Internalization and trafficking of the human and rat growth hormone-releasing hormone receptor
Article first published online: 21 OCT 2004
Copyright © 2004 Wiley-Liss, Inc.
Journal of Cellular Physiology
Volume 203, Issue 2, pages 335–344, May 2005
How to Cite
Veyrat-Durebex, C., Pomerleau, L., Langlois, D. and Gaudreau, P. (2005), Internalization and trafficking of the human and rat growth hormone-releasing hormone receptor. J. Cell. Physiol., 203: 335–344. doi: 10.1002/jcp.20233
- Issue published online: 23 FEB 2005
- Article first published online: 21 OCT 2004
- Manuscript Accepted: 19 AUG 2004
- Manuscript Received: 7 MAY 2004
- Canadian Institutes of Health Research
Internalization and intracellular trafficking of the growth hormone-releasing hormone receptor (GHRH-R) were studied in rat anterior pituitary and human (h) and rat (r) GHRH-R-transfected BHK cells, with the GHRH agonist, [Nα-5-carboxyfluoresceinyl-D-Ala2, Ala8, Ala15, Lys22]hGHRH(1-29)NH2 (Fluo-GHRH). Time- and temperature-dependent internalization of stimulated GHRH-R was blocked by phenyl arsine oxide (PAO) in both cell types. In anterior pituitary and rGHRH-R-transfected BHK cells, only filipin III and cerulenin blocked receptor-mediated internalization of Fluo-GHRH while in hGHRH-R-transfected BHK cells, only hyperosmolar sucrose inhibited this process. These results suggest that hGHRH-R internalization is clathrin-dependent, while fatty acid acylation of rGHRH-R appears to be a prerequisite to caveolin-dependent internalization. Experiments in anterior pituitary using Bodipy-FL-C5 ganglioside GM1, a specific marker of lipid rafts such as caveolae, confirmed this latter pathway. Co-localization of Fluo-GHRH with LysoTracker indicated that Fluo-GHRH was directed to acidic organelles in both cell types. Finally, studies using cycloheximide and monensin showed that upon stimulation with GHRH, an optimal concentration of functional GHRH-R was maintained at the plasma membrane due to de novo synthesis and recycling in pituitary cells and to de novo synthesis solely in hGHRH-R-transfected BHK cells. This first study on the dynamics of the GHRH/GHRH-R complexes using fluorescence imaging in a native environment compared to cell system models, revealed that both receptor primary structure and concentration at the plasma membrane play important roles in internalization and trafficking of specific G-protein-coupled receptors (GPCR). © 2004 Wiley-Liss, Inc.