tailieunhanh - Báo cáo khoa học: Human d opioid receptor biogenesis is regulated via interactions with SERCA2b and calnexin

arco(endo)plasmic reticulum calcium ATPase (SERCA)2b maintains the cellular Ca 2+ homeostasis by transferring Ca 2+ from the cytosol to the lumen of the endoplasmic reticulum (ER). Recently, SERCA2b has also been shown to be involved in the biosynthesis of secreted and membrane proteins via direct protein–protein interactions, involving components of the ER folding and quality-control machinery, as well as newly synthesized G protein-coupled receptors. | ỊFEBS Journal Human Ô opioid receptor biogenesis is regulated via interactions with SERCA2b and calnexin Jussi T. Tuusa Tarja T. Leskela and Ulla E. Petaja-Repo Department of Anatomy and CellBiology Institute of Biomedicine University of Oulu Finland Keywords calnexin endoplasmic reticulum G protein-coupled receptor GPCR opioid receptor sarco endo plasmic reticulum calcium ATPase SERCA Correspondence Ulla Petaja-Repo Department of Anatomy and CellBiology Institute of Biomedicine University of Oulu PO Box 5000 FI-90014 Oulu Finland Fax 358 8 537 5172 Tel 358 8 537 5193 E-mail Received 22 February 2010 revised 22 April 2010 accepted 27 April 2010 doi Sarco endo plasmic reticulum calcium ATPase SERCA 2b maintains the cellular Ca2 homeostasis by transferring Ca2 from the cytosol to the lumen of the endoplasmic reticulum ER . Recently SERCA2b has also been shown to be involved in the biosynthesis of secreted and membrane proteins via direct protein-protein interactions involving components of the ER folding and quality-control machinery as well as newly synthesized G protein-coupled receptors. Here we demonstrate that the human delta opioid receptor hỗOR exists in a ternary complex with SERCA2b and the ER molecular chaperone calnexin. The interaction between SERCA2b and hỗOR in vivo did not require calnexin as it was independent of the C-termi-nal calnexin-interacting domain of SERCA2b. However the receptor was able to mediate co-immunoprecipitation of calnexin with the C-terminally truncated SERCA2b. The association of SERCA2b with hỗOR was regulated in vitro by Ca2 and ATP in a manner that was opposite to the caln-exin-hỗOR interaction. Importantly co-expression of the catalytically inactive SERCA2b D351A or calnexin binding-compromised SER-CA2bAC mutants with the receptor decreased the expression of mature receptors in a manner that did not directly relate to changes in the ER Ca2 concentration. We conclude .