Tight-junction protein required for paracellular chloride transport in the kidney (PubMed:20921420, PubMed:25831548). Mediates recruitment of CLDN4 to tight junction in the kidney (PubMed:20921420, PubMed:25831548). Claudins play a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. Directly interacts with TJP1/ZO-1, TJP2/ZO-2 and TJP3/ZO-3 (PubMed:10601346). Interacts with CLDN4 (PubMed:20921420). Interacts with KLHL3 (PubMed:25831548). Expressed primarily in lung and kidney (PubMed:9892664). Present in both cortical and medullar collecting ducts (at protein level) (PubMed:20921420). Ubiquitinated by the BCR(KLHL3) E3 ubiquitin ligase complex in the kidney, leading to its degradation. Conditional knockout mice lacking Cldn8 in the collecting duct of kidney show hypotension, hypokalemia, and metabolic alkalosis (PubMed:25831548). Belongs to the claudin family.