FXYD2 and chronic kidney disease: In addition, to the above overlapping protein precursors, two proteins including, APOA1 (a protein which is associated with renal dysfunction in HF patients27) and FXYD2 (a protein which mediates the function of the Na, K-ATPase in mammalian kidney epithelial cells28) are commonly identified in CRS and CKD, similarly reflecting the common underlying molecular profiles of these diseases.