Tanned: Ion channel clues to UV protection

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  • Published: Feb 1, 2013
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: Tanned: Ion channel clues to UV protection

Tanning solution

Transient receptor potential cation channel, subfamily A, member

Skin cells known as melanocytes can sense ultraviolet light and increase production of melanin - tanning - in the skin to protect themselves and the tissues below. New research reveals that a well-studied and chemically sensitive ion channel found in cells elsewhere in the body plays a central role in "detecting" incident ultraviolet.

Researchers at Brown University in Rhode Island, USA, demonstrated that melanocytes use a light-sensitive receptor to detect incident UV and to trigger melanin production and so putatively protect DNA from damage, although that was not demonstrated in the research itself. Now, members of the original team have homed in on an ion channel involved in the biomolecular chain of events, which could someday become a target for pharmaceuticals that boost the protective response in people with particular sensitivity to sunlight in terms of risk of developing skin damage or skin cancer.

Writing in the Proceedings of the National Academy of Sciences (USA), the team discusses the ion channel TRPA1 (transient receptor potential cation channel, subfamily A, member 1). This protein opens the floodgates allowing calcium ions to pour into the cells when they are exposed to ultraviolet light, specifically UVA in the 320 to 400 nanometres wavelength range. The increased cellular concentration of calcium ions signals the cell to begin production of the pigment melanin, which is involved in the purportedly shielding tanning response in humans. The degree to which tanning offers protection against incident UVA is limited, of course. Nevertheless, the work confirms that a phototransduction pathway chemical related to those found in the eye exists in the melanocyte response to UV.

Transient tale

Senior author Elena Oancea explains that their experiments show that TRPA1, which is known from a number of other sites in the body, is involved in an essential step in the skin's self-preserving response to potentially damaging UVA light. The finding strengthens the hypothesised link between the way in which the skin respond to UVA light and the way in which our eyes detect light. Oancea and co-author Nicholas Bellono add that this discovery regarding TRPA1 could open up the possibility of finding ways to boost melanin production artificially without exposure to UVA.

"It's exciting because it confirms this phototransduction pathway is similar to those found in the eye. It consists of a light-sensitive receptor, molecular signalling cascade, and an ion channel," Oancea explains. "The involvement of an ion channel makes this pathway a lot more like other phototransduction pathways."

Confessional science

Oancea confessed that she initially suspected another TRP ion channel might be the active agent. But numerous experiments led the team to TRPA1 as being involved in this process. Intriguingly, TRPA1 has also been demonstrated as allowing us to sniff out strong-smelling, but benign chemicals, such as those present in strongly flavoured foods. "TRPA1 ion channels are involved in the detection of pungent chemicals such as cinnamaldehyde, wasabi, and mustard oil, and we've now found it's important for this melanin response," Bellono adds.

Related Links

Proc Natl Acad Sci (USA), 2013, online: "UV light phototransduction activates transient receptor potential A1 ion channels in human melanocytes"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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