopes, slit lamps, and overhead surgical lamps. An analysis of potential hazards.

The projected beam radiance of several common ophthalmologic instruments was measured, and potential hazard to the patient from light exposure was analyzed with reference to safety standards for coherent light. The indirect ophthalmoscopes tested appear to be "safe" under moderate voltage settings, provided exposure is reasonably brief. Slit-lamp biomicroscopy of the fundus, however, merits caution. It produces a three-times-higher retinal irradiance than the indirect ophthalmoscope. Overhead surgical lamps produce a retinal irradiance about one-third that of the indirect ophthalmoscope (for clear media and dilated pupil). This could be dangerous, since an operation may take long enough to exceed the maximal permissible exposure by several orders of magnitude. Major design changes are indicated for surgical illuminators to extend the "safe time" to the 40 to 60 min range.

Animals↗
PubMed1994

Concomitant increases in galectin-1 and its glycoconjugate ligands (carcinoembryonic antigen, lamp-1, and lamp-2) in cultured human colon carcinoma cells by sodium butyrate.

Galactoside-binding lectins (galectins) with molecular masses of about 14.5 kilodaltons (galectin-1) and 31 kilodaltons (galectin-3) have been found in a variety of normal and malignant cells and have been implicated in the regulation of cell growth, cell adhesion, and metastasis. The KM12 human colon carcinoma cell line was found to express only galectin-3. Because the levels of both galectins are developmentally regulated and can be modulated during the differentiation of several cultured tumor cell lines, we studied the ability of 11 differentiation-inducing agents to induce galectin-1 expression in the KM12 cells. Treatment of these cells with sodium butyrate, an established differentiation-inducing agent for colon carcinoma cells, resulted in the induction of galectin-1, which was detected by immunoblotting as well as by affinity chromatography. This effect was not seen with any of the 10 other differentiating agents: hexamethylene bisacetamide, dimethyl sulfoxide, dimethyl formamide, herbimycin A, mycophenolic acid, retinoic acid, difluoromethyl ornithine, dibutyryl cAMP, 8-chloro cAMP, and transforming growth factor beta 1. Galectin-1 induction by butyrate was observed in seven other human colon carcinoma cell lines. Further studies with the KM12 cells revealed that butyrate caused cell flattening, suppressed cell proliferation and colony formation in agarose, and increased the level of carcinoembryonic antigen, a marker of human colon carcinoma cell differentiation, within 48 h of treatment. The increase in galectin-1 level was dependent linearly on butyrate concentration (range, 1-4 mM). Galectin-1 mRNA expression was detected by Northern blotting as early as 6 h, and the protein was detected after 24 h of treatment initiation. The level of the constitutively expressed galectin-3 was also increased by butyrate but to a lesser extent than the level of galectin-1. Butyrate-induced galectin-1 was detected on the cell surface by immunoprecipitation from radioiodinated cell surface proteins as well as by indirect immunofluorescence labeling. Affinity-purified human galectin-1 was found to bind to purified polylactosamine-containing glycoproteins and to detergent-solubilized cellular proteins electroblotted onto nitrocellulose membranes. Affinity chromatography of [3H]glucosamine-labeled KM12 cell extracts on immobilized galectin-1 followed by immunoprecipitation from the lactose-eluted material demonstrated that lysosome-associated membrane glycoprotein-1, carcinoembryonic antigen, and nonspecific cross-reacting antigen are the major galectin-1-binding proteins in these cells. These results indicate that galectin-1 expression may be associated with the differentiation of KM12 cells and that several glycoproteins shown to be important in colon carcinoma adhesion and metastasis are capable of functioning as its endogenous ligands.

Animals↗