Respective roles of calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMP) in cell surface expression of CRLR/RAMP heterodimeric receptors

J Biol Chem. 2002 Apr 26;277(17):14731-7. doi: 10.1074/jbc.M112084200. Epub 2002 Feb 19.

Abstract

Receptor activity modifying proteins RAMP1, RAMP2, and RAMP3 are responsible for defining affinity to ligands of the calcitonin receptor-like receptor (CRLR). It has also been proposed that receptor activity-modifying proteins (RAMP) are molecular chaperones required for CRLR transport to the cell surface. Here, we have studied the respective roles of CRLR and RAMP in transporting CRLR/RAMP heterodimers to the plasma membrane by using a highly specific binding assay that allows quantitative detection of cell surface-expressed CRLR or RAMP in the Xenopus oocytes expression system. We show that: (i) heterodimer assembly is not a prerequisite for efficient cell surface expression of CRLR, (ii) N-glycosylated RAMP2 and RAMP3 are expressed at the cell surface and their transport to the plasma membrane requires N-glycans, (iii) RAMP1 is not N-glycosylated and is transported to the plasma membrane only upon formation of heterodimers with CRLR, and (iv) introduction of N-glycosylation sites in the RAMP1 sequence (D58N/G60S, Y71N, and K103N/P105S) allows cell surface expression of these mutants at levels similar to that of wild-type RAMP1 co-expressed with CRLR. Our data argue against a chaperone function for RAMP and identify the role of N-glycosylation in targeting these molecules to the cell surface.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcitonin Receptor-Like Protein
  • Cell Membrane / metabolism
  • DNA, Complementary
  • Dimerization
  • Glycosylation
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins / genetics
  • Membrane Proteins / physiology*
  • Mice
  • Mutagenesis, Site-Directed
  • Receptor Activity-Modifying Protein 1
  • Receptor Activity-Modifying Protein 2
  • Receptor Activity-Modifying Protein 3
  • Receptor Activity-Modifying Proteins
  • Receptors, Calcitonin / physiology*
  • Xenopus

Substances

  • Calcitonin Receptor-Like Protein
  • Calcrl protein, mouse
  • DNA, Complementary
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Ramp1 protein, mouse
  • Ramp2 protein, mouse
  • Ramp3 protein, mouse
  • Receptor Activity-Modifying Protein 1
  • Receptor Activity-Modifying Protein 2
  • Receptor Activity-Modifying Protein 3
  • Receptor Activity-Modifying Proteins
  • Receptors, Calcitonin