KCNJ4 and idiopathic pulmonary fibrosis: Although there is currently no direct evidence indicating an interaction between HRK1 and IPF, its homolog protein KCNJ2 is significantly increased in the fibroblasts and bronchoalveolar lavage fluid of IPF patients and has been used as a biomarker for the differential diagnosis of IPF and other interstitial lung diseases [66].