Glycogen Synthase Kinase-3 modulates α-adrenergic receptor action and regulation.

The possibility that glycogen synthase kinase 3 (GSK3) could modulate α-adrenergic receptor (α-AR) function and regulation was tested employing LNCaP and HEK293 cells transfected to express the enhanced green fluorescent protein-tagged human α-AR. Receptor phosphorylation and internalization, intracellular free calcium, α-AR-GSK3 colocalization, and coimmunoprecipitation were studied. The effects of the pharmacological GSK3 inhibitor, SB-216763, and the coexpression of a dominant-negative mutant of this kinase, as well as the signaling, desensitization, and internalization of receptors with S229, S258, S352, and S381 substitutions for alanine or aspartate, were also determined.

Sites phosphorylated in human α-adrenoceptors in response to noradrenaline and phorbol myristate acetate.

Phosphorylation of the human α-adrenergic receptor (fused with the green fluorescent protein) was studied employing the inducible Flp-ln HEK293 T-Rex system for expression. Serine/alanine substitutions were performed in five sites corresponding to those previously identified as phosphorylation targets in the hamster ortholog. Desensitization was decreased in these mutants but receptor phosphorylation was still clearly detected.

The role of β-arrestins in G protein-coupled receptor heterologous desensitization: A brief story.

G protein-coupled receptors (GPCRs) are transmembrane proteins that have an important impact in a myriad of cellular functions. Posttranslational modifications on GPCRs are a key processes that allow these proteins to recruit other intracellular molecules. Among these modifications, phosphorylation is the most important way of desensitization of these receptors.

Distinct phosphorylation sites/clusters in the carboxyl terminus regulate α-adrenergic receptor subcellular localization and signaling.

The human α-adrenergic receptor is a seven transmembrane-domain protein that mediates many of the physiological actions of adrenaline and noradrenaline and participates in the development of hypertension and benign prostatic hyperplasia. We recently reported that different phosphorylation patterns control α-adrenergic receptor desensitization. However, to our knowledge, there is no data regarding the role(s) of this receptor's specific phosphorylation residues in its subcellular localization and signaling.

Dissecting the signaling features of the multi-protein complex GPCR/β-arrestin/ERK1/2.

G protein-coupled receptors (GPCRs) have emerged as key biological entities that regulate a plethora of physiological processes and participate in the onset and development of many diseases. Moreover, these receptors are important targets of almost 25% of the current therapeutic drugs in the market. Upon agonist binding, GPCRs activate a great number of signaling pathways, resulting in important cellular events like gene transcription, survival, proliferation and differentiation.

Different phosphorylation patterns regulate α-adrenoceptor signaling and desensitization.

Human α-adrenoceptors (α-ARs) are a group of the seven transmembrane-spanning proteins that mediate many of the physiological and pathophysiological actions of adrenaline and noradrenaline. Although it is known that α-ARs are phosphoproteins, their specific phosphorylation sites and the kinases involved in their phosphorylation remain largely unknown. Using a combination of in silico analysis, mass spectrometry and site directed mutagenesis, we identified distinct α-AR phosphorylation patterns during noradrenaline- or phorbol ester-mediated desensitizations.

Protein Kinase C Activation Promotes α-Adrenoceptor Internalization and Late Endosome Trafficking through Rab9 Interaction. Role in Heterologous Desensitization.

Upon agonist stimulation, -adrenergic receptors couple to G proteins, calcium signaling and protein kinase C activation; subsequently, the receptors are phosphorylated, desensitized, and internalized. Internalization seems to involve scaffolding proteins, such as -arrestin and clathrin. However, the fine mechanisms that participate remain unsolved.