Related Experiment Video

Updated: Aug 10, 2026

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy
10:40

Studying Interactions of Staphylococcus aureus with Neutrophils by Flow Cytometry and Time Lapse Microscopy

Published on: July 17, 2013

G protein activation and mediator release from human neutrophils and platelets after stimulation with sodium fluoride

C Brom1, J Brom, W König

  • 1Lehrstuhl für Medizinische Mikrobiologie und Immunologie, Ruhr-Universität Bochum, Germany.

Immunology
|July 1, 1991
PubMed

Insights

Sequential cell activation with formyl-methionyl-leucyl-phenylalanine (FMLP) or thrombin, followed by sodium fluoride (NaF), revealed distinct G protein signaling pathways in human neutrophils and platelets, impacting mediator release and cell function.

Area of Science:

  • Cellular Biology
  • Immunology
  • Biochemistry

Background:

  • G proteins are crucial signal transducers in cellular responses.
  • Investigating G protein involvement in human polymorphonuclear granulocytes (PMN) and platelets is essential for understanding immune and hemostatic functions.
  • Receptor-mediated stimuli like formyl-methionyl-leucyl-phenylalanine (FMLP) and thrombin activate specific signaling pathways in these cells.

Purpose of the Study:

  • To investigate the differential cellular responses of human PMN and platelets upon sequential stimulation with receptor agonists and sodium fluoride (NaF).
  • To explore the role of G protein activation, using [3H]guanylylimidodiphosphate ([3H]Gpp (NH) p) binding as a marker, in modulating mediator release and cell function.
  • To elucidate the diversity of G protein signaling mechanisms and their regulatory control in distinct human cell types.

Main Methods:

  • Human PMN and platelets were pre-activated with FMLP or thrombin, respectively, followed by incubation with NaF.
  • Cellular responses including PMN chemiluminescence, platelet aggregation, and lipid mediator generation (leukotriene B4, 12-hydroxy-eicosatetraenoic acid) were measured.
  • [3H]Gpp (NH) p binding to membrane fractions of stimulated cells was determined as an indicator of G protein activation.

Main Results:

  • FMLP-pre-stimulated PMN exhibited enhanced leukotriene generation, with a second chemiluminescence response observed after NaF addition.
  • Thrombin-pre-stimulated platelets showed sub-additive mediator generation and partial inhibition of aggregation upon NaF treatment.
  • Gpp (NH) p binding patterns in PMN correlated with leukotriene release, but no such correlation was found in platelets for Gpp (NH) p binding, aggregation, or 12-HETE generation.

Conclusions:

  • Sequential stimulation leads to distinct cellular responses in PMN and platelets, highlighting the heterogeneity of G protein signaling pathways.
  • The observed differences suggest diverse regulatory mechanisms controlling G protein activation and downstream signaling in different cell types.
  • This study underscores the complexity of cellular signal transduction and the specific roles of G proteins in immune and hemostatic processes.

More Related Videos

Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay11:49

Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay

Published on: July 28, 2014

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators07:41

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators

Published on: February 20, 2018

Related Concept Videos

G-protein Coupled Receptors01:21

G-protein Coupled Receptors

G-protein coupled receptors are ligand binding receptors that indirectly affect changes in the cell. The actual receptor is a single polypeptide that transverses the cell membrane seven times creating intracellular and extracellular loops. The extracellular loops create a ligand specific pocket which binds to neurotransmitters or hormones. The intracellular loops holds onto the G-protein.
G Protein-coupled Receptors01:15

G Protein-coupled Receptors

G Protein-Coupled Receptors or GPCRs are membrane-bound receptors that transiently associate with heterotrimeric G proteins and induce an appropriate response to sensory stimuli such as light, odors, hormones, cytokines, or neurotransmitters.
GPCRs are also called heptahelical, 7TM, or serpentine receptors, and consist of seven (H1-H7) transmembrane alpha-helices that span the bilayer to form a cylindrical core. The transmembrane helices are connected by three extracellular loops and three...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
G-Protein Gated Ion Channels01:21

G-Protein Gated Ion Channels

GPCRs are primarily responsible for our sense of smell, taste, and vision.  The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
GPCRs Regulate Adenylyl Cylase Activity01:09

GPCRs Regulate Adenylyl Cylase Activity

Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
IP3/DAG Signaling Pathway01:11

IP3/DAG Signaling Pathway

Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the  phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...