How Azobenzene Photoswitches Restore Visual Responses to the Blind Retina

Abstract

Summary Azobenzene photoswitches confer light sensitivity onto retinal ganglion cells (RGCs) in blind mice, making these compounds promising candidates as vision-restoring drugs in humans with degenerative blindness. Remarkably, photosensitization manifests only in animals with photoreceptor degeneration and is absent from those with intact rods and cones. Here we show that P2X receptors mediate the entry of photoswitches into RGCs where they associate with voltage-gated ion channels, enabling light to control action potential firing. All charged photoswitch compounds require permeation through P2X receptors, whose gene expression is upregulated in the blind retina. Photoswitches and membrane-impermeant fluorescent dyes likewise penetrate through P2X receptors to label a subset of RGCs in the degenerated retina. Electrophysiological recordings and mapping of fluorescently-labeled RGC dendritic projections together indicate that photosensitization is highly selective for OFF-RGCs. Hence P2X receptors are a natural conduit allowing cell type-selective and degeneration-specific delivery of photoswitches to restore visual function in blinding disease.

On the permeation of large organic cations through the pore of ATP-gated P2X receptors

“…This finding has considerable physiological significance because it discloses an unsuspected role of polyamines in P2X signaling and more generally because it raises the possibility that activation of P2X receptors may allow for the exchange of other physiological molecules between cells, such as amino acids. Notably, a recent study exploited the large-pore property of P2X receptors to deliver small membrane-impermeable drugs to diseased retina cells (42). We thus propose that besides the critical role of the permeation of inorganic cations, the passage of small-sized metabolites, like spermidine, through the ATPgated open P2X pore may contribute to alternative physiological responses.…”

Sulfonated Pyrene as a Photoregulator for Single‐Stranded DNA Looping

“…Following this pioneering work, Asanuma, Komiyama, and co‐workers reported the control of DNA or RNA hybridization and gene expression by using azobenzene as a molecular photoswitch . The utility of azobenzenes for photoregulating the conformation and function of peptides and proteins, photocontrolling ion channels, and photorestoring human vision have also been reported . The main reasons for the wide use of azobenzenes as photoswitches in biological applications are their easy synthesis, relatively high photostationary states and quantum yields, fast photoisomerization, and low rate of photobleaching .…”

Molecular mechanism underlying the subtype-selectivity of competitive inhibitor NF110 and its distinct potencies in human and rat P2X3 receptors

“…P2X7 is involved in inflammation, immune regulation, and neurological and muscu-loskeletal diseases [18][19][20]; and multiple P2X7-targeting molecules, such as AZD9056, GSK1482160, CE-224/535, and JNJ-54175446, went into clinical researches for the treatments of rheumatoid arthritis, inflammatory pain and other diseases [15,[21][22][23]. Meanwhile, DENAQ, a small molecule permeable for the P2X7 receptor, was used to treat retinitis pigmentosa and agerelated macular degeneration [24]. Noteworthy, nearly all of compounds that are in the clinical researches, like AF-219, AF-130, NC-2600, AZD9056 and GSK1482160, exhibit high-selectivity on certain subtype of P2X receptors [15,21,25,26].…”