γ-Amino Butyric Acid Type B Receptors Stimulate Neutrophil Chemotaxis during Ischemia-Reperfusion

Abstract

Serine/threonine kinase Akt, or protein kinase B, has been shown to regulate a number of neutrophil functions. We sought to identify Akt binding proteins in neutrophils to provide further insights into understanding the mechanism by which Akt regulates various neutrophil functions. Proteomic and immunoprecipitation studies identified γ-amino butyric acid (GABA) type B receptor 2 (GABABR2) as an Akt binding protein in human neutrophils. Neutrophil lysates subjected to Akt immunoprecipitation followed by immunoblotting with anti-GABABR2 demonstrated Akt association with the intact GABABR. Similar results were obtained when reciprocal immunoprecipitations were performed with anti-GABABR2 Ab. Additionally, GABABR2 and Akt colocalization was demonstrated by confocal microscopy. A GABABR agonist, baclofen, activated Akt and stimulated neutrophil-directed migration in a PI3K-dependent manner, whereas CGP52432, a GABABR antagonist blocked such effects. Baclofen, stimulated neutrophil chemotaxis and tubulin reorganization in a PI3K-dependent manner. Additionally, a GABABR agonist failed to stimulate neutrophil superoxide burst. We are unaware of the association of GABABR with Akt in any cell type. The present study shows for the first time that a brain-specific receptor, GABABR2 is present in human neutrophils and that it is functionally associated with Akt. Intraventricular baclofen pretreatment in rats subjected to a stroke model showed increased migration of neutrophils to the ischemic lesion. Thus, the GABABR is functionally expressed in neutrophils, and acts as a chemoattractant receptor via an Akt-dependent pathway. The GABABR potentially plays a significant role in the inflammatory response and neutrophil-dependent ischemia-reperfusion injury such as stroke.

Immunological GABAergic interactions and therapeutic applications in autoimmune diseases

“…As noted above, the GABAergic responses of human DCs are similar to those of mice [31]. Neutrophils express GABA A R and GABA B R receptors, and it appears that type B receptors can stimulate neutrophilic chemotaxis [33].…”

The Neurotransmitter GABA Is a Potent Inhibitor of the Stromal Cell-Derived Factor-1αInduced Migration of Adult CD133+Hematopoietic Stem and Progenitor Cells

“…Two recent studies suggest a role for GABA in inflammatory conditions. GABA Breceptor expression was detected on neutrophil granulocytes and acts as a chemoattractant receptor via an Aktdependent pathway (28). An increased migration of neutrophil granulocytes to the ischemic lesion was observed after intraventricular baclofen pretreatment in rats subjected to a stroke model.…”

Effects of genetic and environmental factors and gene-environment interaction on expression variations of genes related to stroke in rat brain

“…The GABA-B receptors potentially play an important role in the inflammatory response and neutrophil-dependent ischemia-reperfusion injury such as stroke [59]. Another example is that the TrkB receptor, a high-affinity receptor of two neurotrophins (brain-derived neurotrophic factor and neurotrophin 4/5), is important for neuronal growth and differentiation and regulation of synaptic transmission and for prevention from neuronal damage after ischemia [60,61]. In our microarray data genes for the full-length (FL) and the truncated TrKB showed differential expressions between SHRSR and SHRSP even though their differential expression direction is just opposite (supplemental Table 1).…”