2APB

2-Aminoethoxydiphenyl borate, commonly abbreviated as 2-APB, is an organic compound used as a pharmacological tool to study intracellular calcium signaling. It is a borate ester derived from diphenyl borate with an aminoethoxy substituent and is typically used in cellular experiments to modulate calcium currents and stores.

The primary actions of 2-APB are to inhibit IP3 receptor–mediated calcium release from the endoplasmic reticulum and to block store-operated calcium entry through the STIM1–Orai1 pathway. By limiting IP3-induced calcium release and reducing sustained calcium influx, 2-APB helps researchers investigate the roles of IP3 receptors and store-operated calcium entry in various cellular processes. Its effects are highly concentration- and context-dependent, and the compound can interact with multiple ion channels and signaling proteins beyond IP3 receptors, leading to varying outcomes across cell types and experimental setups.

Because of its broad and context-dependent actions, 2-APB is considered a tool rather than a highly selective drug. Experimental results obtained with 2-APB should be interpreted with caution and, when possible, validated with complementary approaches such as genetic manipulation of IP3 receptors or store-operated calcium entry components, or with more selective modulators.

In practice, 2-APB is used in physiology and neuroscience research to dissect calcium signaling pathways, monitor changes with calcium imaging, and accompany electrophysiological studies. Stock solutions are typically prepared in DMSO, and working concentrations commonly span the low to mid micromolar range, with careful controls to account for off-target effects.