From Berlin to Hyderabad: How a Nobel Prize for Light-Switched Proteins Reached Parasite Research

The 2026 Nobel Prize in Physiology or Medicine has been awarded to Karl Deisseroth, Peter Hegemann and Georg Nagel "for their discoveries concerning light-gated ion channels and optogenetics". The award has renewed attention on a technique that allows scientists to use light to study fundamental biological processes — among them memory formation, emotion and behaviour linked to neurological and psychiatric disorders, as well as the workings of infectious disease.

Optogenetics enables researchers to control selected cells or biological processes using light-sensitive proteins. The Nobel Committee for Physiology or Medicine explained how the field began: "It all began with Peter Hegemann's curiosity. He wondered how Chlamydomonas, a single-celled alga, is able to swim towards a light source." In the early 2000s, Hegemann and Nagel discovered channelrhodopsin, an algal protein found on the surface of the cell. When blue light falls on it, a channel opens through the protein, charged ions flow into the cell, and an electrical impulse is created. The committee noted that whichever cell they placed the protein in, that cell became light-sensitive.

In 2005, Deisseroth showed that introducing channelrhodopsin into rat neurons allowed blue light to trigger nerve signals. By 2007, he had demonstrated light-based control in mice.

For Nishith Gupta, professor of biological sciences at BITS Pilani, Hyderabad, and founder of the Intracellular Parasite Education and Research Labs (iPEARL), the recognition carries personal significance in his own scientific journey.

Mr. Gupta's decades-long collaboration with Mr. Hegemann at Humboldt University of Berlin — where Mr. Hegemann is the Hertie Senior Professor of Neuroscience — helped extend optogenetic approaches beyond neuroscience into the study of Toxoplasma gondii, an intracellular parasite that infects humans, mammals and birds.

The parasite is widespread. Estimates suggest a large proportion of people worldwide carry it, usually with mild or no symptoms. In people with weakened immunity and in pregnant women, however, the infection can cause serious illness, which is why understanding how the parasite enters, moves within and exits cells matters for treatment.

Instead of channelrhodopsin, Mr. Gupta, Mr. Hegemann and their colleagues used a light-regulated enzyme, adenylate cyclase, which converts adenosine triphosphate (ATP) — the primary energy currency of a living cell — into cyclic Adenosine Monophosphate (cAMP). This molecule acts as a messenger, helping transmit signals within cells.

Put simply, the researchers showed that light controls the enzyme, the enzyme produces cAMP, and cAMP helps regulate what happens inside Toxoplasma gondii: how it enters cells, how it moves and how it exits. The landmark study was published in the Journal of Biological Chemistry in 2013.

Where the laureates' work addresses "one of humanity's great mysteries, how our incredible brain works", Mr. Gupta and his collaborators used light-regulated signalling to investigate the parasite's lifestyle and the course of infection.

Mr. Gupta says that working alongside Mr. Hegemann in Berlin, with their laboratories in neighbouring departments, was an important part of his scientific journey. Joint funding from the German Research Foundation (DFG) supported their collaboration. After Mr. Gupta relocated to India, Mr. Hegemann continued to support his research through Mr. Gupta's Wellcome Trust–DBT Senior Fellowship project at BITS Pilani, and researchers from his team continued to visit Mr. Hegemann's group in Berlin.

For Mr. Gupta, the Nobel Prize awarded to Mr. Hegemann and his fellow laureates underscores the far-reaching consequences of fundamental research. A protein that evolved to help an alga sense light has become a tool for probing the brain, investigating infection and understanding how cells function. The broader lesson, he says, is that technologies developed to answer one biological question can open entirely new avenues of research.

"Light has become more than a means of observation; it is a way to intervene, test, and uncover cause-and-effect relationships," Mr. Gupta says.