2023 MSC Poster Contest Presentation: Multiple Rab GTPase subtypes are involved in Nav1.7 anterograde transport in sensory axons

The 2023 MSC Emerging Science Contest for Early-Career Investigators took place on December 13, 2023. Below is a written summary of one of the presentations from the contest. Read about other presentations from the event in our Early-Career Science Library.

Category: Pain

Runner up: Nivedita Sarveswaran, postdoctoral researcher, Yale University School of Medicine & VA-CT, US

Title: Multiple Rab GTPase subtypes are involved in Nav1.7 anterograde transport in sensory axons.

Hypothesis, methodology, findings and conclusions

Voltage-gated sodium channel Nav1.7 is an attractive target for analgesic drug development given its key role as a threshold channel for action potential generation in nociceptors. Past attempts to block these sodium currents via extracellular compounds have had limited success in clinical trials; therefore we have begun to investigate protein partners involved in intracellular trafficking as an alternative approach to reducing Nav1.7 surface expression.

The recent evolution of fluorescent probes, compartmentalized culture systems that isolate neuronal cell bodies from axons, and advancements in live microscopy techniques led to the advent of Optical Pulse-chase Axonal Long-distance (OPAL) imaging. This assay facilitates the real-time tracking of tagged proteins during axonal transport, while additional protocols can generate sensitive measurements of cell surface expression.

We studied a selection of Rab GTPase proteins known to regulate cargo sorting into membrane-bound vesicles at various subcellular locations, expanding on our previous work that highlighted Rab6A as a Nav1.7 trafficking partner. We showed that Rab6A inactivation reduces its ability to co-traffic with Nav1.7, however, it did not have a significant effect on Nav1.7 surface expression levels. We later found additional Rab proteins, Rab11A and Rab15, were also co-transported in Nav1.7-positive vesicles and were frequently found together with Rab6A – likely offering a layer of redundancy to maintain physiological regulation of Nav1.7 transport.

Further work is needed to investigate the possibility of more specific protein partners involved in Nav1.7 trafficking, and whether interfering with these functional interactions may fully abrogate nociceptor excitability, thus providing substantial pain relief.

Implications for understanding migraine disease and/or its comorbidities, or how the research holds promise as a new avenue of future migraine study.

The tools we have developed to prepare neuronal cultures from dorsal root ganglia could easily be applied to visualize the axonal trafficking of proteins of interest in trigeminal sensory neurons. For example, one could investigate the subcellular trafficking of ion channels associated with trigeminal nociceptor excitability (e.g., TRESK potassium channels) as an avenue for dampening migraine-associated activity.