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Studies on CRMP2 SUMOylation-deficient transgenic mice reveal novel insights into the trafficking of NaV1.7 channels

By Kimberly Gomez, Dongzhi Ran, Cynthia L Madura, Aubin Moutal, Rajesh Khanna

Posted 30 Sep 2020
bioRxiv DOI: 10.1101/2020.09.29.318774

Voltage-gated sodium channels are key players in neuronal excitability and pain signaling. Functional expression of the voltage-gated sodium channel NaV1.7 is under the control of SUMOylated collapsin response mediator protein 2 (CRMP2). If not SUMOylated, CRMP2 forms a complex with the endocytic proteins Numb, the epidermal growth factor receptor pathway substrate 15 (Eps15), and the E3 ubiquitin ligase Nedd4-2 to promote clathrin-mediated endocytosis of NaV1.7. We recently reported that CRMP2 SUMO-null knock-in (CRMP2K374A/K374A) female mice have reduced NaV1.7 membrane localization and currents in their sensory neurons. Preventing CRMP2 SUMOylation was sufficient to reverse mechanical allodynia in CRMP2K374A/K374A female mice with neuropathic pain. Here we report that inhibiting clathrin assembly in nerve-injured male and female CRMP2K374A/K374A mice, increased pain sensitivity in allodynia-resistant animals. Furthermore, Numb, Nedd4-2 and Eps15 expression was not modified in basal conditions in the dorsal root ganglia (DRG) of male and female CRMP2K374A/K374A mice. Finally, silencing these proteins in DRG neurons from female CRMP2K374A/K374A mice, restored the loss of sodium currents. Our study shows that the endocytic complex composed of Numb, Nedd4-2 and Eps15, is necessary for non SUMOylated CRMP2-mediated internalization of sodium channels in vivo. ### Competing Interest Statement R. Khanna is the co-founder of Regulonix LLC, a company developing non-opioids drugs for chronic pain. In addition, R. Khanna has patents US10287334 and US10441586 issued to Regulonix LLC. R. The other authors declare no competing financial interest. * Cdk5 : Cyclin-dependent kinase 5 CRMP2 : Collapsin response mediator protein 2 DRG : Dorsal root ganglia Eps15 : Epidermal growth factor receptor pathway substrate 15 k : Slope factor NaV1.7 : voltage-gated sodium channel family 1.7 Nedd4-2 : Neuronal precursor cell expressed developmentally downregulated-4 type 2. SNI : Spinal nerve injury TTX-S : Tetrodotoxin-sensitive V1/2 : Midpoint potentials

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