Tài liệu Báo cáo khoa học: Regulators of G-protein signalling are modulated by bacterial

Regulators of G-protein signalling are modulated by

bacterial lipopeptides and lipopolysaccharide

Sabine Riekenberg1

, Katja Farhat1

, Jennifer Debarry2

, Holger Heine2

, Gu¨ nther Jung3

, Karl-Heinz

Wiesmu¨ ller4 and Artur J. Ulmer1

1 Cellular Immunology, Department of Immunology and Cell Biology, Research Center Borstel, Germany

2 Innate Immunity, Department of Immunology and Cell Biology, Research Center Borstel, Germany

3 Institute of Organic Chemistry, University of Tuebingen, Germany

4 EMC microcollections GmbH, Tuebingen, Germany

The innate immune system is the first barrier against

pathogens and is initiated rapidly after recognition of

microbial products by receptors such as the Toll-like

receptors (TLR). TLR recognize a broad range of

ligands like lipopolysaccharides (LPS) and lipopeptides

(LP) representing pathogen-associated molecular

patterns [1,2]. TLR contain two major domains: the

extracellular ligand-binding domain, characterized by

leucine-rich repeats and the intracellular Toll ⁄IL-1

receptor domain (TIR domain) [3]. In mammals, 13

TLR homologues recognizing specific bacterial or viral

ligands have been identified [4]. Bacterial LP and LPS

are recognized by the membrane receptors TLR2 and

TLR4, respectively. Intracellular TLR3 is a receptor

for poly(I:C) [5], and CpG oligo-nucleotides are

ligands for the intracellular TLR9 [6,7]. TLR2 is

unique among all TLR, developing heteromers with

TLR1 and TLR6. In previous studies we investigated

the ligand specificity of different TLR2 dimers in

spleen cells from TLR2-, TLR6- and TLR1-deficient

mice [8,9]. LP have strong TLR2-dependency but differ

in their requirement for TLR6 and TLR1, according

Keywords

gene expression; lipopeptides;

macrophages; regulator of G-protein

signalling; Toll-like receptors

Correspondence

A. J. Ulmer, Cellular Immunology and Cell

Biology, Research Center Borstel, Parkallee

22, 23845 Borstel, Germany

Fax: +49 4537 188435

Tel: +49 4537 188448

E-mail: [email protected]

(Received 26 August 2008, revised 12

November 2008, accepted 20 November

2008)

doi:10.1111/j.1742-4658.2008.06813.x

Regulators of G-protein signalling accelerate the GTPase activity of Ga

subunits, driving G proteins in their inactive GDP-bound form. This

property defines them as GTPase activating proteins. Here the effect of

different Toll-like receptor agonists on RGS1 and RGS2 expression in

murine bone marrow-derived macrophages and J774 cells was analysed.

After stimulation with TLR2 ⁄ 1 or TLR2 ⁄ 6 lipopeptide ligands and the

TLR4 ⁄MD2 ligand lipopolysaccharide, microarray analyses show only

modulation of RGS1 and RGS2 among all the regulators of G-protein sig￾nalling tested. Real-time PCR confirmed modulation of RGS1 and RGS2.

In contrast to RGS2, which was always downregulated, RGS1 mRNA was

upregulated during the first 30 min after stimulation, followed by downre￾gulation. Similar results were also found in the murine macrophage cell line

J774. The ligand for intracellular TLR9 modulates RGS1 and RGS2 in a

similar manner. However, the TLR3 ligand poly(I:C) permanently upregu￾lates RGS1 and RGS2 expression indicating a different modulation by the

MyD88- and TRIF-signalling pathway. This was confirmed using

MyD88) ⁄ ) and TRIF) ⁄ ) bone marrow-derived macrophages. Modulation

of RGS1 and RGS2 by Toll-like receptor ligands plays an important role

during inflammatory and immunological reactions after bacterial and viral

infection.

Abbreviations

BMDM, bone marrow-derived macrophages; FSL-1, fibroblast-stimulating lipopeptide-1; GAP, GTPase activating protein; GPCR, G-protein

coupled receptor; LP, lipopeptide; LPS, lipopolysaccharide; RGS, regulator of G-protein signalling; TLR, Toll-like receptor.

FEBS Journal 276 (2009) 649–659 ª 2008 Research Center Borstel. Journal compilation ª 2008 FEBS 649