Block of Specific Gap Junction Channel Subtypes by 2-Aminoethoxydiphenyl Borate (2-APB)

Abstract

2-Aminoethoxydiphenyl borate (2-APB), an inositol 1,4,5-triphosphate receptor modulator, inhibits capacitive current transients measured in normal rat kidney and human embryonic kidney 293 cells, an indication of blocking gap junction channels between these cells. Here, we used the dual whole-cell patch-clamp method to study the actions of 2-APB on gap junction channels formed by selected connexins expressed in a communication-deficient neuroblastoma cell line (N2A). 2-APB dose-dependently and reversibly blocked junctional currents of connexin (Cx) 50 gap junction channels. The concentrationinhibition curve of 2-APB on the junctional current indicated an IC 50 of 3.7 M, lower than that of most gap junction inhibitors. At a concentration of 20 M, 2-APB also significantly blocked junctional conductance in cell pairs coupled by Cx26, Cx30, Cx36, Cx40, and Cx45 but did not appreciably affect coupling in cell pairs expressing Cx32, Cx43, and Cx46. Although concentration inhibition curves of 2-APB on Cx36 channels were similar to Cx50 (Cx36; IC 50 , 3.0 M), IC 50 values were higher for Cx43 (51.6 M), Cx45 (18

Screening of gap junction antagonists on dye coupling in the rabbit retina

“…In contrast, some specificity against different connexins has previously been reported for mefloquine, 2-APB and quinine (Srinivas et al, 2001;Cruikshank et al, 2004;Bai et al, 2006). For example, mefloquine preferentially blocked Cx36 and Cx50 gap junctions compared to Cx26, Cx32, Cx43, and Cx46 gap junctions (Srinivas et al, 2001).…”

2-Aminoethyl diphenyl borinate (2-APB) inhibits TRPM7 channels through an intracellular acidification mechanism

“…[3][4][5][6][7][8] During the last decade, effects of 2-APB on numerous other ion transport proteins have been described. For example, 2-APB is an inhibitor of sarcoplasmic-endoplasmic reticulum Ca 2+ -ATPase (SERCA) pumps, 9 gap junction connexins, 10 potassium channels 11 and volume-regulated anion channels 12 at micromolar concentrations. Members of the Transient Receptor Potential (TRP) family of cation channels were also shown to be sensitive to this compound.…”

“…The primary effect at the single-channel level is a reduced probability of opening without significant reduction in unitary conductance. 10 Importantly, the differential sensitivity of various connexins to 2-APB was shown to be unrelated to their sensitivity to pH. 10,38 As for TRPM7 and TRPC5, 2-APB blocks connexins only from the extracellular side of the membrane.…”

“…10 Importantly, the differential sensitivity of various connexins to 2-APB was shown to be unrelated to their sensitivity to pH. 10,38 As for TRPM7 and TRPC5, 2-APB blocks connexins only from the extracellular side of the membrane. 39 2-APB block of SERCA pumps is isoform-specific, as it is for connexins, and involves decreased affinity for Ca 2+ and diminished phosphoryl transfer from ATP.…”

The Effects of 2-Aminoethoxydiphenyl Borate and Diphenylboronic Anhydride on Gap Junctions Composed of Connexin43 in TM4 Sertoli Cells

“…For example, using reconstituted Cx hemichannels obtained from native tissues and stably-transfected cells, we characterized the direct inhibitions of Cx26 and/or Cx32 channels by 2-APB and DPBA. 26) Some studies also implicated a reduction in junctional channel open probability induced by 2-APB through inhibition of electrical communication 49) or through a direct extracellular action on Cxs. 50) Thus a comparative analysis among the tested compounds to find the pharmacophore for Cx43 channel inhibition is necessary.…”