ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01607.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: The effects of interleukin 4 (IL‐4) on human leukemic precursor B‐cell lines were investigated. Recombinant IL‐4 (rIL‐4) was added to three acute lymphoblastic leukemia‐derived pre B‐cell lines: Reh, Km3 and Nalm‐6. Our results show that rIL‐4 significantly decreases continuous proliferation of Reh and Km3 cells while Nalm‐6 cells have a limited response in this respect. This rIL‐4 effect is dose‐dependent and can be neutralized by anti‐IL‐4 monoclonal antibody (mAb). Furthermore, rIL‐4 down‐regulated IL‐3‐induced proliferation of Reh cells. Phenotypic analysis of rIL‐4‐treated cells points to significant induction of surface marker maturation of leukemic cells by this cytokine. Together, thesein vitrodata suggest that IL‐4: 1) inhibits the proliferation and 2) promotes the differentiation of

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01608.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: The human C5a anaphylatoxin is a cationic 74 amino‐acid long glycopeptide which derives from proteolysis of the fifth component of complement. It interacts with high affinity with a receptor that belongs to the G protein‐coupled receptor superfamily. Several studies have previously suggested that multiple contact points between C5a and the receptor are required to achieve high‐affinity interaction. However, at the receptor level little is known about the sites of interaction with C5a. We have investigated byin vitromutagenesis whether the N‐terminal extracellular sequence of the C5a receptor, which is rich in aspartic acid residues, could play some role in C5a binding. Conversion of Asp10into asparagine did not impair the level of expression at the plasma membrane, nor did it alter the affinity for C5a. However, we consistently observed a discrepancy between an apparent high level of surface expression and a weak capacity to bind C5a with high affinity, suggesting that many receptor molecules, although present on the cell surface, might be misfolded and unable to bind C5a. Replacement of Pro9by an isoleucine had little effect, if any, on either the affinity or the C5a‐binding capacity, whereas the conversion of Pro36into leucine dramatically reduced the expression of high‐affinity receptor at the cell surface. N‐glycosylation of human C5a receptor was found to be dispensable for the function

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01609.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: Signal transduction via receptors for N‐formylmethionyl peptide chemoattractants (FPR) on human neutrophils is a highly regulated process. It involves direct interaction of receptors with heterotrimeric G‐proteins and may be under the control of cytoskeletal elements. Evidence exists suggesting that the cytoskeleton and/or the membrane skeleton determines the distribution of FPR in the plane of the plasma membrane, thus controlling FPR accessibility to different proteins in functionally distinct membrane domains. In desensitized cells, FPR are restricted to domains which are depleted of G proteins but enriched in cytoskeletal proteins such as actin and fodrin. Thus, the G protein signal transduction partners of FPR become inaccessible to the agonist‐occupied receptor, preventing cell activation. We are investigating the molecular basis for the interaction of FPR with the membrane skeleton, and our results suggest that FPR, and possibly other receptors, may directly bind to cytoskeletal proteins such a

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01610.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: The signal transductional mechanisms regulating the activation of NADPH oxidase, the respiratory burst enzyme in phagocytic cells, are not completely understood. Receptors for most physiologic stimuli trigger the activation of various phospholipases, including phospholipases A2, C, and D. The lipid mediators formed (arachidonic acid, 1,2‐diacylglycerol, and phosphatidic acid) have been implicated as second messengers in the induction of the respiratory burst. In intact cells, we have correlated phospholipase D activation and the production of phosphatidic acid with the activation of NADPH oxidase, using the drug propranolol. Phosphatidic acid activated NADPH oxidase in a cell‐free system, but the level of activation was low. 1,2‐Diacylglycerol markedly enhanced NADPH oxidase activation by phosphatidic acid. The synergistic effect required the diacyl species, since mono‐ or tri‐acylglycerols were ineffective. Phosphatidic acid could be replaced by either lysophosphatidic acid or phosphatidylserine, but not by phosphatidylcholine, phosphatidylethanolamine, or phosphatidylinositol, suggesting specificity for an anionic phospholipid. Since other cell‐free activators of NADPH oxidase (arachidonic acid, sodium dodecyl sulfate) are also anionic amphiphiles, phosphatidic acid may directly interact with an enzyme component(s). The targets for phosphatidic acid and diacylglycerol in the cell‐free system are currently under investigation. These results emphasize the critical importance of phospholipases, particularly phospholipase D, in the regulation of the re

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01611.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01612.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: When confronted with invading microorganisms, neutrophils undergo a number of nearly synchronous reactions including the generation of microbicidal reactive oxygen intermediates by the NADPH oxidase. These reactions are accompanied by a slow depolarization, from resting values of – 60 mV to levels probably exceeding 0 mV. The depolarization is transient, indicating that a compensatory charge transport mechanism is activated. Activation of the oxidase system causes a massive burst of metabolic acid generation that would, if uncompensated, lower the intracellular pH of neutrophils by over 5 units, to lethal levels (pH = 2). Neutrophils must therefore possess particularly effective regulatory systems to avoid excessive cytosolic acidification. The recently described H+conductance of neutrophils may counteract both the acidification and the depolarization. Activation of the H+conductance occurs at depolarizing voltages and is promoted by cytosolic acidification, a combination that takes place during the respiratory burst. The NADPH oxidase of neutrophils is thus associated to an unusual, particularly efficient mechanism of H+export and charge compensation. The sequential activation of these two systems causes neutrophils to depolarize through the activation of an electron transport chain, and to repolarize through the activation of a H+conducta

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01613.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract: The mechanisms used by phagocytic leukocytes in the process of bacterial killing are regulated by GTP‐binding proteins of the Ras superfamily. In particular, the formation of toxic oxygen metabolites via the NADPH oxidase requires the action of both Rac and Rap1A proteins. Rac2 forms a third cytosolic component of the human neutrophil NADPH oxidase. Rac2 is active in its GTP‐bound form, and requires post‐translational processing (isoprenylation) in order to interact with regulatory proteins which stimulate the exchange of GTP for GDP. In the resting neutrophil, Rac is localized to the cytosol in the form of a complex with a GDP dissociation inhibitor (GDI) protein. Upon cell activation, this complex is disrupted to enable Rac to translocate to the active oxidase at the plasma membrane. The Rac‐GDI complex may be regulated by the release of specific lipids known to be generated during phagocyte a

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01614.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01615.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0902-4441    

DOI:10.1111/j.1600-0609.1993.tb01616.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY