Die Funktionelle Rolle der Palmitilierung des 5-HT 1A Rezeptor
The Functional Role of Palmitoylation of the 5-HT 1A receptor
by Ekaterina Papoucheva
Date of Examination:2004-11-03
Date of issue:2005-04-08
Advisor:Prof. Dr. Evgeni Ponimaskin
Referee:Prof. Dr. Diethelm Richter
Referee:Prof. Dr. Reinhard Jahn
Referee:Prof. Dr. Friedrich-Wilhelm Schürmann
Persistent Address:
http://dx.doi.org/10.53846/goediss-64
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Abstract
English
In the present study, we verified that the mouse 5-hydroxytryptamine(1A) (5-HT(1A)) receptor is modified by palmitic acid, which is covalently attached to the protein through a thioester-type bond. Palmitoylation efficiency was not modulated by receptor stimulation with agonists. Block of protein synthesis by cycloheximide resulted in a significant reduction of receptor acylation, suggesting that palmitoylation occurs early after synthesis of the 5-HT(1A) receptor. Furthermore, pulse-chase experiments demonstrated that fatty acids are stably attached to the receptor. Two conserved cysteine residues 417 and 420 located in the proximal C-terminal domain were identified as acylation sites by site-directed mutagenesis. To address the functional role of 5-HT(1A) receptor acylation, we have analyzed the ability of acylation-deficient mutants to interact with heterotrimeric G(i) protein and to modulate downstream effectors. Replacement of individual cysteine residues (417 or 420) resulted in a significantly reduced coupling of receptor with G(i) protein and impaired inhibition of adenylyl cyclase activity. When both palmitoylated cysteines were replaced, the communication of receptors with G alpha(i) subunits was completely abolished. Moreover, non-palmitoylated mutants were no longer able to inhibit forskolin-stimulated cAMP formation, indicating that palmitoylation of the 5-HT(1A) receptor is critical for the enabling of G(i) protein coupling/effector signaling. The receptor-dependent activation of extracellular signal-regulated kinase was also affected by acylation-deficient mutants, suggesting the importance of receptor palmitoylation for the signaling through the G beta gamma-mediated pathway, in addition to the G alpha(i)-mediated signaling.
Keywords: G-protein-coupled receptor; palmitoylation; serotonin
Other Languages
In dieser Studie wurde demonstriert, dass der 5-HT (1A) Rezeptor durch tioester-type Bindung palmitoyliert ist. Die Palmitoylierung wird nicht durch die Stimulation mit den Agonisten moduliert. Durch die Proteinsynthese Blockierung wurde gezeigt dass die Palmitilierung abhängig von der Proteinsynthese ist . Die pulse-chase Experimente demonstrieren dass die Rezeptormodifikation Stabil ist. Die zwei konservierten Cysteine 417 und 420 im C-terminal des Rezeptor wurden als potentiale Palmitoylierungsstellen identifiziert. Dies wurde durch die ortspezifische Mutagenese nachgewiesen. Die Funktionale Analyse von acylierungsdeffizienten Mutanten hat eine kritische Rolle der C-terminal Palmitoylierung für die Rezeptor- G-protein-kopplung und die Receptor-spezifischen Signale wie cAMP Synthese Inhibierung und die Erk1/2 Stimulation gezeigt.
Schlagwörter: G-proteine-gekoppelte Rezeptor; Palmitoylierung; Serotonin
