Rajesh Khanna
Professor, Anesthesiology
Professor, BIO5 Institute
Professor, Neuroscience - GIDP
Professor, Pharmacology
Primary Department
Department Affiliations
(520) 626-4281
Work Summary
The focus of my laboratory’s’ research is to understand how ion channels, specifically, voltage-gated calcium and sodium channels, are regulated by novel protein interactions. Recent studies in my laboratory have focused on targeting protein-protein interactions with biologics (peptide aptamers) and small molecules; testing the activity of these novel chemical entities in biochemical and immunofluorescent-based assays of trafficking; examining their protein interaction signatures; testing them with whole cell voltage-clamp electrophysiology and voltage- and calcium sensitive fluorescence-based imaging. Regulating these protein networks to modulate the activity of ion channels in neurodegenerative diseases (Chronic Pain, Migraine, and Neurofibromatosis) is a key focus of the laboratory.
Research Interest
Regulation of Trafficking and Functions of Voltage-Gated Sodium and Calcium Channels; Identification of Novel Protein Regulators of Ion channels; Approaches to Targeting the Ion Channel Complexes in Neuropathic Pain and Neurodegenerative Diseases; Discovery of Novel Biologics and Small Molecules Targeting Pain and Neurodegenerative Diseases

Publications

Quach, T. T., Wang, Y., Khanna, R., Chounlamountri, N., Auvergnon, N., Honnorat, J., & Duchemin, A. (2011). Effect of CRMP3 expression on dystrophic dendrites of hippocampal neurons. Molecular psychiatry, 16(7), 689-91.
Khanna, R., Li, Q., & Stanley, E. F. (2006). 'Fractional recovery' analysis of a presynaptic synaptotagmin 1-anchored endocytic protein complex. PloS one, 1, e67.

The integral synaptic vesicle protein and putative calcium sensor, synaptotagmin 1 (STG), has also been implicated in synaptic vesicle (SV) recovery. However, proteins with which STG interacts during SV endocytosis remain poorly understood. We have isolated an STG-associated endocytic complex (SAE) from presynaptic nerve terminals and have used a novel fractional recovery (FR) assay based on electrostatic dissociation to identify SAE components and map the complex structure. The location of SAE in the presynaptic terminal was determined by high-resolution quantitative immunocytochemistry at the chick ciliary ganglion giant calyx-type synapse.

Khanna, R., Zougman, A., & Stanley, E. F. (2007). A proteomic screen for presynaptic terminal N-type calcium channel (CaV2.2) binding partners. Journal of biochemistry and molecular biology, 40(3), 302-14.

N type calcium channels (CaV2.2) play a key role in the gating of transmitter release at presynaptic nerve terminals. These channels are generally regarded as parts of a multimolecular complex that can modulate their open probability and ensure their location near the vesicle docking and fusion sites. However, the proteins that comprise this component remain poorly characterized. We have carried out the first open screen of presynaptic CaV2.2 complex members by an antibody-mediated capture of the channel from purified rat brain synaptosome lysate followed by mass spectroscopy. 589 unique peptides resulted in a high confidence match of 104 total proteins and 40 synaptosome proteome proteins. This screen identified several known CaV2.2 interacting proteins including syntaxin 1, VAMP, protein phosphatase 2A, G(O alpha), G beta and spectrin and also a number of novel proteins, including clathrin, adaptin, dynamin, dynein, NSF and actin. The unexpected proteins were classified within a number of functional classes that include exocytosis, endocytosis, cytoplasmic matrix, modulators, chaperones, and cell-signaling molecules and this list was contrasted to previous reports that catalogue the synaptosome proteome. The failure to detect any postsynaptic density proteins suggests that the channel itself does not exhibit stable trans-synaptic attachments. Our results suggest that the channel is anchored to a cytoplasmic matrix related to the previously described particle web.

Moutal, A., François-Moutal, L., Perez-Miller, S., Cottier, K., Chew, L. A., Yeon, S. K., Dai, J., Park, K. D., Khanna, M., & Khanna, R. (2016). (S)-Lacosamide Binding to Collapsin Response Mediator Protein 2 (CRMP2) Regulates CaV2.2 Activity by Subverting Its Phosphorylation by Cdk5. Molecular neurobiology, 53(3), 1959-1976.

The neuronal circuit remodels during development as well as in human neuropathologies such as epilepsy. Neurite outgrowth is an obligatory step in these events. We recently reported that alterations in the phosphorylation state of an axon specification/guidance protein, the collapsin response mediator protein 2 (CRMP2), play a major role in the activity-dependent regulation of neurite outgrowth. We also identified (S)-LCM, an inactive stereoisomer of the clinically used antiepileptic drug (R)-LCM (Vimpat®), as a novel tool for preferentially targeting CRMP2-mediated neurite outgrowth. Here, we investigated the mechanism by which (S)-LCM affects CRMP2 phosphorylation by two key kinases, cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3β (GSK-3β). (S)-LCM application to embryonic cortical neurons resulted in reduced levels of Cdk5- and GSK-3β-phosphorylated CRMP2. Mechanistically, (S)-LCM increased CRMP2 binding to both Cdk5- and GSK-3β without affecting binding of CRMP2 to its canonical partner tubulin. Saturation transfer difference nuclear magnetic resonance (STD NMR) and differential scanning fluorimetry (DSF) experiments demonstrated direct binding of (S)-LCM to CRMP2. Using an in vitro luminescent kinase assay, we observed that (S)-LCM specifically inhibited Cdk5-mediated phosphorylation of CRMP2. Cross-linking experiments and analytical ultracentrifugation showed no effect of (S)-LCM on the oligomerization state of CRMP2. The increased association between Cdk5-phosphorylated CRMP2 and CaV2.2 was reduced by (S)-LCM in vitro and in vivo. This reduction translated into a decrease of calcium influx via CaV2.2 in (S)-LCM-treated neurons compared to controls. (S)-LCM, to our knowledge, is the first molecule described to directly inhibit CRMP2 phosphorylation and may be useful for delineating CRMP2-facilitated functions.

Wilson, S. M., Moutal, A., Melemedjian, O. K., Wang, Y., Ju, W., Francois-Moutal, L., Khanna, M., & Khanna, R. (2014). The functionalized amino acid (S)-Lacosannide subverts CRMP2-mediated tubulin polymerization to prevent constitutive and activity-dependent increase in neurite outgrowth. FRONTIERS IN CELLULAR NEUROSCIENCE, 8.