KCNH2 and myocardial ischemia: In addition, the hERG/IKr channel was selectively cleaved by serine proteases, such as proteinase K (PK) in the S5-pore linker of the hERG, and calpain-1, which is upregulated in cardiac ischemia, and in the Gly-603 in the S5-pore linker of the hERG [38].