Biomimetric screening of CRH receptor ligands

The 41-amino acid peptide Corticotropin-Releasing Hormone (CRH) is a major regulator of the body’s response to stress. Identified originally as the neuroendocrine factor initiating the hypothalamus-pituitary-adrenal axis (HPA), CRH-containing neurons have subsequently been shown to project to various regions in the central nervous system that are involved in mood and stress-related behavior. Injection of CRH into selected brain areas in mice leads to a state of enhanced anxiety, whereas the response to stressful stimuli can be reduced by administering CRHR1 antagonists. The functional role of CRH in stress-coping behavior is further supported by transgenic animals lacking the CRH1 receptor or over-expressing CRH. The observations of HPA axis hyperreactivity and enhanced CRH levels in the cerebrospinal fluid of depressed patients further suggest a dysfunction of the CRH system in affective disorders.

The CRH receptors are G-Protein Coupled Receptors (GPCRs) of the secretin family (class B1). Members of this subfamily are characterized by a conserved extracellular domain, large peptide hormone ligands (27-84aa) and their involvement in endocrinological functions. Most class B-GPCRs work by a common mechanism termed the ‘two-domain’ model. With their extracellular domain they tightly bind to carboxyl-terminal regions of their peptide ligands. This induces a second, low-affinity interaction between the N-terminus of the peptide with the transmembrane helices of the receptor (juxtamembrane domain) that induces a structural rearrangement leading to intracellular signal transduction.

Fig. 1: Two-Domain Mechanism of CRH Receptor Binding and Activation: The extracellular domain of the CRH receptor (dark blue) binds with high affinity to the C-terminal part of the peptide ligand (dark green). This recruits the low-affinity, N-terminal effector part of the peptide ligand (light green) to the transmembrane helices (light blue) and induces their structural rearrangement leading to intracellular signalling (e.g., G-protein activation).

We plan to use the two-domain model of CRH receptor activation for a biomimetic screening system. The C-terminal part of the endogenous hormone ligand is attached to a library of peptides, peptidomimetics or small molecule fragments. The resulting conjugates are tested for activation of the receptor. In this setup, the C-terminal part of the endogenous hormone ligand serves as a high affinity carrier that positions the tethered probe molecules in the vicinity of the transmembrane helices. This allows even very weak interactions with the juxtamembrane domain to be measured.

Research groups involved:

RG Felix Hausch: Bastiaan Hoogeland, Christian Devigny, Stephanie Robu

AG Jan Deussing

Publikations:

Devigny C, Perez-Balderas F, Hoogeland B, Cuboni S, Wachtel R, Mauch CP, Webb KJ, Deussing JM, Hausch F (2011) Biomimetic screening of class-B g protein-coupled receptors, JACS, 133/23, 8927-33.

Paez-Pereda M, Hausch F, Holsboer F (2011) Corticotropin releasing factor receptor antagonists for major depressive disorder, Expert Opin Investig Drugs, 20/4, 519-35F.

Hausch (2008) Betablockers at Work: the Crystal Structure of the 2-Adrenergic Receptor. Angewandte Chemie International Edition, 47:2-5.