scholarly journals Guanine-nucleotide-binding proteins expressed in rat white adipose tissue. Identification of both mRNAs and proteins corresponding to Gi1, Gi2 and Gi3

1989 ◽  
Vol 262 (2) ◽  
pp. 403-408 ◽  
Author(s):  
F M Mitchell ◽  
S L Griffiths ◽  
E D Saggerson ◽  
M D Houslay ◽  
J T Knowler ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Binding Proteins ◽  
Nucleotide Binding ◽  
Guanine Nucleotide ◽  
Alpha Subunits ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Proteins ◽  
Guanine Nucleotide Binding Proteins

Considerable debate has focused on the molecular identity of the guanine-nucleotide-binding proteins (G-proteins) in adipose tissue which can be detected following pertussis-toxin-catalysed ADP-ribosylation [Rapiejko, Northup, Evans, Brown & Malbon (1986) Biochem. J. 240, 35-40; Hinsch, Rosenthal, Spicher, Binder, Gausepohl, Frank, Schultz & Joost (1988) FEBS Lett. 238, 191-196]. We have used a panel of selective anti-peptide antisera which are able to discriminate between the different pertussis-toxin-sensitive G-proteins to assess which of these are expressed in rat adipose tissue. We demonstrate that plasma membranes of rat white adipocytes contain alpha subunits corresponding to each of Gi1, Gi2 and Gi3. Furthermore, using synthetic oligonucleotides complimentary to unique regions of each of the three polypeptides, we demonstrate that the mRNAs for the three G-protein alpha subunits can also be detected in adipose tissue.

scholarly journals Activation of superoxide formation and lysozyme release in human neutrophils by the synthetic lipopeptide Pam3Cys-Ser-(Lys)4. Involvement of guanine-nucleotide-binding proteins and synergism with chemotactic peptides

1990 ◽  
Vol 267 (3) ◽  
pp. 795-802 ◽  
Author(s):  
R Seifert ◽  
G Schultz ◽  
M Richter-Freund ◽  
J Metzger ◽  
K H Wiesmüller ◽  
...  
Keyword(s):  
G Proteins ◽  
Pertussis Toxin ◽  
Binding Proteins ◽  
Human Neutrophils ◽  
Guanine Nucleotide ◽  
Chemotactic Peptide ◽  
Chemotactic Peptides ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Proteins ◽  
Guanine Nucleotide Binding Proteins

Upon exposure to the bacterial chemotactic peptide fMet-Leu-Phe, human neutrophils release lysozyme and generate superoxide anions (O2.-). The synthetic lipoamino acid N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-(R)-cysteine (Pam3Cys), which is derived from the N-terminus of bacterial lipoprotein, when attached to Ser-(Lys)4 [giving Pam3Cys-Ser-(Lys)4], activated O2.- formation and lysozyme release in human neutrophils with an effectiveness amounting to about 15% of that of fMet-Leu-Phe. Palmitic acid, muramyl dipeptide, lipopolysaccharide and the lipopeptides Pam3Cys-Ala-Gly, Pam3Cys-Ser-Gly, Pam3Cys-Ser, Pam3Cys-OMe and Pam3Cys-OH did not activate O2.- formation. Pertussis toxin, which ADP-ribosylates guanine-nucleotide-binding proteins (G-proteins) and functionally uncouples formyl peptide receptors from G-proteins, prevented activation of O2.- formation by fMet-Leu-Phe and inhibited Pam3Cys-Ser-(Lys)4-induced O2.- formation by 85%. Lipopeptide-induced exocytosis was pertussis-toxin-insensitive. O2.- formation induced by Pam3Cys-Ser-(Lys)4 and fMet-Leu-Phe was enhanced by cytochalasin B, by a phorbol ester and by a diacylglycerol kinase inhibitor. Addition of activators of adenylate cyclase and removal of extracellular Ca2+ inhibited O2.- formation by fMet-Leu-Phe and Pam3Cys-Ser-(Lys)4 to different extents. Pam3Cys-Ser-(Lys)4 synergistically enhanced fMet-Leu-Phe-induced O2.- formation and primed neutrophils to respond to the chemotactic peptide at non-stimulatory concentrations. Our data suggest the following. (1) Pam3Cys-Ser-(Lys)4 activates neutrophils through G-proteins, involving pertussis-toxin-sensitive and -insensitive processes. (2) The signal transduction pathways activated by fMet-Leu-Phe and Pam3Cys-Ser-(Lys)4 are similar but not identical. (3) In inflammatory processes, bacterial lipoproteins and chemotactic peptides may interact synergistically to activate O2.- formation, leading to enhanced bactericidal activity.

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