Plays a role in cardiac repolarization possibly by stabilizing membrane expression of the potassium channel KCNH2/HERG, or by assisting its synthesis, folding or export from the endoplasmic reticulum, in a heat shock protein-dependent manner. Interacts with the core-glycosylated, but not the fully glycosylated form of KCNH2/HERG. Interacts with DNAJA1 and HSPA8. Interacts (via the C-terminus) with HSPA1A; this interaction additively increases KCNH2 expression. Probably located in the endoplasmic reticulum and/or possibly the cis-Golgi apparatus.