Dynamic Localization of Glucokinase and Its Regulatory Protein in Hypothalamic Tanycytes

SALGADO, MAGDIEL; Tarifeño-Saldivia, Estefanía; Ordenes, Patricio; Millán, Carola; Yañez, María José; Llanos, Paula; Villagra, Marcos; Elizondo?Vega, Roberto; Martínez, Fernando; Nualart, Francisco; Uribe, Elena; de los Angeles García-Robles, María; Chowen, Julie A.


Glucokinase (GK), the hexokinase involved in glucose sensing in pancreatic beta cells, is also expressed in hypothalamic tanycytes, which cover the ventricular walls of the basal hypothalamus and are implicated in an indirect control of neuronal activity by glucose. Previously, we demonstrated that GK was preferentially localized in tanycyte nuclei in euglycemic rats, which has been reported in hepatocytes and is suggestive of the presence of the GK regulatory protein, GKRP. In the present study, GK intracellular localization in hypothalamic and hepatic tissues of the same rats under several glycemic conditions was compared using confocal microscopy and Western blot analysis. In the hypothalamus, increased GK nuclear localization was observed in hyperglycemic conditions; however, it was primarily localized in the cytoplasm in hepatic tissue under the same conditions. Both GK and GKRP were next cloned from primary cultures of tanycytes. Expression of GK by Escherichia coli revealed a functional cooperative protein with a S-0.5 of 10 mM. GKRP, expressed in Saccharomyces cerevisiae, inhibited GK activity in vitro with a K-i 0.2 mu M. We also demonstrated increased nuclear reactivity of both GK and GKRP in response to high glucose concentrations in tanycyte cultures. These data were confirmed using Western blot analysis of nuclear extracts. Results indicate that GK undergoes short-term regulation by nuclear compartmentalization. Thus, in tanycytes, GK can act as a molecular switch to arrest cellular responses to increased glucose.

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Título según WOS: Dynamic Localization of Glucokinase and Its Regulatory Protein in Hypothalamic Tanycytes
Título según SCOPUS: Dynamic localization of glucokinase and its regulatory protein in hypothalamic tanycytes
Título de la Revista: PLOS ONE
Volumen: 9
Número: 4
Fecha de publicación: 2014
Página de inicio: e94035
Idioma: English
URL: http://dx.plos.org/10.1371/journal.pone.0094035