Identification that ADAM17 mediates proteolytic maturation of calcium channel auxiliary α2δ subunits, and enables calcium current enhancement
The auxiliary 2{delta} subunits of voltage-gated calcium (CaV) channels are key to augmenting expression and function of CaV1 and CaV2 channels, and are also important drug targets in several therapeutic areas, including neuropathic pain. The 2{delta} proteins are translated as pre-proteins encoding both 2 and {delta}, and post-translationally proteolysed into 2 and {delta} subunits, which remain associated as a complex. In this study we have identified ADAM17 as a key protease involved in proteolytic processing of pro-2{delta}-1 and 2{delta}-3 subunits. We provide three lines of evidence: firstly, proteolytic cleavage is inhibited by chemical inhibitors of particular metalloproteases, including ADAM17. Secondly, proteolytic cleavage of both 2{delta}-1 and 2{delta}-3 is markedly reduced in cell lines by knockout of ADAM17 but not ADAM10. Thirdly, proteolytic cleavage is reduced by the N-terminal active domain of TIMP-3 (N-TIMP-3), which selectively inhibits ADAM17. We have found previously that proteolytic cleavage into mature 2{delta} is essential for the enhancement of CaV function, and in agreement, knockout of ADAM17 inhibited the ability of 2{delta}-1 to enhance both CaV2.2 and CaV1.2 calcium currents. Thus, our study identifies ADAM17 as a key protease required for proteolytic maturation of 2{delta}-1 and 2{delta}-3, and thus a potential drug target in neuropathic pain.