2-Aminoethoxydiphenyl borate (2-APB) stimulates a conformationally coupled calcium release pathway in the NG115-401L neuronal cell line

We report in this study a 2-aminoethoxydiphenyl borate (2-APB) activated Ca2+ pathway in NG115-401L (401L) neuronal cells bearing resemblance to hormonal and ryanodine receptor activated pathways. We observed that 2-APB, in contrast to much earlier work, did not inhibit store operated Ca2+ channel (SOC) function, but rather induced potent Ca2+ discharge responses that robustly activated SOC-mediated Ca2+ influx. Further, these studies intriguingly revealed that the 2-APB-induced Ca2+ release pathway likely couples conformationally to targets in the plasma membrane, as membrane permeabilization or actin perturbation abolished the ability of the compound to stimulate Ca2+ signals. These findings suggest that conformationally sensitive complexes form between endoplasmic reticulum and plasma membrane components that not only regulate Ca2+ influx, previously proposed as the conformational coupling hypothesis, but are also required to promote Ca2+ release from intracellular stores. These observations further characterize the 401L neuronal cell line as having unique characteristics that may prove useful in gaining insight into the nature of the coupling mechanism linking Ca2+ release to Ca2+ influx.