title: The corticotropin-releasing factor receptor type 2a contains an N-terminal pseudo signal peptide.
abstract: The corticotropin-releasing factor receptor type 2a (CRF(2(a)) receptor) belongs to the family of G protein-coupled receptors. The receptor possesses a putative N-terminal signal peptide that is believed to be cleaved-off after mediating the endoplasmic reticulum targeting/insertion process, like the corresponding sequence of the homologous CRF(1) receptor. Here, we have assessed the functional significance of the putative signal peptide of the CRF(2(a)) receptor and show that it is surprisingly completely incapable of mediating endoplasmic reticulum targeting, despite meeting all sequence criteria for a functional signal by prediction algorithms. Moreover, it is uncleaved and forms part of the mature receptor protein. Replacement of residue Asn(13) by hydrophobic or positively charged residues converts the sequence into a fully functional and cleaved signal peptide demonstrating that conventional signal peptide functions are inhibited by a single amino acid residue. Deletion of the domain leads to an increase in the amount of immature, intracellularly retained receptors demonstrating that the sequence has adopted a new function in receptor trafficking through the early secretory pathway. Taken together, our results identify a novel hydrophobic receptor domain in the family of the heptahelical G protein-coupled receptors and the first pseudo signal peptide of a eukaryotic membrane protein. Our data also show that the extreme N termini of the individual CRF receptor subtypes differ substantially.
authors.affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rutz
authors.forename: Armin
authors.initials: A
authors.lastname: Renner
authors.forename: Martina
authors.initials: M
authors.lastname: Alken
authors.forename: Katharina
authors.initials: K
authors.lastname: Schulz
authors.forename: Michael
authors.initials: M
authors.lastname: Beyermann
authors.forename: Burkhard
authors.initials: B
authors.lastname: Wiesner
authors.forename: Walter
authors.initials: W
authors.lastname: Rosenthal
authors.forename: Ralf
authors.initials: R
authors.lastname: Schülein
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D051381:Rats; D018019:Receptors, Corticotropin-Releasing Hormone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D021382:Protein Sorting Signals; D018019:Receptors, Corticotropin-Releasing Hormone; C499434:corticotropin-releasing factor receptor type 2a, rat