Genistein and tyrphostin AG556 decrease ultra‐rapidly activating delayed rectifier K⁺ current of human atria by inhibiting EGF receptor tyrosine kinase

Abstract

BACKGROUND AND PURPOSEThe ultra-rapidly activating delayed rectifier K + current I Kur (encoded by K v 1.5 or KCNA5) plays an important role in human atrial repolarization. The present study investigates the regulation of this current by protein tyrosine kinases (PTKs). EXPERIMENTAL APPROACHWhole-cell patch voltage clamp technique and immunoprecipitation and Western blotting analysis were used to investigate whether the PTK inhibitors genistein, tyrphostin AG556 (AG556) and PP2 regulate human atrial I Kur and hKv1.5 channels stably expressed in HEK 293 cells. KEY RESULTSHuman atrial I Kur was decreased by genistein (a broad-spectrum PTK inhibitor) and AG556 (a highly selective EGFR TK inhibitor) in a concentration-dependent manner. Inhibition of I Kur induced by 30 μM genistein or 10 μM AG556 was significantly reversed by 1 mM orthovanadate (a protein tyrosine phosphatase inhibitor). Similar results were observed in HEK 293 cells stably expressing hK v 1.5 channels. On the other hand, the Src family kinase inhibitor PP2 (1 μM) slightly enhanced I Kur and hK v 1.5 current, and the current increase was also reversed by orthovanadate. Immunoprecipitation and Western blotting analysis showed that genistein, AG556, and PP2 decreased tyrosine phosphorylation of hK v 1.5 channels and that the decrease was countered by orthovanadate. CONCLUSION AND IMPLICATIONSThe PTK inhibitors genistein and AG556 decrease human atrial I Kur and cloned hK v 1.5 channels by inhibiting EGFR TK, whereas the Src kinase inhibitor PP2 increases I Kur and hK v 1.5 current. These results imply that EGFR TK and the soluble Src kinases may have opposite effects on human atrial I Kur .Abbreviations EGFR, EGF receptor; I Kur , ultra-rapidly activating delayed rectifier potassium current; PP2, 3-(4-chlorophenyl) 1-(1,1-dimethylethyl)-1H-pyrazolo [3,4-d] pyrimidin-4-amine; PTK, protein tyrosine kinase; TK, protein kinase; tyrphostin AG556, AG556

Inhibition of esophageal-carcinoma cell proliferation by genistein via suppression of JAK1/2-STAT3 and AKT/MDM2/p53 signaling pathways

“…Genistein is a protein tyrosine kinase inhibitor [13,14]. Tyrosine phosphorylation activity was strikingly attenuated following treatment using genistein alone or in combination with the tyrosine kinase inhibitor AG556, leading to inhibition of ultrarapidly activating delayed rectifier K(+) current of human atria [15]. In addition, genistein increases the ratio of Bax to Bcl-2 by inducing P53 expression, promoting sensitivity to radiotherapy in esophageal cancer [16].…”

Noradrenaline up‐regulates volume‐regulated chloride current by PKA‐independent cAMP/exchange protein activated by cAMP pathway in human atrial myocytes

“…All patients were free from supraventricular tachyarrythmias, and the atria were grossly normal at the time of surgery. Human atrial myocytes were enzymically dissociated with the procedure described previously (Li et al, 2008;Xiao et al, 2017). Briefly, after excision, samples were quickly immersed in oxygenated, Ca 2+ -free cardioplegic solution for transport to the laboratory.…”

Cellular Uptake and Transport Mechanism of 6-Mercaptopurine Nanomedicines for Enhanced Oral Bioavailability

“…Genistein is an inhibitor of tyrosine-specific protein kinases (PTK) and inhibited the expression of caveolin-1 (cav-1). 41 The uptake of 6-MPNs showed no significant difference after intervening with Genistein.

Figure 3 Endocytosis and transport mechanism analysis of 6-MPNs in Caco-2 cells.

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