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

Xie, J. Y., Chew, L. A., Yang, X., Wang, Y., Qu, C., Wang, Y., Federici, L. M., Fitz, S. D., Ripsch, M. S., Due, M. R., Moutal, A., Khanna, M., White, F. A., Vanderah, T. W., Johnson, P. L., Porreca, F., & Khanna, R. (2016). Sustained relief of ongoing experimental neuropathic pain by a CRMP2 peptide aptamer with low abuse potential. PAIN, 157(9), 2124-2140.
Dustrude, E. T., Moutal, A., Yang, X., Wang, Y., Khanna, M., & Khanna, R. (2016). Hierarchical CRMP2 posttranslational modifications control NaV1.7 function. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 113(52), E8443-E8452.
Wang, Y., Brittain, J. M., Wilson, S. M., & Khanna, R. (2010). Emerging roles of collapsin response mediator proteins (CRMPs) as regulators of voltage-gated calcium channels and synaptic transmission. Communicative & integrative biology, 3(2), 172-5.

Presynaptic N-type voltage-gated Ca(2+) channels (Cav2.2) form part of an extensive macromolecular complex in the presynaptic terminal. Regulation of Cav2.2 is achieved via protein-protein interactions within the terminal and can directly impact transmitter release which is dependent on Ca(2+) influx via these Cav2.2. We recently identified a novel Cav2.2 interacting partner-the collapsin response mediator protein (CRMP).1 CRMPs are a family of five proteins implicated in signal transduction of neurite outgrowth and axonal guidance. We showed that CRMP-2, a wellstudied member of this family, interacted with Cav2.2 via direct binding to cytoplasmic loops of Cav2.2. Depolarization enhanced the interaction. Further studies revealed that CRMP-2 facilitated an increase in Cav2.2 current density by inserting more Cav2.2 at the cell surface. As a consequence of CRMP-2-mediated increase in Ca(2+) influx, release of the excitatory neurotransmitter glutamate was also increased. CRMP-2 localized to synapses where, surprisingly, its overexpression increased synapse size. We hypothesize that the CRMP-2-calcium channel interaction represents a novel mechanism for modulation of Ca(2+) influx into nerve terminals and, hence, of synaptic strength. In this addendum, we further discuss the significance of this study and the possible implications to the field.

Khanna, R., Chang, M. C., Joiner, W. J., Kaczmarek, L. K., & Schlichter, L. C. (1999). hSK4/hIK1, a calmodulin-binding KCa channel in human T lymphocytes. Roles in proliferation and volume regulation. The Journal of biological chemistry, 274(21), 14838-49.

Human T lymphocytes express a Ca2+-activated K+ current (IK), whose roles and regulation are poorly understood. We amplified hSK4 cDNA from human T lymphoblasts, and we showed that its biophysical and pharmacological properties when stably expressed in Chinese hamster ovary cells were essentially identical to the native IK current. In activated lymphoblasts, hSK4 mRNA increased 14.6-fold (Kv1.3 mRNA increased 1.3-fold), with functional consequences. Proliferation was inhibited when Kv1.3 and IK were blocked in naive T cells, but IK block alone inhibited re-stimulated lymphoblasts. IK and Kv1.3 were involved in volume regulation, but IK was more important, particularly in lymphoblasts. hSK4 lacks known Ca2+-binding sites; however, we mapped a Ca2+-dependent calmodulin (CaM)-binding site to the proximal C terminus (Ct1) of hSK4. Full-length hSK4 produced a highly negative membrane potential (Vm) in Chinese hamster ovary cells, whereas the channels did not function when either Ct1 or the distal C terminus was deleted (Vm approximately 0 mV). Native IK (but not expressed hSK4) current was inhibited by CaM and CaM kinase antagonists at physiological Vm values, suggesting modulation by an accessory molecule in native cells. Our results provide evidence for increased roles for IK/hSK4 in activated T cell functions; thus hSK4 may be a promising therapeutic target for disorders involving the secondary immune response.

Ripsch, M. S., Ballard, C. J., Khanna, M., Hurley, J. H., White, F. A., & Khanna, R. (2012). A PEPTIDE UNCOUPLING CRMP-2 FROM THE PRESYNAPTIC Ca(2+) CHANNEL COMPLEX DEMONSTRATES EFFICACY IN ANIMAL MODELS OF MIGRAINE AND AIDS THERAPY-INDUCED NEUROPATHY. Translational neuroscience, 3(1), 1-8.

Biological, genetic, and clinical data provide compelling proof for N-type voltage-gated calcium channels (CaV2.2) as therapeutic targets for chronic pain. While decreasing channel function is ultimately anti-nociceptive, directly targeting the channel can lead to multiple adverse effects. Targeting regulators of channel activity may facilitate improved analgesic properties associated with channel block and afford a broader therapeutic window. Towards this end, we recently identified a short peptide, designated CBD3, derived from collapsin response mediator protein 2 (CRMP-2) that suppressed inflammatory and neuropathic hypersensitivity by inhibiting CRMP-2 binding to CaV2.2 [Brittain et al., Nature Medicine 17:822-829 (2011)]. Rodents administered CBD3 intraperitoneally, fused to the HIV TAT protein cell penetrating domain, exhibited antinociception lasting ~4 hours highlighting potential instability, limited oral bioavailability, and/or rapid elimination of peptide. This report focuses on improving upon the parental CBD3 peptide. Using SPOTScan analysis of synthetic versions of the parental CBD3 peptide, we identified peptides harboring single amino acid mutations that bound with greater affinity to CaV2.2. One such peptide, harboring a phenylalanine instead of glycine (G14F), was tested in rodent models of migraine and neuropathic pain. In vivo laser Doppler blood flowmetry measure of capsaicin-induced meningeal vascular responses related to headache pain was almost completely suppressed by dural application of the G14F peptide. The G14F mutant peptide, administered intraperitoneally, also exhibited greater antinociception in Stavudine (2'-3'-didehydro-2'-3'-dideoxythymidine (d4T)/Zerit®) model of AIDS therapy-induced peripheral neuropathy compared to the parent CBD3 peptide. These results demonstrate the patent translational value of small biologic drugs targeting CaV2.2 for management of clinical pain.