CRMP2 protein SUMOylation modulates NaV1.7 channel trafficking

Area of Science:

• Neuroscience
• Molecular Biology
• Ion Channel Physiology

Background:

• Voltage-gated sodium channel (NaV) trafficking is crucial for neuronal function but remains poorly understood.
• Post-translational modifications and protein interactions are proposed mechanisms for NaV trafficking.
• Collapsin response mediator protein 2 (CRMP2) is implicated in NaV function, particularly in modulating slow inactivation by anti-epileptic drugs.

Purpose of the Study:

• To investigate the role of CRMP2 SUMOylation in regulating NaV trafficking, specifically focusing on NaV1.7.
• To determine if CRMP2 SUMOylation affects NaV1.7 surface expression and current density.
• To elucidate a novel regulatory pathway for NaV1.7 channel function.

Main Methods:

• Utilized neuronal model catecholamine A differentiated (CAD) cells and HEK293 cells stably expressing NaV1.7.
• Employed a CRMP2 SUMOylation-incompetent mutant (CRMP2-K374A) to assess the impact of SUMOylation.
• Measured NaV1.7 currents, surface expression via biotinylation, and neurite outgrowth.
• Investigated the role of SUMOylation and deSUMOylation enzymes (SENP1, SENP2) and the E2-conjugating enzyme Ubc9.

Main Results:

• CRMP2 SUMOylation-incompetent mutant (CRMP2-K374A) expression significantly reduced NaV1.7 currents and surface levels in CAD cells.
• Increased deSUMOylation by SENP1/SENP2 decreased NaV1.7 currents in wild-type CRMP2-expressing cells.
• CRMP2-K374A expression reduced NaV1.7 currents in HEK293 cells dependent on Ubc9, but not NaV1.1 or NaV1.3.
• CRMP2 mutation moderately reduced neurite outgrowth but did not affect lacosamide-induced NaV slow inactivation.

Conclusions:

• CRMP2 SUMOylation is a novel regulatory mechanism controlling NaV1.7 trafficking and surface expression.
• This SUMOylation-dependent pathway specifically impacts NaV1.7 channels, influencing their functional contribution.
• The findings provide new insights into the complex regulation of ion channel function in neurons.