The function of CLDN4 (claudin 4, ENSG00000189143) is as follows. Can associate with other claudins to regulate tight junction structural and functional strand dynamics (PubMed:35773259, PubMed:36008380). May coassemble with CLDN8 into tight junction strands containing anion-selective channels that convey paracellular chloride permeability in renal collecting ducts (By similarity) (PubMed:36008380). May integrate into CLDN3 strands to modulate localized tight junction barrier properties (PubMed:35773259, PubMed:36008380). May disrupt strand assembly of channel-forming CLDN2 and CLDN15 and inhibit cation conductance (PubMed:35773259, PubMed:36008380). Cannot form tight junction strands on its own (PubMed:35773259, PubMed:36008380). {ECO:0000250|UniProtKB:O35054, ECO:0000269|PubMed:35773259, ECO:0000269|PubMed:36008380}.