Ghrelin receptor (GHSR1a) constitutive and ghrelin-evoked activities inhibit calcium channels through different signalling pathways.

MARTÍNEZ DAMONTE V; LOPEZ SOTO JE; AGOSTI F; MUSTAFÁ ER; RODRÍGUEZ SS; RAINGO J

Huerta Grande

Congreso; XXVIII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2013

Sociedad Argentina de Neurociencia

GHSR1a is a G-protein coupled receptor (GPCR) highly expressed at the hypothalamus and by contrast to the most GPCRs, it exerts a high constitutive activity. GHSR1a activity enhances neuronal excitability by acting on several postsynaptic structures. This receptor is also present at axonal terminals, but its physiological impact and the molecular mechanisms involved in its presynaptic actions have not been addressed yet. Here, we postulate that GHSR1a regulates presynaptic voltage-gated calcium channels (VGCC), the structure that controls neurotransmitter release. We performed patch clamp recordings and imaging analysis in HEK293t cells transiently transfected with GHSR1a or GHSR1a-A204E (mutant lacking constitutive activity), and CaV2.1 or CaV2.2 and its auxiliary subunits. We found that GHSR1a constitutive activity inhibits CaV2.1 and CaV2.2 currents. We also observed that GHSR1a constitutive activity acts through a Gαi/o voltage independent mechanism. On the other hand, we observed that GHSR1a ghrelin-evoked activity inhibits CaV2.1 and CaV2.2 by a different pathway that depends on Gαq, Gβγ, and it is CaVβ subtype-dependent. Moreover, imaging analysis showed that GHSR1a constitutive activity impaired VGCC density at the plasma membrane, likely by reducing its traffic. Our results demonstrated that constitutive and ghrelin-evoked GHSR1a activities inhibit presynaptic calcium channels utilizing different pathways.