HYPOTHALAMIC TANYCYTES INTERNALIZE GHRELIN IN THEIR SOMA AND VECTORIALLY TRANSPORT TO THE ENDFEET

IVANA M. GÓMEZ; DANIEL CASTROGIOVANNI; MAIA URIARTE; MARIO PERELLÓ; PABLO NICOLÁS DE FRANCESCO

Buenos Aires

Encuentro; Primer Encuentro del Club de la Glía Cono Sur; 2022

Club de la Glía - Cono Sur

Hypothalamic tanycytes are polarized glial cells that line the base of the third ventricle. Their somas contact the cerebrospinal fluid (CSF), whereas their terminal side (endfeet) contact the capillaries of the blood-brain barrier or the fenestrated capillaries of the median eminence, forming an anatomical interface for the transport of molecules between blood and CSF. Using mice and rats, we recently described that tanycytes internalize the orexigenic hormone ghrelin in vivo and in vitro. Here, we study the cellular mechanisms mediating ghrelin uptake in hypothalamic tanycytes and its transport direction. Specifically, we incubated primary cultures of rat tanycytes with a fluorescent ghrelin variant (Fr-ghrelin) in basal conditions or after pharmacological blockage of either clathrin-mediated internalization using Pitstop or Dyngo4a, or intracellular transport using colchicine. We also coincubated tanycytes with Fr-ghrelin and either native ghrelin or desacyl-ghrelin. We then quantified fluorescence intensity in soma, process and endfeet of each cell. We found that intracellular fluorescence: 1) is found predominantly in the soma of tanycytes after a 5-min incubation; 2) increased in somas, processes and endfeet after 30-min incubation as compared to 5-min incubation; 3) was reduced only in terminals in the presence of colchicin; 4) was decreased in all compartments in the presence of Pitstop and Dyngo4a; 5) was reduced in somas, processes and endfeet after coincubation with native ghrelin or desacyl-ghrelin. This evidence shows that tanycytes can specifically internalize ghrelin through clathrin-mediated endocytosis in the somas and presumably transport it from the apical to the terminal side.