1.A.8.8.9
Aquaporin 5 (x-ray structure at 2.0 Å resolution (PDB# 3D9S) is available) (Horsefield et al., 2008). Aqp5 is a marker for proliferation and migration of human breast cancer cells (Jung et al., 2011). Plays a role in chronic obstructive pulmonary diseases (COPD) (Zhao et al. 2014).  Its expression is regulated by androgens (Pust et al. 2015). As in humans, the chicken ortholog, Aqp5, is found in the intestine, the jejunum, ileum and colon (Ramírez-Lorca et al. 2006). Proteomic analyses of the ocular lens revealed palmitoylation (Wang and Schey 2018). Aquaporin 5 expression correlates with tumor multiplicity and vascular invasion in hepatocellular carcinoma (Vireak et al. 2019). The ability of Aqp5 (as well as Aqp0 and Aqp1) to transport hydrogen peroxide (H₂O₂) may cause cataracts in the eye (Varadaraj and Kumari 2020). AQP3 and AQP5 play important but different roles in spermatogenesis and sperm maturation in dogs (Mirabella et al. 2021). The up-regulation of AQP1, AQP3 and AQP5 in skin during summer season indicates roles in thermoregulation (Debbarma et al. 2020). Aqp5 interacts with TRPV4 (see 1.A.4.2.5 for the rat ortholog) (Kemény and Ducza 2022). AQP5 facilitates osmotically driven water flux across biological membranes as well as the movement of hydrogen peroxide and CO₂. Various mechanisms dynamically regulate AQP5 expression, trafficking, and function. Besides fulfilling its primary water permeability function, AQP5 regulates downstream effectors (D'Agostino et al. 2023). Modulation of membrane trafficking of AQP5 in the lens in response to changes in zonular tension is mediated by TRPV1 (Petrova et al. 2023).Methazolamide reduces AQP5 mRNA expression and immune cell migration, and may be a drug for sepsis therapy (Rump et al. 2024). Aqp5 interacts with Ezrin (see 8.A.25.1.1).