The Role of Aquaporins in Ocular Lens Homeostasis

Abstract

Aquaporins (AQPs), by playing essential roles in the maintenance of ocular lens homeostasis, contribute to the establishment and maintenance of the overall optical properties of the lens over many decades of life. Three aquaporins, AQP0, AQP1 and AQP5, each with distinctly different functional properties, are abundantly and differentially expressed in the different regions of the ocular lens. Furthermore, the diversity of AQP functionality is increased in the absence of protein turnover by age-related modifications to lens AQPs that are proposed to alter AQP function in the different regions of the lens. These regional differences in AQP functionality are proposed to contribute to the generation and directionality of the lens internal microcirculation; a system of circulating ionic and fluid fluxes that delivers nutrients to and removes wastes from the lens faster than could be achieved by passive diffusion alone. In this review, we present how regional differences in lens AQP isoforms potentially contribute to this microcirculation system by highlighting current areas of investigation and emphasizing areas where future work is required.

Dexmedetomidine and Tear Production: Evaluation in Dogs as Spontaneous Model for Ocular Surface Disorders

“…Recently, ophthalmic research has been focused on aquaporins (AQPs), a family of water channel proteins that controls osmotically driven water and fluid transport across cell membranes. The authors underlined the following functional roles of AQPs in the eye function: water balance maintenance to ensure transparency in cornea and lens, aqueous humor production, corneal wound healing and regulation of the tear film osmolarity and retinal homeostasis [ 3 , 4 , 5 ].…”

A comprehensive spatial-temporal transcriptomic analysis of differentiating nascent mouse lens epithelial and fiber cells

“…Lens fiber cell elongation extends the original lens length by a factor of 1,000-fold (Audette et al, 2017; Bassnett and Costello, 2017), while their cytoplasmic compartments accumulate crystallin proteins (Cvekl and Zhang, 2017). The lens fibers form an elaborate cytoskeletal and membrane organization to support lens transparency (Beyer and Berthoud, 2014; Dahm et al, 2011; Mathias et al, 2010; Schey et al, 2017; Song et al, 2009; Wang et al, 2016).…”

Deletion of Seventeen Amino Acids at the C-Terminal End of Aquaporin 0 Causes Distortion Aberration and Cataract in the Lenses of AQP0ΔC/ΔCMice

“…Protein hydropathy and crystallography analyses envisage six transmembrane domains and cytoplasmic N- and C-terminal domains for the AQP superfamily. In AQP0, the C-terminus modulates water permeability35,36; it binds to cytoskeletal proteins to ensure proper fiber cell alignment 37–40. Several posttranslational modifications (PTMs), such as phosphorylation, deamidation, and isomerization occur at this domain 40.…”