1.H.1.1.11
Claudin 2 (Claudin-2; CLDN2) (forms narrow, fluid filled, water-permeable cation-selective paracellular pores) (Angelow et al., 2008; Yu et al., 2009).  It is a dimer in a high molecular weight protein complex (Van Itallie et al. 2011; Krug et al. 2014). Transports Na⁺, K⁺, Ca²⁺ smal organic molecules and water through the paracellular channel (Fromm et al. 2017). Site-specific distributions of claudin-2- and claudin-15-based paracellular channels drive their organ-specific functions in the liver, kidney, and intestine (Tanaka et al. 2017). Disruption of the gastrointestinal epithelial barrier is a hallmark of chronic inflammatory bowel diseases (IBDs), and in the intestines of patients with IBDs, the expression of CLDN2 is upregulated (Takigawa et al. 2017). Leu increases Ca²⁺ flux through cellular redistribution of Cldn-2 to the tight junction membrane (Gaffney-Stomberg et al. 2018).