IMBICE   05372
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA CELULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
PROTEOLYTIC FRAGMENTS OF GHRELIN N-TERMINUS SHOW DIFFERENTIAL OREXIGENIC EFFECTS THAN THE PARENTAL HORMONE
Autor/es:
ANTONELA FITTIPALDI; NICOLAS DE FRANCESCO; GIMENA FERNANDEZ; SEBASTIAN TREJO; DANIELA LUFRANO; DANIEL CASTROGIOVANNI; MARIO PERELLO
Lugar:
Salta
Reunión:
Congreso; LV Congreso de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2019
Institución organizadora:
Sociedad Argentina de Investigación Bioquímica y Biología Molecular
Resumen:
The stomach-derived hormone ghrelin was first reported as a growth hormone secretagogue and a ?hunger? hormone that stimulates food intake and the preference for energy-dense foods. However since its discovery in 1999, the number and kind of activities reported for ghrelin has been increasing over time, including gut motility and gastric secretion/emptying, regulation of adiposity, blood glucose levels, bone metabolism, sleep, stress and hedonic feeding, enhancement of contractility and vasodilatation. Ghrelin is a peptide of 28 residues acylated with an octanoic acid at Ser3. The N-terminal sequence of ghrelin along with the octanoyl group are essential to act on the ghrelin receptor (GHSR1a) through which the hormone triggers its effects. As many peptide hormones undergo proteolytic processing as a regulatory mechanism?producing fragments that may differ not only in the magnitude of the effects but also the type of bioactivity they exert?here, we explored the hypothesis that circulating ghrelin can be cleaved in order to generate ghrelin-derived peptides with differential bioactivities. Initially, by in vitro digestion of ghrelin with human plasma followed by MALDI-TOF MS detection, we found that the bonds of ghrelin sequence extended from residue 11 to 16, are hydrolyzed by proteases present in plasma. Then, we also incubated ghrelin with a human hepatocarcinoma cell line (HepG2) or with the extracellular medium of a 48h-culture of these cells. The MALDI-TOF MS analysis of these digests showed the same ?hot cleavage zone? in ghrelin sequence previously found with plasma digestion samples. In addition, using a fluorescent analogue of ghrelin, extracellular medium as source of proteases and different proteases inhibitors, we have been able to elucidate that HepG2 cells secrete, at least, two different proteases able to cleave ghrelin peptide bonds. In order to evaluate the impact of proteolysis on the orexigenic effects of ghrelin, we tested one of the ghrelin-derived fragments detected in MALDI-TOF MS analysis of in vitro digests (ghrelin(1-14)). Despite having the active core of the hormone, we found that ghrelin(1-14) failed to induce neuronal activation, assessed by the marker of neuronal activation c-Fos, nor to increase food intake in mice. Additionally, these ghrelin-derived peptide was unable to impair the orexigenic effect of full-length ghrelin in competition assays. Together, these data support the existence of a proteolytic extracellular mechanism that generates ghrelin-derived peptides with different bioactivity than full-length ghrelin. Moreover, the liver may be involved in this mechanism during the passage of ghrelin through the hepatic portal circulation.