PT  - JOURNAL ARTICLE
AU  - Madhara Udawela
AU  - George Christopoulos
AU  - Maria Morfis
AU  - Arthur Christopoulos
AU  - Siying Ye
AU  - Nanda Tilakaratne
AU  - Patrick M. Sexton
TI  - A Critical Role for the Short Intracellular C Terminus in Receptor Activity-Modifying Protein Function
AID  - 10.1124/mol.106.024257
DP  - 2006 Nov 01
TA  - Molecular Pharmacology
PG  - 1750--1760
VI  - 70
IP  - 5
4099  - http://molpharm.aspetjournals.org/content/70/5/1750.short
4100  - http://molpharm.aspetjournals.org/content/70/5/1750.full
SO  - Mol Pharmacol2006 Nov 01; 70
AB  - Receptor activity-modifying proteins (RAMPs) interact with and modify the behavior of the calcitonin receptor (CTR) and calcitonin receptor-like receptor (CLR). We have examined the contribution of the short intracellular C terminus, using constructs that delete the last eight amino acids of each RAMP. C-Terminal deletion of individual RAMPs had little effect on the signaling profile induced when complexed with CLR in COS-7 or human embryonic kidney (HEK)293 cells. Likewise, confocal microscopy revealed each of the mutant RAMPs translocated hemagglutinin-tagged CLR to the cell surface. In contrast, a pronounced effect of RAMP C-terminal truncation was seen for RAMP/CTRa complexes, studied in COS-7 cells, with significant attenuation of amylin receptor phenotype induction that was stronger for RAMP1 and -2 than RAMP3. The loss of amylin binding upon C-terminal deletion could be partially recovered with overexpression of Gαs, suggesting an impact of the RAMP C terminus on coupling of G proteins to the receptor complex. In HEK293 cells the c-Myc-RAMP1 C-terminal deletion mutant showed high receptor-independent cell surface expression; however, this construct showed low cell surface expression when expressed alone in COS-7 cells, indicating interaction of RAMPs with other cellular components via the C terminus. This mutant also had reduced cell surface expression when coexpressed with CTR. Thus, this study reveals important functionality of the RAMP C-terminal domain and identifies key differences in the role of the RAMP C terminus for CTR versus CLR-based receptors. The American Society for Pharmacology and Experimental Therapeutics