Protein phosphatase 2A reverses inhibiton of inward rectifying K+ currents by thyrotropin‐releasing hormone in GH3 pituitary cells

FEBS Letters

del Camino, Donato²  de la Peña, Pilar²  Barros, Francisco²  Mieskes, Gottfried¹ 

[1] Georg-August-Universität, Göttingen, Abt. Klinische Biochemie, Robert-Koch-Str. 40, D-3400 Göttingen, Germany;Departamento de Biología Funcional, Area de Bioquímica, Facultad de Medicina, Universidad de Oviedo, 33006 Oviedo, Spain

关键词: Thyrotropin-releasing hormone;    Inwardly rectifying K + current;    GH3 cell;    Protein phosphatase;    Anterior pituitary;    TRH;    thyrotropin-releasing hormone;    PP;    protein phosphatase;    PP3;    catalytic subunit of PP;    PK;    protein kinase;    ADP-NH-P;    adenosine 5'-(β;    γ-imino)triphosphate;    C.T.;    cholera toxin;   

DOI  :  10.1016/0014-5793(93)80851-K

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Thyrotropin-releasing hormone (TRH) reduces an inwardly rectifying K⁺ current in whole-cell voltage-clamped GH3 rat anterior pituitary cells. The TRH effect depends on the maintenance of a background level of Ca²⁺ in the pipette buffer, and is rapidly minimized by the intracellular dialysis produced under whole-cell conditions. Introduction of ADP-NH-P, a non-hydrolizable ATP analog, in the pipettes, nearly abolishes the TRH-evoked inhibition. The TRH-induced reduction of the inwardly rectifying current is significantly enhanced by incubation of cells 2–4 h with cholera toxin, but not by inclusion of 1 mM cyclic AMP in the pipettes. Under control whole-cell conditions, the reduction caused by TRH is not reversed upon washout of the neuropeptide. However, this effect is readily reversed by addition of purified catalytic subunits of protein phosphatase 2A (PP-2A_c) but not PP-1_c to the buffer used to fill the patch pipettes. Among previous results with PP inhibitors, these data indicate that PP2A is involved in the phosphorylation/dephosphorylation mechanism(s) that regulate the delayed TRH effects on GH₃ cell excitability.

【 授权许可】

Unknown