PCSK9 and familial hypercholesterolemia: In addition, and unrelated to the ZHX-ANGPTL4 pathway, another recent study has shown that hypercholesterolemia of nephrotic syndrome is initiated by the secretion of PCSK9 from cortical collecting duct cells, where PCSK9 is a chaperone protein for the epithelial sodium channel (ENaC) (11).