Conditional Mutagenesis of G-Protein Coupled Receptors and G-Proteins

Abstract

The G-protein-coupled receptor signaling system, consisting of a huge variety of receptors as well as of many G-proteins and effectors, operates in every cell and is involved in many physiological and pathological processes. The versatility of this system and the involvement of specific components makes G-protein-coupled receptors and their signaling pathways ideal targets for pharmacological interventions. Classical mouse knockout models have often provided important preliminary insights into the biological roles of individual receptors and signaling pathways and they are routinely used in the process of target validation. The recent development of efficient conditional mutagenesis techniques now allows a much more detailed analysis of G-protein-mediated signaling transduction processes. This review summarizes some of the areas in which progress has recently been made by applying conditional mutagenesis of genes coding for G-proteins and G-protein-coupled receptors.

Heterotrimeric G proteins, focal adhesion kinase, and endothelial barrier function

“…Several studies have used pertussis toxin (Ptx) to assess the impact of Gi proteins in regulating endothelial barrier function, but these results have not been conclusive because Ptx prevents GDP release from the Gαi subunit, as well as alters Gβγ function (Smrcka, 2008). Global and endothelial specific deletion of Gα13 in mice resulted in embryonic lethality (Offermanns, 2007), hampering the analysis of its role in regulating endothelial barrier function. Recently, Offermanns’ group generated mice in which Gαq/Gα11- and Gα12/Gα13-mediated signaling pathways can be conditionally deleted in endothelial cells by inducing Tie2-Cre recombinase activity (Korhonen et al, 2009).…”

“…Heterotrimeric G proteins consisting of Gα and Gβγ subunits regulate a variety of endothelial functions including migration, proliferation, differentiation, survival, and tissue-fluid homeostasis (Hamm, 1998; Wieland and Mittmann, 2003; Shajahan et al, 2004; Andreeva et al, 2005; Andreeva et al, 2006; Offermanns, 2007; Knezevic et al, 2009; Liu et al, 2009). These proteins act as an intracellular partner downstream of seven-transmembrane domain G protein coupled receptors (GPCRs), the largest family of membrane proteins within the human genome, to transmit diverse signals from extracellular GPCR ligands (Gilman, 1987; Hamm, 1998; Offermanns, 2007).…”

“…These proteins act as an intracellular partner downstream of seven-transmembrane domain G protein coupled receptors (GPCRs), the largest family of membrane proteins within the human genome, to transmit diverse signals from extracellular GPCR ligands (Gilman, 1987; Hamm, 1998; Offermanns, 2007). Thus far 16 genes encode for 23 known Gα proteins which are divided into four major classes based on sequence homology: Gα (s/olf), Gα (i1/i2/i3/o/ t-rod/ t-cone/gust/z), Gα (q/11/14/16), and Gα (12/13) (Simon et al, 1991).…”

Deciphering the specific role of Gαi/o isoforms: functional selective oxytocin ligands and somatostatin SST5 receptor mutants

“…Gene ablation in mice is a powerful approach to identify functions of proteins and it has been extensively applied to all G αi/o isoforms with quite unexpected results [7]. G αi1 -and G αi3 -deficient mice are viable and fertile, whereas the inactivation of the G αi2 leads to increased peri-and post-natal mortality.…”