Rab7 mutants associated with Charcot-Marie-Tooth disease exhibit enhanced NGF-stimulated signaling

Area of Science:

• Neuroscience
• Cell Biology
• Genetics

Background:

• Missense mutations in the Rab7 GTPase cause Charcot-Marie-Tooth disease type 2B (CMT2B), an autosomal dominant peripheral neuropathy.
• The precise pathological mechanisms linking mutant Rab7 to neuronal dysfunction remain unclear.

Purpose of the Study:

• To investigate the impact of Rab7 CMT2B mutants on nerve growth factor (NGF)-dependent intracellular signaling pathways in PC12 cells.
• To elucidate the molecular mechanisms underlying altered neuronal function in CMT2B.

Main Methods:

• PC12 cells expressing wild-type or CMT2B mutant Rab7 were stimulated with NGF.
• Analyzed TrkA receptor interaction and phosphorylation.
• Assessed downstream signaling pathways, including Erk1/2 and Akt phosphorylation.
• Investigated the nuclear shuttling of phospho-Erk1/2.

Main Results:

• Rab7 CMT2B mutants enhanced TrkA phosphorylation upon NGF stimulation.
• While Akt signaling remained unaffected, Erk1/2 phosphorylation was increased on signaling endosomes.
• Elevated cytoplasmic phospho-Erk1/2 persisted for up to 24 hours.
• Nuclear shuttling of phospho-Erk1/2 was significantly reduced, correlating with inhibited neurite outgrowth.

Conclusions:

• Rab7 CMT2B mutants establish a mechanistic link to altered TrkA and Erk1/2 signaling originating from endosomes.
• The data provide insights into the molecular basis of CMT2B pathogenesis.
• Understanding these signaling disruptions is crucial for developing therapeutic strategies for peripheral neuropathies.