Rashna Balsara, PhD

Research Associate Professor of Chemistry and Biochemistry

Rashna - Balsara, PhD

Contact Info

Phone: 574-631-2958
Email: rbalsara@nd.edu

Biography

2014–present Research Associate Professor, University of Notre Dame
2007–2014 Research Assistant Professor, University of Notre Dame
2005–2007 Walther Cancer Research Fellow, University of Notre Dame
2002–2005 Postdoctoral Fellow, University of Notre Dame
2001–2002 NIH Training Fellow, University of Illinois Urbana–Champaign
1998–2000 Postdoctoral Fellow, University of Illinois Urbana–Champaign
1998 Ph.D in Molecular Biology, Bombay University
1991 M.S. in Molecular Biology, Bombay University
1985 B.S. in Microbiology, Bombay University

 Honors & Awards

2005–2007 Walther Cancer Research Fellowship
1994 Young Scientist Fellowship
1991–1996 Council of Scientific and Industrial Research Fellowship, Government of India

Research Interests

Stroke is a major cause of death and disability in the United States. According to the Center for Disease Control, over 800,000 people die in the U.S. each year from stroke. Following stroke, prolonged neuronal death occurs, and, to date, suitable neuroprotective therapeutics are not clinically available due to their averse side effects and short therapeutic window. Therefore, understanding the underlying mechanisms that causes neuronal death can lead to drug development that can minimize stroke damage. Although, damage accompanying stroke is multifactorial, the N-methyl-D-aspartate receptors (NMDAR) excitotoxicity is the dominant cause of neuronal destruction. The NMDAR are ligand- and voltage-gated ion channels co-agonized by glutamate and glycine. The receptors are hetero-oligomeric proteins consisting of the mandatory GluN1 (a-h) subunit and GluN2 (A-D) subunit(s) conferring functional and pharmacological diversity. When activated under physiological conditions the NMDAR plays a central role in synaptic transmission mediating synaptic plasticity, learning, and memory. However, pathological activation of the NMDAR, in particular the GluN2B subunit, contributes to neurotoxicity in different disorders, such as ischemia, trauma, epilepsy, and Alzheimer’s disease. This has prompted several investigators to search for and/or design effective NMDAR-directed therapies. One such set of NMDAR-specific antagonists are the conantokins. These peptides are found in the venoms of marine snails and contain the unusual post-transitionally modified amino acid, γ-carboxyglutamate (Gla) that confers to the peptide its biological activity.

Currently, at the Keck Center we are utilizing conantokins, and other GluN subunit-specific inhibitors as pharmacological tools, in combination with state-of-the-art techniques, such as anatomic labeling strategies and live brain electrophysiology to detect in real-time, changes in ischemia-induced intrinsic electrophysiological properties of neurons. Furthermore, the GluN-specific conantokins are also utilized to understand how NMDAR localization and function are affected during an ischemic stroke and the implications of these changes on neuronal functioning. In this manner, we are able to electrophysiologically isolate and map ischemia-induced NMDAR-driven alterations in neuronal circuitry and intrinsic electrical functions of neurons.

Another aspect of this project was to elucidate structure-function relationship of conantokin interactions with NMDAR. Structural information of conantokins and their variants, in which key residues have been strategically shuffled have been correlated with NMDAR inhibitory potency and GluN subunit specificity using natural and model cell lines that express different combinations of GluN subunits. To further understand the role of glutamate/glycine coagonism on NMDAR channel activation, the ligand binding domains (LBD) of GluN1, GluN2A, and GluN2B were purified and homomeric and heteromeric interactions were elucidated. Sedimentation velocity and equilibrium studies demonstrated that the LBDs of NMDARs hetero-dimerize only when both the coagonists, viz., glycine/D-serine and L-glutamate are bound to their sites on GluN1 and GluN2A subunits, respectively. In the absence of agonists, these subunit regions form homomeric interactions, which are disrupted upon agonist binding. The binding of glycine to the GluN1 LBD results in higher affinity for glutamate at the GluN2A LBD, but not vice versa.

Recent Papers

Yuan Y, Balsara RD, Zajicek J, Kunda S, Castellino FJ. Discerning the Role of the Hydroxyproline Residue in the Structure of Conantokin Rl-B and Its Role in GluN2B Subunit-Selective Antagonistic Activity toward N-Methyl-d-Aspartate Receptors. Biochemistry. 2016 Dec 27;55(51):7112-7122. doi: 10.1021/acs.biochem.6b00962. Epub 2016 Dec 16. PMID: 27981829

Cheriyan J, Balsara RD, Hansen KB, Castellino FJ. Pharmacology of triheteromeric N-Methyl-D-Aspartate Receptors. Neurosci Lett. 2016 Mar 23;617:240-6. doi: 10.1016/j.neulet.2016.02.032. Epub 2016 Feb 23. PMID: 26917100

Kunda S, Yuan Y, Balsara RD, Zajicek J, Castellino FJ. Hydroxyproline-induced Helical Disruption in Conantokin Rl-B Affects Subunit-selective Antagonistic Activities toward Ion Channels of N-Methyl-d-aspartate Receptors. J Biol Chem. 2015 Jul 17;290(29):18156-72. doi: 10.1074/jbc.M115.650341. Epub 2015 Jun 5. PMID: 26048991

Balsara R, Dang A, Donahue DL, Snow T, Castellino FJ. Conantokin-G attenuates detrimental effects of NMDAR hyperactivity in an ischemic rat model of stroke. PLoS One. 2015 Mar 30;10(3):e0122840. doi: 10.1371/journal.pone.0122840. eCollection 2015 Mar 30. PMID: 25822337

Balsara RD, Chapman SE, Sander IM, Donahue DL, Liepert L, Castellino FJ, Leevy WM. Non-invasive imaging and analysis of cerebral ischemia in living rats using positron emission tomography with 18F-FDG. J Vis Exp. 2014 Dec 28;(94). doi: 10.3791/51495. PMID: 25590998

Cheriyan J, Mezes C, Zhou N, Balsara RD, Castellino FJ. Heteromerization of ligand binding domains of N-methyl-D-aspartate receptor requires both coagonists, L-glutamate and glycine. Biochemistry. 2015 Jan 27;54(3):787-94. doi: 10.1021/bi501437s. Epub 2015 Jan 8. PMID: 25544544

Huang L, Balsara RD, Castellino FJ. Synthetic conantokin peptides potently inhibit N-methyl-D-aspartate receptor-mediated currents of retinal ganglion cells. J Neurosci Res. 2014 Jul 10. doi: 10.1002/jnr.23447. [Epub ahead of print]. PMID:25043917

Balsara RD, Ferreira AN, Donahue DL, Castellino FJ, Sheets PL. Probing NMDA receptor GluN2A and GluN2B subunit expression and distribution in cortical neurons. Neuropharmacology. 2014 Apr;79:542-9. doi: 10.1016/j.neuropharm.2014.01.005. Epub 2014 Jan 15. PMID:24440368

Kunda S, Cheriyan J, Hur M, Balsara RD, Castellino FJ (2013). Antagonist properties of Conus pariuspeptides on N-methyl-D-aspartate receptors and their effects on CREB signaling. PLoS One. Nov 18;8(11):e81405. doi: 10.1371/journal.pone.0081405. eCollection 2013. PMID:24260577

Balsara RD, Li N, Weber-Adrian D, Huang L, Castellino FJ. (2012). Opposing action of conantokin-G on synaptically and extrasynaptically-activated NMDA receptors. Neuropharmacology. 62(7): 2226-2237. Jun;62(7):2227-38. doi: 10.1016/j.neuropharm.2012.01.018. Epub 2012 Jan 27. PMID:22306487

Huang L, Balsara RD, Sheng Z, Castellino FJ. (2010). Conantokins inhibit NMDAR-dependent calcium influx in developing rat hippocampal neurons in primary culture with resulting effects on CREB phosphorylation. Mol Cell Neurosci. 45(2):163-172. doi: 10.1016/j.mcn.2010.06.007. Epub 2010 Jun 21. PMID:21535874

Agrahari G, Liang Z, Mayfield JA, Balsara RD, Ploplis VA, Castellino FJ. (2013). Complement-mediated opsonization of invasive group A Streptococcus pyogenes strain AP53 is regulated by the bacterial two-component cluster of virulence responder/sensor (CovRS) system. J Biol Chem 288(38):27494-27504. doi: 10.1074/jbc.M113.494864. Epub 2013 Aug 8. PMID:23928307

Liang Z, Zhang Y, Agrahari G, Chandrahas V, Glinton K, Donahue DL, Balsara RD, Ploplis VA, Castellino FJ. (2013). A natural inactivating mutation in the CovS component of the CovRS regulatory operon in a pattern D Streptococcal pyogenes strain influences virulence-associated genes. J Biol Chem. 288(9):6561-6573. doi: 10.1074/jbc.M112.442657. Epub 2013 Jan 13. PMID:23316057