Characterization of Structural Determinants of Type 1 Corticotropin Releasing Hormone (CRH) Receptor Signalling Properties

Mammalian adaptation to stressful stimuli requires activation of the type 1 corticotropin releasing hormone (CRH) receptor (CRH-R1), a 415 aminoacid protein that belongs to the large superfamily of 7 transmembrane domain receptors that relay signals across cells through activation of G-proteins. CRH-R1 expression and activity is regulated at the gene level by mRNA alternative splicing that results in a number of CRH-R1 variants. This process can generate putative CRH-R1 receptor variants with distinct structural and signaling properties; their study can provide important insights about the structural determinants of CRH-R1 functional characteristics. Using site-directed mutagenesis by overlap extension polymerase chain reaction (OE-PCR), we investigated the structure–function relationships of a CRH-R1 variant with an extended 1st intracellular loop (IC1) (CRH-R1β), a sequence modification that impairs signaling activity (such as cAMP production and MAPK activation). We identified a penta-aminoacid cassette within the 29-aminoacid insert of CRH-R1β rich in positive charged aminoacids (F¹⁷⁰ -R¹⁷⁴ ), as an important structural determinant for the impaired cAMP response.