Orexin a phosphorylates the γ-Aminobutyric acid type A receptor β2 subunit on a serine residue and changes the surface expression of the receptor in SH-SY5Y cells exposed to propofol

Abstract

Propofol activates the γ-aminobutyric acid type A receptor (GABAAR) and causes a reversible neurite retraction, leaving a thin, thread-like structure behind; it also reverses the transport of vesicles in rat cortical neurons. The awakening peptide orexin A (OA) inhibits this retraction via phospholipase D (PLD) and protein kinase Ce{open} (PKCe{open}). The human SH-SY5Y cells express both GABAARs and orexin 1 and 2 receptors. These cells are used to examine the interaction between OA and the GABAAR. The effects of OA are studied with flow cytometry and immunoblotting. This study shows that OA stimulates phosphorylation on the serine residues of the GABAAR β2 subunit and that the phosphorylation is caused by the activation of PLD and PKCe{open}. OA administration followed by propofol reduces the cell surface expression of the GABAAR, whereas propofol stimulation before OA increases the surface expression. The GABAAR β2 subunit is important for receptor recirculation, and the effect of OA on propofol-stimulated cells may be due to a disturbed recirculation of the GABAAR.