# Immunohistochemical Detection of Tentonin-3/TMEM150C in Human Dorsal Root Ganglion, Cutaneous End-Organ Complexes, and Muscle Spindles

## TL;DR

This study identifies the presence of a specific protein in human sensory neurons and structures, suggesting its role in mechanical sensation.

## Contribution

First report on the distribution of tentonin-3/TMEM150C in the human peripheral somatosensory system.

## Key findings

- Tentonin-3/TMEM150C is present in 41% of human dorsal root ganglion neurons.
- The protein is found in sensory corpuscles and muscle spindles but not in free nerve endings.
- This study opens new perspectives for understanding mechano-gated ion channels in humans.

## Abstract

Background/Objectives: Tentonin-3/TMEM150C is a pore-forming protein of a mechanically activated channel recently identified that typically displays rapid activation followed by slow inactivation. It has been detected in murine dorsal root ganglia, nodose ganglion baroreceptors, and muscle spindles. Nevertheless, primary sensory neurons expressing tentonin-3/TMEM150C fall into the categories of nociceptors, mechanoreceptors, and proprioceptors. Methods: We used immunohistochemistry and image analysis (examining the size of the neuronal bodies in the dorsal root ganglia) to investigate the distribution of tentonin-3/TMEM150C in human cervical dorsal root ganglia, sensory nerve formations in the glabrous skin, especially cutaneous end-organ complexes or sensory corpuscles, and muscle spindles. Results: In dorsal root ganglia, 41% of neurons were tentonin-3/TMEM150C-positive, with a distribution of small (12.0%), intermediate (18.1%), and large (10.9%). In the glabrous skin, tentonin-3/TMEM150C was observed in the axon of Meissner, Pacinian, and Ruffini corpuscles as well as in the axon of the Merkel cell–axon complexes. Furthermore, tentonin-3/TMEM150C-positive axons were observed in muscle spindles. No free nerve endings displaying immunoreactivity were found. Conclusions: This is the first report on the distribution of tentonin-3/TMEM150C immunoreactivity in the human peripheral somatosensory system, and although it is a brief preliminary study, it opens new perspectives for the study of this new mechano-gated ion channel.