Mutant TRPV4-mediated toxicity is linked to increased constitutive function in axonal neuropathies

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Mutations in the Transient Receptor Potential Vanilloid 4 (TRPV4) gene are associated with three distinct axonal neuropathies.
• The precise pathogenic mechanism of these TRPV4-linked disorders remains elusive, with both gain-of-function and loss-of-function hypotheses proposed.

Purpose of the Study:

• To investigate the functional consequences of previously reported TRPV4 mutations.
• To elucidate the molecular mechanism underlying TRPV4-associated axonal neuropathies.

Main Methods:

• Patch clamp electrophysiology (whole-cell and single-channel recordings) was used to assess calcium channel activity.
• Cellular localization and cytotoxicity assays were performed on cells expressing wild-type and mutant TRPV4 channels.

Main Results:

• The three studied TRPV4 mutant channels exhibited physiological localization and significantly increased calcium channel activity compared to wild-type.
• Patch clamp data revealed larger whole-cell currents and higher open probability in mutant TRPV4 channels, indicating a gain-of-function mechanism.
• Increased intracellular calcium influx through mutant TRPV4 channels led to enhanced cytotoxicity in multiple cell types.

Conclusions:

• The findings strongly support a gain-of-function mechanism for TRPV4-linked axonal neuropathies, driven by enhanced calcium influx.
• Understanding this mechanism provides a basis for developing targeted therapies for these debilitating neurological disorders.