The GABA _B receptor interacts directly with the related transcription factors CREB2 and ATFx

Abstract

␥-Aminobutyric acid type B (GABAB) receptors mediate the metabotropic actions of the inhibitory neurotransmitter GABA. These seven-transmembrane receptors are known to signal primarily through activation of G proteins to modulate the action of ion channels or second messengers. The functional GABAB receptor is made up of a heterodimer consisting of two subunits, GABAB-R1 and GABA B-R2, which interact via coiled-coil domains in their C-terminal tails. By using a yeast two-hybrid approach, we have identified direct interactions between the C-terminal tails of GABAB-R1 and GABAB-R2 with two related transcription factors, CREB2 (ATF4) and ATFx. In primary neuronal cultures as well in recombinant Chinese hamster ovary cells expressing GABAB receptors, CREB2 is localized within the cytoplasm as well as the nucleus. Activation of the GABAB receptor by the specific agonist baclofen leads to a marked translocation and accumulation of CREB2 from the cytoplasm into the nucleus. We demonstrate that receptor stimulation results in activation of transcription from a CREB2 responsive reporter gene. Such a signaling mechanism is unique among Family C G protein-coupled receptors and, in the case of the GABAB receptor and CREB2, may play a role in long-term changes in the nervous system. G ABA (␥-aminobutyric acid) is the major inhibitory neurotransmitter activating both ionotrophic GABA A and GABA C receptors as well as metabotropic GABA B receptors (1). GABA B receptors were originally identified pharmacologically (2) and couple through G proteins to Ca 2ϩ or K ϩ channels. Despite being recognized many years ago, the molecular nature of the GABA B receptor has been elucidated only recently (3-8). The initial GABA B ''receptor,'' GABA B -R1, was expression cloned by using a high-affinity antagonist and showed homology to Family C G protein-coupled receptors (GPCRs), such as metabotropic glutamate receptors, with a characteristically large extracellular N-terminal domain as well as a seven-transmembrane topology (3). However, when expressed recombinantly, GABA B -R1 failed to reproduce the expected agonist affinities (3, 5) and was not expressed at the cell surface (5, 9), suggesting that a component was lacking from GABA B -R1 for reconstitution of the functional receptor. Subsequent studies confirmed that a second distinct but related GPCR, GABA B -R2, heterodimerizes with GABA B -R1 to create the GABA B -receptor (4-8). Yeast two-hybrid (YTH) studies showed that the two receptors interact through a coiled-coil domain within their respective C-terminal tails (5, 7, 10), and in situ hybridization analysis showed colocalization of the two receptors (4, 5, 7, 10). The expressed heterodimer reproduced expected agonist pharmacology, and in the presence of GABA B -R2, GABA B -R1 was trafficked to the cell surface. Moreover, effector couplings to K ϩ and Ca 2ϩ channels have now been demonstrated by using the heterodimeric receptor (4,6,11,12).We previously used a YTH screen to identify GABA B -R2 as an interacting protein partner to G...

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

“…Additionally, confocal staining identified GABA B R2 in the cytosol, plasma membrane, epicenter of the cell, and in the nucleus of neutrophils. Detection of GABA B R2 in the nucleus was surprising; however, GABA B R2 has been shown previously to interact with nuclear proteins such as transcription factors CREB2 and activating transcription factor x and factor 4 (33,34).…”

The DISC locus in psychiatric illness

“…ATF4 has many other diverse cellular roles including regulation of presenilin 1 expression, developmentally regulated metabotropic GABA(B) receptor binding 212 in mouse brain and cultured neurons, [213][214][215] and regulation of GABA(B) promoter activity. 216 DISC1 may therefore influence neuronal signalling via its interaction with ATF4.…”

Expression profiling in monozygotic twins discordant for bipolar disorder reveals dysregulation of the WNT signalling pathway

“…At best, when considering a fold-change minimum of X1.3 in our data, there were two genes (C6ORF32, ATF5) that showed the same direction of gene expression difference in two out of three of our twin pairs, with the direction of change in the two twin pairs from the work of Kakiuchi et al 1 Of potential interest here is ATF5, a related family member to ATF6 which is involved in the transcriptional regulation of ER response genes, such as XBP1 and HSPA5. 1 Although there is no direct evidence to indicate a role for ATF5 in regulating the ER stress response, this transcription factor is known to directly interact with the g-aminobutyric acid B receptor 1 42 and the product of the putative schizophrenia susceptibility locus disrupted-in-schizophrenia (DISC1). 43 Although highly speculative, either of these molecular interactions could conceivably contribute to the development of BD1 through altered neuronal signalling.…”