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Biomedical subjects

H L Malech

Publications and source records attributed to H L Malech.

At least 109 records · Page 6Linked to original sources
PubMed1989

Regulation of immunoglobulin production in hyperimmunoglobulin E recurrent-infection syndrome by interferon gamma.

The hyperimmunoglobulin E recurrent-infection (Job) syndrome (HIE) is a congenital disorder characterized by high serum IgE, chronic eczematoid dermatitis, and recurrent infections. We examined the effect of interferon gamma (IFN-gamma) on excessive IgE production in HIE patients. Spontaneous in vitro production of IgE by peripheral blood mononuclear cells from HIE patients was elevated compared to normal individuals and correlated with serum IgE. In 9 of 13 patients, IgE production by peripheral blood mononuclear cells was inhibited by 50% by IFN-gamma at 100-1000 units/ml, whereas inhibition by IFN-gamma at 10(4) units/ml ranged from 67 to 93% for these 9 patients. IFN-gamma also inhibited IgG1, IgG3, and IgG4 production by B lymphocytes without inhibiting IgG2 production. IFN-gamma was administered subcutaneously to 5 HIE patients. After 2 weeks of treatment with IFN-gamma (0.05 mg/m2) at three doses per week given on alternate days, peripheral blood mononuclear cells from all 5 HIE patients decreased spontaneous in vitro IgE production (27-62% decrease) with no change in IgG and IgM. One patient had a 58% decrease in serum IgE and another patient had a 50% decrease in serum IgE after the IFN-gamma was increased to 0.1 mg/m2 for three doses per week for a month. In both patients, serum IgE returned to pre-IFN-gamma-challenge levels 1-3 months after completion of treatment, and in vivo IFN-gamma did not affect serum IgG and IgM, although serum IgG4 decreased with changes in serum IgE. Our studies demonstrate that IFN-gamma can regulate production of IgE and some IgG subclasses in humans.

Antibody Formation↗
PubMed1989

Selective defect in myeloid cell lactoferrin gene expression in neutrophil specific granule deficiency.

Neutrophil specific granule deficiency (SGD) is a congenital disorder associated with an impaired inflammatory response and a deficiency of several granule proteins. The underlying abnormality causing the deficiencies is unknown. We examined mRNA transcription and protein synthesis of two neutrophil granule proteins, lactoferrin and myeloperoxidase in SGD. Metabolically labeled SGD nucleated marrow cells produced normal amounts of myeloperoxidase, but there was no detectable synthesis of lactoferrin. Transcripts of the expected size for lactoferrin were detectable in the nucleated marrow cells of two SGD patients, but were markedly diminished in abundance when compared with normal nucleated marrow cell RNA. Because lactoferrin is secreted by the glandular epithelia of several tissues, we also assessed lactoferrin in the nasal secretions of one SGD patient by ELISA and immunoblotting. Nasal secretory lactoferrin was the same molecular weight as neutrophil lactoferrin and was secreted in normal amounts. From these data, we conclude that lactoferrin deficiency in SGD neutrophils is tissue specific and is secondary to an abnormality of RNA production. We speculate that the deficiency of several granule proteins is due to a common defect in regulation of transcription that is responsible for the abnormal myeloid differentiation seen in SGD patients.

Blotting, Northern↗
PubMed1988

Two forms of autosomal chronic granulomatous disease lack distinct neutrophil cytosol factors.

Chronic granulomatous diseases of childhood (CGD) are a group of disorders of phagocytic cell superoxide (O2.-) production (respiratory burst). Anion exchange chromatography separated from normal neutrophil cytosol a 47-kilodalton neutrophil cytosol factor, NCF-1, that restored activity to defective neutrophil cytosol from most patients with autosomally inherited CGD in a cell-free O2.--generating system. A 65-kilodalton factor, NCF-2, restored activity to defective neutrophil cytosol from one patient with autosomal CGD. NCF-1, NCF-2, and a third cytosol fraction, NCF-3, were inactive alone or in pairs, but together replaced unfractionated cytosol in cell-free O2.- generation. Neutrophils deficient in NCF-1, but not NCF-2, did not phosphorylate the 47-kilodalton protein. It is proposed that NCF-1, NCF-2, and NCF-3 are essential for generation of O2.- by phagocytic cells and that genetic abnormalities of these cytosol components can result in the CGD phenotype.

Blotting, Western↗
PubMed1988

Hydroxyl radical production by stimulated neutrophils reappraised.

Release of active oxygen species during the human neutrophil respiratory burst is thought to be mandatory for effective defense against bacterial infections and may play an important role in damage to host tissues. Part of the critical bacterial and host tissue damage has been attributed to hydroxyl radicals produced from superoxide and hydrogen peroxide. Because of the short life time of the very reactive hydroxyl radical, direct study of hydroxyl radical production is not possible; therefore, indirect detection methods such as electron spin resonance (ESR) coupled with appropriate spin-trapping agents such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) have been used. Superoxide production during the oxidative burst has been unambiguously demonstrated. Recent reports claim that hydroxyl radicals are not made during neutrophil stimulation and offer as an explanation the presence of granular components that interfere with hydroxyl radical production. When using the spin-trap agent DMPO, absence of the relatively long-lived adducts DMPO-OH and DMPO-CH3 has been assumed to be prima facie evidence for lack of hydroxyl radical participation. We show that high superoxide flux produced during stimulation of human neutrophils rapidly destroys both DMPO-OH and DMPO-CH3. In accord with previous implications, our results provide an alternative explanation for the absence of .OH adduct in spin-trapping studies and corroborate results obtained using other methods that implicate hydroxyl radical production during neutrophil stimulation.

Cyclic N-Oxides↗
PubMed1988

Subcellular localization of Gi alpha in human neutrophils.

Subcellular fractions were prepared from human neutrophils by sucrose density gradient centrifugation and analyzed for Gi-like proteins by pertussis toxin-catalyzed [32P]ADP-ribosylation and by immunoblotting with rabbit antiserum AS/6 which recognizes purified transducin and Gi, but not Gs or Go alpha-subunits. In resting cells, approximately equal to 60% of pertussis toxin substrate retrieved from the sucrose density gradient localized to the plasma membrane-enriched fraction, approximately equal to 35% to the specific granule-enriched fraction, and approximately equal to 5% to cytosol. The azurophil granule-enriched fraction did not contain pertussis toxin substrate. In contrast to plasma membrane, the specific granule-enriched fraction demonstrated increased AS/6 immunoreactivity of a approximately equal to 41-kDa protein relative to a approximately equal to 40-kDa protein. Within the specific granule-enriched fraction, the peak of pertussis toxin substrate detected immunochemically or by [32P]ADP-ribosylation sedimented at a lighter density (rho = 1.6 g/ml) than did lactoferrin (rho = 1.19 g/ml), suggesting that the intracellular compartment bearing pertussis toxin substrate may not be the lactoferrin containing specific granule, per se. Furthermore, in neutrophils exposed to 10(-8) M N-formylmethionylleucylphenylalanine, a weak degranulating stimulus (7% lactoferrin degranulation), there was a 31-42% decline in pertussus toxin-catalyzed [32P]ADP-ribosylation of approximately equal to 40-41-kDa proteins in the specific granule-enriched fraction accompanied by a near-quantitative increase in labeling of plasma membrane. The pool of intracellular formyl peptide receptors localized to the specific granule-enriched fraction appeared functionally coupled to a cosedimenting G-protein in experiments demonstrating modulation of high affinity N-formylmethionylleucyl[3H]phenylalanine binding by guanosine 5'-(3-O-thio)triphosphate or pertussis toxin. The data indicate that neutrophils contain a surface translocatable pool of intracellular G-protein sedimenting in the specific granule-enriched fraction and support the view that mobilization of intracellular G-protein represents a mechanism by which cells can regulate receptor activity.

Adenosine Diphosphate Ribose↗
PubMed1988

Recombinant human interferon-gamma reconstitutes defective phagocyte function in patients with chronic granulomatous disease of childhood.

Monocytes from 19 of 30 patients with the classic phenotype of chronic granulomatous disease of childhood (CGD) responded to 3 days of treatment in culture with recombinant human interferon-gamma (rHuIFN-gamma) at 100 units/ml by producing superoxide after stimulation with phorbol 12-myristate 13-acetate. Cells from 15 of 16 patients with cytochrome b-positive CGD (15 with autosomal and 1 with X chromosome-linked inheritance) and cells from 4 of 14 patients with cytochrome b-negative CGD (13 with X chromosome-linked and 1 with autosomal recessive inheritance) responded. Subcutaneous rHuIFN-gamma (0.01-0.05 mg/m2) administered as a single dose, daily or every other day, for five or six doses to 3 patients whose phagocytes responded to rHuIFN-gamma in vitro resulted in significant improvement in phagocyte bactericidal activity against Staphylococcus aureus and increases in superoxide production. Studies on 1 patient's cells indicated the increases in superoxide production correlated with increased membrane cytochrome b. The effects of rHuIFN-gamma persisted for more than a week following cessation of therapy. Thus, we have demonstrated a partial correction in vivo of these CGD patients' phagocyte defect with rHuIFN-gamma. Moreover, the data suggest that a significant proportion of patients with CGD will respond to rHuIFN-gamma with augmentation of phagocyte microbicidal function.

Blood Bactericidal Activity↗
PubMed1988

Stimulation of superoxide and lactoferrin release from polymorphonuclear leukocytes by the type 2 fimbrial lectin of Actinomyces viscosus T14V.

Polymorphonuclear leukocyte (PMN)-dependent destruction of Actinomyces viscosus T14V is initiated by the recognition of galactose-containing receptors on sialidase-treated PMNs by the lectin associated with the type 2 fimbriae of these bacteria. A. viscosus T14V also stimulates the respiratory burst in PMNs as well as the release of contents of the secondary granules, as determined by the presence of lactoferrin in the culture supernatants. Under the experimental conditions employed, these bacteria do not induce the release of beta-glucuronidase, a constituent of primary granules. None of the three PMN responses studied occurs in cultures containing a mutant of A. viscosus T14V that lacks fimbriae. Activation of the PMNs is mediated by the lectin associated with the type 2 fimbriae, as demonstrated by the finding that beta-linked galactosides inhibit stimulation of the respiratory burst. Thus, the interaction of the Actinomyces fimbrial lectin with its complementary receptors on PMNs results not only in killing of these bacteria but also in the release of reactive oxygen intermediates and enzymes that may be detrimental to surrounding host tissues.

Actinomyces↗
PubMed1987

Formyl peptide leukocyte chemoattractant uptake and release by cultured human umbilical vein endothelial cells.

Recent observations support an active role for the vascular endothelial cell in the induction and evolution of the inflammatory response. Since prior studies suggested that cultured bovine endothelial cells express high affinity binding sites for the neutrophil chemotactic oligopeptide formyl methionyl-leucyl-phenylalanine (f-Met-Leu-Phe), we sought to further characterize the interaction between formyl peptide chemoattractants and human vascular endothelial cells. Cultured human umbilical vein endothelial cells and peripheral blood neutrophils specifically bound f-Met-Leu-[3H]Phe, whereas specific binding to cultured fibroblasts, smooth muscle, and epithelial cells was negligible. Endothelial cells expressed 3.6 +/- 0.7 X 10(5) binding sites/cell with a Kd of 210 +/- 31 nM. Although the hexapeptide formyl norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-lysine (f-Nle-Leu-Phe-Nle-Tyr-Lys) and the tetrapeptide f-Met-Leu-Phe-Lys completed with f-Met-Leu-[3H]Phe for binding to endothelial cells, specific binding of 125I-f-Nl-Leu-Phe-Tyr-Lys or f-Met-Leu-Phe-Lys-fluorescein to endothelial cells was not observed, suggesting that steric constraints on formyl peptide binding differ between endothelial cells and leukocytes. At 37 degrees C, cell-associated f-Met-Leu-[3H]Phe greatly exceeded that bound at 0 degrees C and was incorporated predominantly into a nondisplaceable compartment. Release of f-Met-Leu-[3H]Phe or radioactive breakdown products from this compartment was time- and temperature-dependent with a t1/2 of approximately equal to 20 min at 37 degrees C. Resolution of the radioactive products released from f-Met-Leu-[3H]Phe-loaded endothelial cells by thin layer chromatography indicated that greater than or equal to 57% of the released material co-migrated with intact f-Met-Leu-[3H]Phe. Degradative release was blocked by agents that interfere with lysosomal acidification. The radioactive material released from f-Met-Leu-[3H]Phe-loaded endothelial cells bound specifically to neutrophils. This binding was inhibited 50.2 +/- 6.4% by a greater than or equal to 10(3)-fold excess of nonradioactive f-Met-Leu-Phe whereas binding of authentic f-Met-Leu-[3H]Phe was inhibited 89.4 +/- 3.0%. Supernatant obtained from f-Met-Leu-[3H]Phe-loaded endothelial cells elicited a rise in neutrophil cytosolic free calcium ([Ca2+]i) measured by quin2 fluorescence. The change in neutrophil [Ca2+]i depended on ligand binding to the neutrophil formyl peptide receptor since endothelial supernatants were devoid of activity in the presence of the f-Met-Leu-Phe antagonist, tert-butoxycarbonyl-Phe-Leu-Phe-Leu-Phe.(ABSTRACT TRUNCATED AT 400 WORDS)

Cells, Cultured↗
PubMed1987

Antibodies directed against synthetic peptides distinguish between GTP-binding proteins in neutrophil and brain.

Antisera AS/6 and 7, raised against a synthetic peptide KENLKDCGLF corresponding to the carboxyl-terminal decapeptide of transducin-alpha, react on immunoblots with purified transducin-alpha and with proteins of 40-41 kDa in all tissues tested. The latter represent one or more forms of Gi alpha but not Go alpha, since a synthetic peptide, KNNLKDCGLF, corresponding to the carboxyl-terminal decapeptide of two forms of Gi alpha blocks AS/6 and 7 reactivity with transducin-alpha and Gi alpha on immunoblots, whereas the corresponding Go-related peptide, ANNLRGCGLY, does not. Antisera LE/2 and 3, raised against the synthetic peptide LERIAQSDYI, corresponding to an internal sequence predicted by one form of Gi alpha cDNA (Gi alpha-2) and differing by 3 residues from the sequence of another form, Gi alpha-1, react strongly with a 40-kDa protein abundant in neutrophil membranes and with the major pertussis toxin substrate purified from bovine neutrophils. LE/2 and 3 reveal a relatively faint 40-kDa band on immunoblots of crude brain membranes or of purified brain Gi/Go. LE/2 and 3 do not react with transducin-alpha or Go alpha nor with the 41-kDa form of pertussis toxin substrate in brain, Gi alpha-1. These antisera distinguish between the major pertussis toxin substrates of brain and neutrophil and tentatively identify the latter as Gi alpha-2.

Amino Acid Sequence↗
PubMed1987

Detection of multiple forms of Gi alpha in HL60 cells.

Comparison of cDNA sequences from multiple sources predicts a genus of highly homologous but structurally distinct G protein alpha-subunits, designated as Gi alpha, that may include the alpha-subunit of the functionally defined adenylate cyclase inhibitory G protein. Using specific oligonucleotide probes on Northern blots, we show that Gi alpha-2 and Gi alpha-3, but not Gi alpha-1, are expressed in HL60 cells. Antisera raised against synthetic peptides from regions predicted to be conserved (AS6) and divergent (LE3) among Gi alpha subtypes bind to a 40 kDa protein in Western blots of HL60 membranes. AS6 identifies an additional protein at 41 kDa. Thus, Northern blot and immunoblot results show that at least two Gi alpha subtypes, a 40 kDa protein likely to correspond to Gi alpha-2 and a 41 kDa protein possibly representing Gi alpha-3, may be expressed in a single cell type.

Amino Acid Sequence↗
PubMed1987

The effects of phorbol myristate acetate and chemotactic peptide on transmembrane potentials and cytosolic free calcium in mature granulocytes evolve sequentially as the cells differentiate.

We isolated myeloid precursors from human marrow and studied the effects of phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) upon transmembrane potentials and cytosolic calcium ([Ca2+]i) as the cells matured. Using a panel of fluorescent probes, we found that membrane depolarization induced by PMA and fMLP in granulocytes, and elevation in [Ca2+]i stimulated by fMLP, were absent in myeloblasts. When we induced differentiation with granulocyte-macrophage colony-stimulating factors, we found that both ionic responses appeared at approximately the promyelocyte stage. By using di-O-C5(3), we detected an initial phase of fMLP-induced hyperpolarization which appeared ontogenetically earlier than depolarization and which could be evoked in mature granulocytes with lower concentrations of the ligand. Hyperpolarization was partially dependent on extracellular Na+, was abrogated by increasing the external K+ concentration, and was accompanied by mild acidification of the cytoplasm. Bordetella pertussis toxin abolished both hyperpolarization and depolarization. Our findings indicate that shifts in [Ca2+]i and membrane potential changes in response to PMA and fMLP evolve as granulocytes mature. In addition, transmembrane ionic fluxes induced by fMLP appear to be more complex than previously considered, involving at least two separable phases of membrane potential change.

Aminoquinolines↗
PubMed1987

Host defense during pregnancy: neutrophil chemotaxis and adherence.

Pregnancy is associated with impairment in several immunologic functions that effect the outcome of certain infectious and autoimmune diseases. Previous studies have indicated that pregnant women have decreased neutrophil motility, but results are discordant. We performed a longitudinal study of polymorphonuclear leukocyte chemotaxis using a micropore filter assay and polymorphonuclear leukocyte adherence using a nylon wool column assay in 58 women during pregnancy, delivery, and the postpartum period. Polymorphonuclear leukocyte chemotaxis was decreased significantly in pregnant women during the second (-20%) and third (-17%) trimesters and 1 to 3 months post partum (-18%), but not during the first trimester (-6%) compared with nonpregnant control subjects. The impairment in polymorphonuclear leukocyte chemotaxis appeared to be a cell-associated rather than a humoral defect. Polymorphonuclear leukocyte adherence was decreased significantly in pregnant women during the third trimester (-16%). These data may help explain the increased incidence of infection and amelioration of certain immunologically mediated illnesses during pregnancy.

Cell Adhesion↗
PubMed1987

Loss of myeloid differentiation antigens precedes blastic transformation in chronic myelogenous leukemia.

In order to determine whether antigenic patterns alter with disease progression and are thereby suggestive of impending blast crisis in chronic myelogenous leukemia, 50 bone marrow biopsy specimens from 32 patients were examined retrospectively using indirect immunoperoxidase labeling with three monoclonal antibodies that detect myeloid antigens. Monoclonal antibodies PMN13F6, PMN7C3, and PMN8C7 detect human neutrophil antigens that first appear at the myeloblast, promyelocyte, and metamyelocyte stages of differentiation, respectively, and persist throughout later differentiation. Percentages of antigen-positive bone marrow cells during the chronic phase were compared with percentages of antigen-positive cells at blast transformation, and time from bone marrow biopsy until blast crisis was correlated with the percentage of bone marrow cells expressing these antigens. Bone marrow biopsy samples from patients in the chronic phase who continue to remain clinically stable 4 to 106 months after biopsy expressed PMN13F6 antigen on 82% +/- 9% (mean +/- SD) of cells, PMN7C3 antigen on 62% +/- 14% of cells, and PMN8C7 on 68% +/- 14% of cells. Bone marrow biopsy specimens obtained from patients 1 or more years prior to blast transformation expressed PMN13F6 antigen on 81% +/- 12%, PMN7C3 antigen on 71% +/- 16%, and PMN8C7 on 64% +/- 16% of cells. Bone marrow biopsy samples obtained between 2 months and 1 year prior to blast crisis expressed PMN13F6 antigen on 68% +/- 15%, PMN7C3 on 51% +/- 17%, and PMN8C7 antigen on 46% +/- 18% of cells. Bone marrow biopsy specimens taken at the time of blast transformation expressed PMN13F6 antigen on 20% +/- 25%, PMN7C3 antigen on 19% +/- 25%, and PMN8C7 antigen on 13% +/- 25% of cells. The difference between the mean of antigen-positive cells from bone marrow biopsy samples obtained at the time of blast crisis was significant compared with the mean of positive cells from biopsy specimens obtained at all other phases of the disease (P less than .001 for all three antibodies). There was a positive correlation between loss of myeloid antigens and disease progression as determined by simple regression of log time and correlation analysis (PMN13F6, r = .6533, P less than .005; PMN7C8, r = .6304, P less than .005; PMN8C7, r = .5215, P less than .05). There was a negative correlation between percentage of immature cells and time to blastic crisis (r = -.6206, P less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1987

Swainsonine induced modification of N-linked oligosaccharides on human phagocytic cell formyl peptide chemotactic receptors.

Swainsonine, a Golgi mannosidase II inhibitor, causes a 15,000 dalton decrease in the apparent molecular weight of formyl peptide chemotactic receptor (FPCR) synthesized by three types of human phagocytic cells (differentiated HL-60 cells, differentiated U-937 cells, and cultured human macrophages derived from peripheral blood monocytes). This indicates that some of the asparagine-linked (N-linked) oligosaccharide of FPCR is of the complex type. Studies with endoglycosidase F and endoglycosidase H show that unaltered FPCR contains both complex and high mannose content N-linked oligosaccharide chains, and that FPCR synthesized in the presence of swainsonine contains only high mannose N-linked oligosaccharide chains. Cycloheximide prevents the swainsonine effect on FPCR molecular weight. This shows that swainsonine only affects the carbohydrate structure of FPCR which is newly synthesized in the presence of swainsonine. Since swainsonine decreases the molecular weight of FPCR from human peripheral blood monocytes in culture, these cells must be synthesizing new FPCR. The abnormally low molecular weight FPCR synthesized in the presence of swainsonine is converted to the normal, higher molecular weight form of FPCR when swainsonine is removed from the culture. This occurs even when new protein synthesis is inhibited by cycloheximide. This requires that previously synthesized, swainsonine-affected FPCR at the cell surface must come in contact with Golgi enzymes which complete the processing of the abnormal, high mannose oligosaccharide. This implies a potential Golgi-related repair mechanism for altered or "damaged" cell surface receptors.

Alkaloids↗
PubMed1987

Acquisition of formyl peptide receptors during normal human myeloid differentiation.

By using a newly developed immune rosetting technique to isolate highly purified populations of myeloid precursor cells from normal human bone marrow and then inducing their differentiation with granulocyte and macrophage colony-stimulating factors (G/M-CSFs) in vitro, we studied the surface expression of chemotactic peptide receptors as the cells matured from the stage of the myeloblast to that of the mature, segmented neutrophil. We used ethylene glycol bis(succinimidyl succinate) to link N-formyl-Nle-Leu-Phe-Nle-[125I]iodo-Tyr-Lys to chemotactic peptide receptors on the surface of myeloid cells at sequential stages of maturation and then determined the density of receptor-radioligand complexes by autoradiography after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Specific, saturable formyl peptide receptors were not detectable at the level of the myeloblast but gradually emerged through progressive stages of neutrophil maturation. The specific receptors for formyl peptide that appeared during cellular maturation had a mol wt of 55 to 70 kiloDalton (kD), corresponding to those present on the surface of peripheral blood neutrophils, and binding of the radioligand was highly specific in that it was completely inhibited by a 1,000-fold excess of F-Met Leu Phe. These data correlate with and provide insight into our recent observation that F-Met Leu Phe-induced membrane depolarization and transient increases in cytosolic free calcium are gradually acquired as neutrophils mature. This report represents to our knowledge the first description of the maturational development of chemotactic peptide receptor expression in normal human myeloid cells.

Bone Marrow↗
PubMed1986

Effects of tunicamycin on the expression and function of formyl peptide chemotactic receptors of differentiated HL-60 cells.

We previously showed that formyl peptide chemotactic receptors (FPCR) of human phagocytic cells contain at least two asparagine-linked oligosaccharide chains located at the distal end of the receptor. The requirement of these N-linked oligosaccharide chains for expression and function of FPCR was investigated in HL-60 cells induced to differentiate by N6,O2-dibutyryladenosine 3',5'-monophosphate (Bt2cAMP) in the presence or absence of 5 micrograms/ml tunicamycin. Tunicamycin did not prevent the changes in morphology associated with Bt2cAMP-induced differentiation of HL-60 cells. Autoradiographic analysis after SDS-PAGE of FPCR affinity labeled with N-formyl-Nle-Leu-Phe-Nle-[125I]iodo-Tyr-Lys (formyl 125I-hexapeptide) and ethylene glycol bis(succinimidyl succinate) demonstrated that greater than 95% of FPCR expressed by tunicamycin-treated cells completely lacked N-linked oligosaccharide (Mr 32,000), and no fully glycosylated FPCR (Mr 62,000 to 85,000) was detectable. Scatchard analysis of formyl 125I-hexapeptide binding indicated the presence of two classes of binding sites for both control and tunicamycin-treated cells (control cells, 82,000 +/- 32,000 sites/cell with Kd 10.0 +/- 4.3 nM and 520,000 +/- 40,000 sites/cell with Kd 250 +/- 80 nM; tunicamycin-treated cells, 11,000 +/- 5000 sites/cell with Kd 3.0 +/- 1.9 nM and 470,000 +/- 70,000 sites/cell with Kd of 500 +/- 140 nM). Both control and tunicamycin-treated cells augmented superoxide anion release, exhibited a migratory response, and showed a transient rise in intracellular free Ca2+ upon stimulation with N-formyl-Nle-Leu-Phe. However, the responses of the tunicamycin-treated cells were less than that of the control cells. The present studies demonstrate that N-glycosylation of FPCR is not essential for cell surface expression or for several FPCR-mediated cell responses.

Calcium↗