Aquaporin Expression In Ocular Tissuesindirect Evidence For A Role In Eye Physiology

Figure 1 summarizes the sites of fluid transport (panel A) and AQP protein expression (panel B) in the eye. Expression of AQP0 (MIP) in lens fiber has been known for many years, where its involvement in lens transparency and cataracts is well established. Mutations in AQP0 are associated with congenital cataracts in humans (10). However, the mechanisms by which AQP0 deficiency produces cataracts remain unknown. Aquaporin 1 is expressed strongly in endothelial cells and keratocytes in cornea, as well as in nonpigmented ciliary epithelium and in the epithelium at the anterior surface of the cornea. Aquaporin 3 is expressed throughout the corneal and conjunctival epithelium at the ocular surface. Aquaporin 5 is strongly expressed at the corneal epithelium as well. Aquaporin 4 is expressed in Müller cells in retina, and colocalizes with AQP1 in nonpigmented ciliary epithelium. The ocular expression pattern of AQPs provides indirect evidence for their possible involvement in intraocular pressure regulation (AQP1 and AQP4), corneal and lens transparency (AQP0, AQP1, and AQP5), visual signal transduction and retinal swelling following injury (AQP4), corneal and conjunctival barrier function (AQP3), and tear formation by lacrimal glands (AQP5). Our lab has generated transgenic mice individually lacking the major eye AQPs to establish their physiological functions. As described below, several predicted functions, such as involvement of AQP1

Fig. 1. Sites of water movement and aquaporin (AQP) expression in ocular tissues.

(A) Schematic showing physiological movements of water across various cell barriers in the eye.

(B) Sites of AQP protein expression in the eye.

Fig. 1. Sites of water movement and aquaporin (AQP) expression in ocular tissues.

(A) Schematic showing physiological movements of water across various cell barriers in the eye.

(B) Sites of AQP protein expression in the eye.

in aqueous fluid secretion, were confirmed, and a number of unexpected functions were discovered.

0 0

Post a comment