Structural basis of norepinephrine recognition and transport inhibition in neurotransmitter transporters

Dr. Shabareesh Pidathala’s interview with Bio Patrika hosting “Vigyaan Patrika”, a series of author interviews. Dr. Pidathala received his schooling in a small town called Bellampaly in the present state of Telangana. As a school kid, he had always been interested in chemistry and biology. This interest directed him to do a bachelor’s in botany, chemistry and biotechnology from Sri Venkateshwara University, Tirupati, Andhra Pradesh. He went on to pursue a master’s in biotechnology from Pondicherry central university. He continued his scientific quest as a Ph.D. scholar at the National Institute of Immunology, New Delhi, where he worked at the interface of peptide chemistry and protein biochemistry. He designed, synthesized and carried out structure-activity studies on (glyco)peptides that can inhibit human thrombin, which has the potential to prevent undesirable blood clotting. Post Ph.D., he joined Dr. Aravind Penmatsa’s lab at the Indian Institute of Science to understand the structural basis of proteins involved in neurotransmitter transport. Here, Shabareesh talks about his work on Structural basis of norepinephrine recognition and transport inhibition in neurotransmitter transporters published in Nature Communications.

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How would you explain your paper’s key results to the non-scientific community?

Communication between nerve cells (neurons) happens with the help of chemicals called neurotransmitters. These chemicals are released from one nerve cell and bind to the proteins present on adjacent nerve cells’ surfaces to further relay the information. Excess neurotransmitters released are transported back into the nerve cell. For this uptake of the neurotransmitter, dedicated transporter proteins are present in the cell membranes of nerve cells; they are called neurotransmitter transporters. These transporters play a crucial role in regulating the strength and duration of communication between neurons. Noradrenaline (also known as norepinephrine) is a neurotransmitter that is important in regulating alertness, pain sensation and arousal. Increasing the levels of noradrenaline in the spinal cord was found to relieve chronic pain. One way of doing this is by blocking the neurotransmitter transporter from uptaking the released noradrenaline. Several prescribed medications to treat chronic pain conditions act by blocking the transport of noradrenaline by neurotransmitter transporter. These medications include S-duloxetine, milnacipran and tramadol, which are commercially available as Cymbalta, Savella and Ultracet that are used to treat fibromyalgia, neuropathic pain and post-operative pain, respectively. Our study shows at an atomic level how a neurotransmitter transporter recognizes noradrenaline and how duloxetine, milnacipran, and tramadol block the transporter. Through these structural studies we identified a region in the binding pocket of the transporter crucial for the recognition of noradrenaline and the blockers. These results can help in designing effective pain medications with reduced side effects.

Schematic

Our study provides a detailed structural understanding of noradrenaline recognition by a neurotransmitter transporter.

What are the possible consequences of these findings for your research area?

In the neurotransmitter transporters research field, structures of only three major neurotransmitter transporters are known so far, they include dopamine transporter, serotonin transporter and glycine transporter. Noradrenaline and dopamine are chemically very similar and yet have very different physiological effects. So far, it has not been understood structurally how a neurotransmitter transporter recognizes noradrenaline and how it is different or similar to that of dopamine recognition. Our study provides a detailed structural understanding of noradrenaline recognition by a neurotransmitter transporter. Besides this, it also provides structural insights into recognizing clinically significant blockers of noradrenaline transport used to manage chronic pain conditions. Our structural observations resulted in the identification of a novel region in the transporter, which is crucial for the specific recognition of noradrenaline and the blockers. This information can be essential in designing effective medications to treat chronic pain.

What was the exciting moment (eureka moment) during your research?

Navigating through this project was an exciting journey, and there were several eureka moments for me. We determined six different structures in this project; seeing the electron density map for every structure had been equally exciting. If I have to name one, then it would be observing the clear electron density map for noradrenaline. Working with noradrenaline is tricky as it gets oxidized easily, leading to the formation of undesirable quinones. Hence, crystallization experiments were done with minimal illumination at 4°C along with an anti-oxidant to prevent the oxidation of noradrenaline. Seeing an unambiguous electron density for noradrenaline was very gratifying and gave us the much-needed confidence to execute this project successfully.

What do you hope to do next?

My journey in the field of structural biology continues. Understanding how biomolecules work at an atomic scale always excites me. Electron cryo-microscopy (Cryo-EM) is dominating the field of structural biology and is making it possible to study unimaginably large molecular complexes both in vitro and in situ. I am very keen on pursuing my future research in this field.

Where do you seek scientific inspiration?

My interest in science started during my childhood. My father used to talk to me about Dr. A.P.J. Abdul Kalam’s painstaking journey in his pursuit of scientific knowledge. It was the same time when I used to save my pocket money to purchase a monthly edition of “Science Reporter,” a scientific magazine being published by CSIR. It used to provide a gist of the latest research done in premier research institutes around the globe. These initial seeds of interest directed me to make scientific research my career option. Whenever I hit a roadblock in doing my research, one thing that always motivates me is this quote by Madam Curie “Nothing in life is to be feared, it is only to be understood.” I believe scientific research is the only way to understand this world better and fear less.

How do you intend to help Indian science improve?

I believe the Indian scientific diaspora is very diverse and robust. Given a conducive environment to foster rich collaborations, we can easily be the global leaders in scientific research. My contribution to Indian science will continue; hopefully as an academician, and I will strive to initiate and be part of any appropriate collaborative research. Moreover, it’s our collective responsibility to communicate science better and cultivate the habit of scientific inquiry among people.

Reference

Pidathala, S., Mallela, A.K., Joseph, D. et al. Structural basis of norepinephrine recognition and transport inhibition in neurotransmitter transporters. Nat Commun 12, 2199 (2021). https://doi.org/10.1038/s41467-021-22385-9https://www.iisc.ac.in/how-does-chronic-pain-medication-block-noradrenaline-transport/

Highlight: https://www.iisc.ac.in/how-does-chronic-pain-medication-block-noradrenaline-transport/

Penmatsa lab: https://aplabmbu.weebly.com/

Edited by: Vikramsingh Gujar

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