Hemopressin is an inverse agonist of CB ₁ cannabinoid receptors

Abstract

To date, the endogenous ligands described for cannabinoid receptors have been derived from membrane lipids. To identify a peptide ligand for CB 1 cannabinoid receptors, we used the recently described conformation-state sensitive antibodies and screened a panel of endogenous peptides from rodent brain or adipose tissue. This led to the identification of hemopressin (PVNFKFLSH) as a peptide ligand that selectively binds CB 1 cannabinoid receptors. We find that hemopressin is a CB 1 receptor-selective antagonist, because it is able to efficiently block signaling by CB 1 receptors but not by other members of family A G protein-coupled receptors (including the closely related CB2 receptors). Hemopressin also behaves as an inverse agonist of CB 1 receptors, because it is able to block the constitutive activity of these receptors to the same extent as its well characterized antagonist, rimonabant. Finally, we examine the activity of hemopressin in vivo using different models of pain and find that it exhibits antinociceptive effects when administered by either intrathecal, intraplantar, or oral routes, underscoring hemopressin's therapeutic potential. These results represent a demonstration of a peptide ligand for CB 1 cannabinoid receptors that also exhibits analgesic properties. These findings are likely to have a profound impact on the development of novel therapeutics targeting CB 1 receptors.

Post-activation-mediated Changes in Opioid Receptors Detected by N-terminal Antibodies

“…We recently used antibodies to the N terminus of CB 1 cannabinoid receptors (that exhibit increased recognition of agonist-treated receptors) to screen for peptidic ligands to this receptor. This led to the identification of hemopressin as a selective peptidic inverse agonist of CB 1 receptors (32). Using this peptide antagonist we have been able to demonstrate the activity of endogenous CB 1 receptors in an intracellular compartment (33).…”

Intracellular Peptides as Natural Regulators of Cell Signaling

“…We have previously shown that catalytically inactive oligopeptidase EP24.15 is suitable for the isolation of novel bioactive peptides (22,47). Most of these peptides have 5-16 amino acid residues, are fragments of intracellular proteins, and contain a putative protein kinase post-translational modification site (22,23,31).…”

Endogenous Peptide Discovery of the Rat Circadian Clock

“…Although peptides that are protein fragments could result from post-mortem degradation during sample preparation, they may be the products of prohormone processing that are physiologically relevant. For example, small peptides formed from hemoglobin, the hemopressins, have known bioactivity and are likely enzymatically produced and are not formed during post-mortem degradation (57)(58)(59). Fig.…”