Indeed, in instances where BAG3 mutations do induce protein aggregates and provoke cardiomyopathy, the mutant BAG3 protein acquires a gain-of-function aggregate-prone state, which forms protein aggregates with Hsp70, its natural binding partner and Hsp70 clients (Meister-Broekema et al., 2018). Here, BAG3 is linked to cardiomyopathy.