Outside the mainstream: novel collecting duct proteins regulating water balance

Abstract

Body water balance is critical to survival and, therefore, very tightly regulated by the hypothalamus and kidney. A key mechanism involved in this process, the arginine vasopressin-mediated phosphorylation and apical membrane insertion of aquaporin 2 in the collecting duct, has been extensively studied; however, with the increased availability of conditional knockout animals, several novel collecting duct proteins have recently been implicated in water homeostasis. In this Mini-Review, we briefly discuss these novel proteins and their roles in the regulation of water homeostasis.

Keywords: aquaporin 2; collecting duct; water homeostasis.

Fig. 1.

Novel proteins implicated in water balance in the kidney collecting duct outside of the linear AVP-AQP2 axis. These proteins are localized in different cellular compartments and have a diverse range of functions, such as cell-to-cell adhesion, formation of epithelial polarity (13, 28), transduction of cellular signals (10, 38), recycling of channels/transporters to and from the plasma membrane (23), generation of metabolites (7, 14, 15, 33), posttranslational modifications (as shown by star) of channels/transporters, and transcriptional regulation (16). Proteins specifically discussed in this Mini-Review are highlighted in bold. Abbreviations: AKAP220, A-kinase anchoring protein 220; GATA2, GATA binding protein 2; MPGES-1, microsomal prostaglandin E synthase 1; NFAT5, nuclear factor of activated T cells 5; RhoA, Ras homolog gene family member A; TAZ, transcriptional co-activator with PDZ binding motif.