The Pseudo signal peptide of the corticotropin-releasing factor receptor type 2A prevents receptor oligomerization.
N-terminal signal peptides mediate the interaction of native proteins with the translocon complex of the endoplasmic reticulum membrane and are cleaved off during early protein biogenesis. The corticotropin-releasing factor receptor type 2a (CRF(2(a))R) possesses an N-terminal pseudo signal peptide, which represents a so far unique domain within the large protein family of G protein-coupled receptors (GPCRs). In contrast to a conventional signal peptide, the pseudo signal peptide remains uncleaved and consequently forms a hydrophobic extension at the N terminus of the receptor. The functional consequence of the presence of the pseudo signal peptide is not understood. Here, we have analyzed the significance of this domain for receptor dimerization/oligomerization in detail. To this end, we took the CRF(2(a))R and the homologous corticotropin-releasing factor receptor type 1 (CRF(1)R) possessing a conventional cleaved signal peptide and conducted signal peptide exchange experiments. Using single cell and single molecule imaging methods (fluorescence resonance energy transfer and fluorescence cross-correlation spectroscopy, respectively) as well as biochemical experiments, we obtained two novel findings; we could show that (i) the CRF(2(a))R is expressed exclusively as a monomer, and (ii) the presence of the pseudo signal peptide prevents its oligomerization. Thus, we have identified a novel functional domain within the GPCR protein family, which plays a role in receptor oligomerization and which may be useful to study the functional significance of this process in general.
Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
Anke
A
Teichmann
Claudia
C
Rutz
Annika
A
Kreuchwig
Gerd
G
Krause
Burkhard
B
Wiesner
Ralf
R
Schülein
D001704:Biopolymers; D002460:Cell Line; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D021382:Protein Sorting Signals; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism*; D000099052:CRF Receptor, Type 1
D001704:Biopolymers; D021382:Protein Sorting Signals; D018019:Receptors, Corticotropin-Releasing Hormone; D000099052:CRF Receptor, Type 1; D003346:Corticotropin-Releasing Hormone