Evidence for a protein tether involved in somatic touch

Area of Science:

• Neuroscience
• Cell Biology
• Biophysics

Background:

• Mechanical force gating of ion channels is fundamental to touch and pain perception.
• The specific gating mechanism of mechanosensitive ion channels in vertebrate touch receptors remains largely unknown.
• Understanding these mechanisms is crucial for deciphering sensory transduction pathways.

Purpose of the Study:

• To investigate the molecular basis of mechanosensitive ion channel gating in vertebrate sensory neurons.
• To identify the structural components responsible for mechanotransduction in low-threshold mechanoreceptors and nociceptors.
• To elucidate the role of protein structures in linking ion channels to the extracellular matrix.

Main Methods:

• Transmission Electron Microscopy (TEM) to visualize protein structures.
• Electrophysiological recordings to measure mechanosensitive currents.
• Treatment with endopeptidases to assess the role of protein tethers.
• In vivo functional assays to evaluate touch-receptor performance.

Main Results:

• A protein filament, approximately 100 nm in length, synthesized by sensory neurons, was identified.
• This protein tether is necessary for mechanosensitive currents in low-threshold mechanoreceptors and some nociceptors of the dorsal root ganglia (DRG).
• Protease treatment destroyed the tethers, abolished mechanosensitive currents, but preserved electrical excitability, indicating a specific role in mechanotransduction.
• Protease-sensitive tethers were confirmed to be essential for in vivo touch-receptor function.

Conclusions:

• A distinct protein tether is required for the mechanical gating of ion channels in cutaneous mechanoreceptors.
• This tether links mechanosensitive ion channels to the extracellular matrix, mediating touch signal transduction.
• Unlike most nociceptors, touch receptors rely on this specific proteinaceous linkage for their function.