Mapping the location of the growth hormone secretagogue receptor in the mouse brain using a novel fluorescent ligand

FRANCO BARRILE , NICOLÁS DE FRANCESCO, PAULA CORNEJO , MARIA JOSÉ TOLOSA , AGUSTINA CABRAL , GUADALUPE GARCÍA ROMERO, MIRTA REYNALDO , MARIO PERELLÓ

Congreso; XXXV Reunión Anual SAN2020; 2020

The growth hormone secretagogue receptor (GHSR) is a G-protein coupled receptorhighly expressed in the brain that modulates a variety of metabolic, endocrine, autonomicand behavioural functions. GHSR is activated by ghrelin and blocked by a liver-derivedhormone named Liver-expressed antimicrobial peptide 2 (LEAP2). Here, we developed anovel fluorescent GHSR ligand based on the N-terminal sequence of LEAP2, hereaftercalled FLEAP2, and assessed its capability to label GHSR in the mouse brain. We foundthat FLEAP2 impaired ghrelin-induced food intake in the same fashion that native LEAP2when administrated intracerebroventricularly (ICV) in mice. Furthermore, in mice ICVinjected with FLEAP2, we found that brain regions with the highest fluorescent signalwere the CA3 region of the hippocampus and the arcuate nucleus of the hypothalamus. Inorder to test the specificity of FLEAP2 towards GHSR labelling, we ICV injected micewith FLEAP2 after ICV pre-treatment with vehicle, native LEAP2 or ghrelin. We analysedthe level of fluorescent signal in the arcuate nucleus of these mice, as it is the brain regionwith highest GHSR expression, and mice pretreated with native LEAP2 or ghrelin hadlower fluorescent signal than vehicle pretreated mice. Thus, current data indicate thatFLEAP2 specifically binds to GHSR and is an appropriate tool to study LEAP2 binding andfunction in the mouse brain.