MIcroscope manufacturer FEI Corp. has reported that researchers at the NIH-FEI Living Lab for Structural Biology have achieved breakthrough biological results, using FEI’s Titan Krios transmission electron microscope (TEM), to elucidate the structural mechanism by which glutamate receptors participate in the transmission of signals between neurons in the brain. Their work is described in Nature, “Structural Mechanism of Glutamate Receptor Activation and Desensitization.”

“The Living Lab for Structural Biology was designed two years ago as an open innovation framework to bring together cryo-EM, nuclear magnetic resonance (NMR), x-ray diffraction (XRD), and biochemistry experts in one place to develop integrated workflows for enabling solutions to  important structural biology questions,” said Paul Scagnetti, vice president and general manager of FEI’s Sciences Group. “This important biological research result demonstrates the success of the collaboration between FEI and the leading researchers at NIH, such as Dr. Sriram Subramaniam.”

According to Sriram Subramaniam, Ph.D., senior investigator in the National Cancer Institute's Laboratory of Cell Biology and the director of the Living Lab, the prospect that the determination of structures of membrane proteins and related complexes may no longer be limited by size or by the need for crystallization suggests a critical shift in the landscape of structural biology and an exciting new horizon.

According to Mark Mayer, Ph.D., of the Laboratory of Cellular and Molecular Neurophysiology, National Institute of Child Health and Human Development (NICHD), an NIH researcher who has traditionally relied on X-ray crystallograpy to study important membrane proteins and an author on the Nature paper, iGluRs are major mediators of excitatory synaptic transmission in the brain and also play key roles in nearly all aspects of nervous system development, learning and memory. Their dysfunction is associated with major neurodegenerative and psychiatric disorders, including Alzheimer's and Parkinson's diseases, stroke, epilepsy, schizophrenia and depression. Understanding the molecular function of glutamate receptors will allow greater insight into their gating mechanisms, and allow development of therapies targeting these diseases.

A major challenge in membrane protein structural biology is the crystallization of ion channels and receptors in different functional states; with crystals in hand the most widely used approach to solve structures at atomic resolution is the collection of x-ray diffraction data. However, many membrane proteins are resistant to crystallization, and trapping them in different functional states is even more of a challenge, since the crystal lattice often selects for just one of multiple conformational states. This is especially true for glutamate receptor ion channels, which have three major conformations, a resting state, an active state, and a desensitized state, in which the receptor has bound glutamate, but no longer transmits ion channel activity. Even more challenging, glutamate receptors activate and desensitize on the millisecond time scale.

The multiple conformations of the proteins in the glutamate receptor family were solved utilizing FEI's Titan Krios TEM equipped with an XFEG and spherical aberration image corrector, Falcon generation II direct electron detector, and FEI EPU software, which enables 24/7 uninterrupted automated cryo-EM image collection.

Scagnetti adds, “The research relied on the automated and robust workflows for protein structure determination that were developed in the NIH-FEI Living Lab—and this was a major goal of the collaboration.”

FEI announced the Living Lab Structural Biology Center at NIH in 2012 as part of a cooperative research and development agreement. Located on the NIH campus, the facility houses many FEI instruments used for biological structural determination including a Titan Krios TEM, the world’s most powerful commercially-available electron microscope for structural biology. Experts from the National Cancer Institute (NCI), the Institute of Diabetes and Digestive and Kidney Diseases, (NIDDK) , and other Institutes of the NIH, such as the  NICHD, and FEI, work together at the at the Living Lab to develop new methods and workflows, from sample preparation through data analysis, for cryo-electron microscopy.

Study: Structural mechanism of glutamate receptor activation and desensitization

NIH-FEI Living Lab for Structural Biology

Source: FEI Corp.