Aquaporins: Water channels that maintain ocular health

May 2 - Fort Lauderdale, FL - Aquaporins are the water channels, the body's plumbing system, that move water across the biological compartment and without which life would cease, according to Peter Agre, MD, of Johns Hopkins University, Baltimore, who delivered the second keynote address at the ARVO annual meeting.

When Dr. Agre, the 2003 recipient of the Nobel Prize in chemistry, and colleagues discovered aquaporin-1, they suspected that bilayer diffusion was insufficient to carry out the work needed to maintain stability in the body; selective water channels must exist that at the same time allow movement of water but that block protons. Deficits in aquaporin-1 result in disease states, an extreme example of which is individuals with no detectable aquaporin in any tissue.

Aquaporin-1 is present in the lens epithelium, the corneal endothelium, non-pigmented epithelium (ciliary and iris), and the trabecular meshwork. Other members of the aquaporin family have also been identified-aquaporin-3 (conjunctiva), aquaporin-4 (perivascular membranes in glial cells, Muller cells), and aquaporin-5 (apical membrane), he explained.

"We don't know what the overall significance of the protein is in eye tissues," Dr Agre said. "Preliminary evaluation of our human aquaporin-1 failed to identify any profound phenotype in the eye tissue. I suspect that the protein is important in stress states after corneal injuries, for example, the ability to maintain corneal transparency. We know where the protein is, we know its structure, but we don't know what it is. There is still a lot of work to be done on aquaporin in the eye."