Ion channel expression in PMA-differentiated human THP-1 macrophages.
J Membr Biol
; 152(2): 141-57, 1996 Jul.
Article
en En
| MEDLINE
| ID: mdl-9139125
ABSTRACT
Ion channel expression was studied in THP-1 human monocytic leukemia cells induced to differentiate into macrophage-like cells by exposure to the phorbol ester, phorbol 12-myristate 13-acetate (PMA). Inactivating delayed rectifier K+ currents, IDR, present in almost all undifferentiated THP-1 monocytes, were absent from PMA-differentiated macrophages. Two K+ channels were observed in THP-1 cells only after differentiation into macrophages, an inwardly rectifying K+ channel (IIR) and a Ca2+-activated maxi-K channel (IBK). IIR was a classical inward rectifier, conducting large inward currents negative to EK and very small outward currents. IIR was blocked in a voltage-dependent manner by Cs+, Na+, and Ba2+, block increasing with hyperpolarization. Block by Na+ and Ba2+ was time-dependent, whereas Cs+ block was too fast to resolve. Rb+ was sparingly permeant. In cell-attached patches with high [K+] in the pipette, the single IIR channel conductance was approximately 30 pS and no outward current could be detected. IBK channels were observed in cell-attached or inside-out patches and in whole-cell configuration. In cell-attached patches the conductance was approximately 200-250 pS and at potentials positive to approximately 100 mV a negative slope conductance of the unitary current was observed, suggesting block by intracellular Na+. IBK was activated at large positive potentials in cell-attached patches; in inside-out patches the voltage-activation relationship was shifted to more negative potentials by increased [Ca2+]. Macroscopic IBK was blocked by external TEA+ with half block at 0.35 mM. THP-1 cells were found to contain mRNA for Kv1.3 and IRK1. Levels of mRNA coding for these K+ channels were studied by competitive PCR (polymerase chain reaction), and were found to change upon differentiation in the same direction as did channel expression IRK1 mRNA increased at least 5-fold, and Kv1.3 mRNA decreased on average 7-fold. Possible functional correlates of the changes in ion channel expression during differentiation of THP-1 cells are discussed.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Acetato de Tetradecanoilforbol
/
Monocitos
/
Regulación Neoplásica de la Expresión Génica
/
Canales de Potasio Calcio-Activados
/
Canales de Potasio de Rectificación Interna
/
Canales de Potasio con Entrada de Voltaje
/
Canales Iónicos
/
Macrófagos
/
Proteínas de Neoplasias
Límite:
Humans
Idioma:
En
Revista:
J Membr Biol
Año:
1996
Tipo del documento:
Article
País de afiliación:
Estados Unidos