The present disclosure provides, inter alia, a recombinant engineered deubiquitinase (DUB) and methods for treating or ameliorating an inherited ion channelopathy, such as long QT syndrome, Brugada syndrome, or cystic fibrosis, in a subject. Further provided are methods for screening mutations causing such inherited ion channelopathies for a trafficking-deficient mutation that is treatable by the recombinant engineered DUB disclosed herein.