Kvβ2 inhibits the Kvβ1-mediated inactivation of K ⁺ channels in transfected mammalian cells

Cloned auxiliary β-subunits (e.g. Kvβ1) modulate the kinetic properties of the pore-forming α-subunits of a subset of shaker-like potassium channels. Coexpression of the α-subunit and Kvβ2, however, induces little change in channel properties. Since more than one β-subunit has been found in individual K ⁺ channel complexes and expression patterns of different β-subunits overlap in vivo, it is important to test the possible physical and/or functional interaction(s) between different β-subunits. In this report, we show that both Kvβ2 and Kvβ1 recognize the same region on the pore-forming α-subunits of the Kv1 Shaker-like potassium channels. In the absence of α-subunits the Kvβ2 polypeptide interacts with additional β-subunit(s) to form either a homomultimer with Kvβ2 or a heteromultimer with Kvβ1. When coexpressing α-subunits and Kvβ1 in the presence of Kvβ2, we find that Kvβ2 is capable of inhibiting the Kvβ1-mediated inactivation. Using deletion analysis, we have localized the minimal interaction region that is sufficient for Kvβ2 to associate with both α-subunits and Kvβ1. This mapped minimal interaction region is necessary and sufficient for inhibiting the Kvβ1-mediated inactivation, consistent with the notion that the inhibitory activity of Kvβ2 results from the coassembly of Kvβ2 with compatible α-subunits and possibly with Kvβ1. Together, these results provide biochemical evidence that Kvβ2 may profoundly alter the inactivation activity of another β-subunit by either differential subunit assembly or by competing for binding sites on α-subunits, which indicates that Kvβ2 is capable of serving as an important determinant in regulating the kinetic properties of K ⁺ currents.