GHSR1a constitutive activity decreases presynaptic voltage-gated calcium channels level in plasma membrane

AGOSTI F; LOPEZ SOTO EJ; MARTINEZ DAMONTE V; GANDINI, A; RODRIGUEZ S; MARIE J; VIGNES M; FELIX R; RAINGO J

Huerta Grande, Córdoba

Congreso; XXIX Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2014

Sociedad Argentina de Investigación en Neurociencia

Growth Hormone Secretagogue Receptor type 1a (GHSR1a) is the G protein-coupled receptor that has the highest constitutive activity known (around 50% of the maximum activity induced by its endogenous ligand, ghrelin). GHSR1a is highly expressed at appetite controlling brain nuclei where it mediates ghrelin orexigenic effects. The physiological effect of its constitutive activity remains largely unknown. We study how this constitutive activity impacts on presynaptic voltage-operated calcium channels (VOCC). We co-transfected HEK cells with the GHSR1a or a mutant without constitutive activity (GHSR1aA204E) and the presynaptic VOCC (CaV2.1 or CaV2.2), and we assayed VOCC expression levels by imaging and western blot. We found that constitutive activity decreases protein amount of the VOCC at the plasma membrane. Also when we incubated HEK cells expressing GHSR1a and CaV2.1 or CaV2.2 with Substance P Analog (GHSR1a inverse agonist) we detected the same VOCC level at the plasma membrane than when GHSR1aA204E is co-expressed with the VOCC. We are now interested in the intracellular mechanism implicated in GHSR1a constitutive activity. Regarding to this issue, we have found that the receptor signals via a Gi/o cascade since pre-incubation with Pertussis Toxin restores VOCC protein amount at the plasma membrane. We propose that GHSR1a constitutive activity can affect synapse activity by decreasing the availability of presynaptic VOCC at the plasma membrane of the presynaptic terminal.