Glycine is the smallest amino acid \u2013 one of the building blocks of proteins. It acts also as a neurotransmitter in the brain, enabling neurons to communicate with each other and modulating neuronal activity. Many researchers have focused on increasing glycine levels in synapses to find an effective treatment for schizophrenia. This could be done using inhibitors targeting Glycine Transporter 1 (GlyT1), a protein that sits in neuronal cell membranes and is responsible for the uptake of glycine into neurons. However, the development of such drugs has been hampered because the 3D structure of GlyT1 was not known.<\/p>\n\n\n\n
To determine the structure of GlyT1, researchers at the Danish Research Institute of Translational Neuroscience (DANDRITE)<\/a>, which is part of the Nordic EMBL Partnership for Molecular Medicine<\/a>, F. Hoffmann-La Roche, EMBL Hamburg, the University of Zurich, Aarhus University, and Linkster Therapeutics joined forces. \u201cThis project required multidisciplinary collaboration and unique expertise from different labs over several years,\u201d says Azadeh Shahsavar, first author of the study and now an assistant professor at DANDRITE. She performed the measurements for the study during her time as a postdoc in the EMBL Interdisciplinary Postdocs (EIPOD) programme<\/a>, during which she worked at EMBL Hamburg, DANDRITE and Roche.<\/p>\n\n\n\n Poul Nissen, Director of DANDRITE and a senior researcher in the study, comments: \u201cWe are immensely grateful for the EMBL\u2019s EIPOD scheme and the Nordic EMBL Partnership to keep us on track for so long and allow us to explore very difficult approaches. We would not have succeeded without it, and without Azadeh\u2019s persistence of course!\u201d<\/p>\n\n\n\n GlyT1 turned out to be particularly challenging to study, because it is unstable when extracted from the cell membrane. To stabilise it, scientists combined several approaches, such as creating more stable variants of the protein. To catch the transporter in a clinically relevant state, the team used a chemical created by Roche that binds and stabilises GlyT1 from the inside, and designed a synthetic mini-antibody (sybody) that binds it from the outside. <\/p>\n\n\n\n The scientists tested 960 different conditions and managed to obtain GlyT1 crystals in one of them. \u201cThe crystals were very small and difficult to image. We chose to measure them at EMBL Hamburg’s beamline P14, which is well suited for challenging experiments like this one,\u201d says Azadeh. The X-ray beam at P14 is particularly strong and focused, and its equipment has features tailored for work with even micrometre-sized crystals. Yet the quality of the crystals was variable, which made data collection challenging. Eventually, Azadeh\u2019s perseverance paid off. \u201cI remember when I saw electron density of the inhibitor for the first time. I was so excited, I couldn\u2019t sleep for two nights,\u201d she says. \u201cYou live for those rewarding moments.\u201d<\/p>\n\n\n\nOvercoming challenges in studying Glycine Transporter 1<\/h2>\n\n\n\n