Professor Peter Hegemann from the Humboldt University in Berlin was co-awarded the 2013 Louis-Jeantet Prize for Medicine for the discovery of ion channels that can be activated by light and for launching a new discipline called optogenetics. Yesterday evening, the biochemist presented his research in a lecture about Channelrhodopsin: A small algal photoreceptor in service for optogenetics. He also answered a few questions about what triggered his passion for studying microscopic green alga.
Professor Hegemann, why is channelrhodopsin particularly interesting for optogenetics?
The ion channel fragment of the protein is small, easily expressed and it uses the ubiquitous endogenous retinal as chromophore, the part of a molecule responsible for its colour. Moreover, the rise of the photocurrent here is faster than in any other visual system.
Why did you get interested in studying microbial algae?
What triggered my interest was a paper in the journal Nature by the biophysicist Kenneth W. Foster who proposed that green alga use rhodopsin for behavioral light responses. His suggestion was based on action spectroscopy, a method to identify the type of molecule that absorbs active light.
When you first started working on green algae back in the 1980s, did you ever dream about using it to stimulate neurons in higher species in the distant future?
Not at all. Our interest was to understand rhodopsin-based signaling in this alga.
What other photoreceptors are you interested in?
We work on a diverse set of unusual photoreceptors. We have studied a light-activated adenylyl cyclase from the soil bacterium Beggiatoa that is also well suited for optogenetic applications. Other examples are the so-called histidine kinase rhodopsins and several melanopsins.
What is the next big milestone in your research field?
This is all about basic science so you never know what will happen. But what the “tool makers” like us would like to identify is the open state structure of a channelrhodopsin. That would help tremendously in designing new variants.
Was it difficult to protect the intellectual property rights of the new technique?
The situation was clear and transparent in 2002. The patent that Georg Nagel and myself wrote with a patent attorney who I knew from the Max-Planck-Institute was relatively clear. But the two universities that I was affiliated with were not interested in this technology as it seemed too risky for them. But luckily the Max-Planck-Institute took over the primary patent and is still promoting it.
What are the biggest challenges for using optogenetics in humans? Optogenetics is primarily an analytic instrument. But applications in the field of retinal prosthesis and deep brain stimulations are on the way and might be realized soon. Our new book Optogenetics provides much more detailed insight into this area.
by Yvonne Kaul