# TMEM251 loss-induced autophagy dysfunction in the anterior cingulate cortex contributes to chronic postoperative pain

## TL;DR

This study shows that loss of TMEM251 in the brain's ACC leads to autophagy dysfunction, which contributes to chronic postoperative pain.

## Contribution

The novel finding is that TMEM251 deficiency impairs autophagy and causes chronic pain through synaptic protein accumulation in ACC neurons.

## Key findings

- TMEM251 deficiency reduces lysosomal hydrolase levels and autophagic flux in the ACC.
- TMEM251 overexpression rescues autophagy and reduces chronic postoperative pain in mice.
- CaMKIIα-positive neurons in the ACC are particularly affected by autophagy dysfunction.

## Abstract

Macroautophagy/autophagy plays a crucial role in maintaining nervous system homeostasis but its role in chronic postoperative pain (CPOP) remains poorly understood. Here, we identify impaired autophagy and the accumulation of synaptic proteins in the anterior cingulate cortex (ACC) during the maintenance of CPOP after skin/muscle incision and retraction (SMIR). Lysosomal hydrolase levels are reduced upon SMIR, accompanied by a deficiency of the lysosomal trafficking protein transmembrane protein 251 (TMEM251, also named LYSET). TMEM251 overexpression alleviates impaired autophagy, accumulation of synaptic proteins within autophagy substrates, and maintenance of CPOP in SMIR mice. Conversely, TMEM251 knockdown induces autophagy impairment, accumulation of synaptic proteins, and chronic pain phenotypes in naive mice. Autophagy dysfunction is most pronounced in CaMKIIα-positive neurons in the ACC post-surgery, resulting in their activation, which is mitigated by TMEM251 overexpression. Chemogenetic activation of CaMKIIα neurons exacerbates autophagy impairment and CPOP, while their inhibition rescues SMIR-induced autophagy and pain phenotypes. Taken together, our study highlights the close relationship between impaired autophagy and neuronal activation in the promotion of chronic postoperative pain.

In the absence of TMEM251 the decreased lysosomal localization of cathepsin B impairs autophagic flux. The resultant accumulation of PSD95 and activation of pyramidal neurons contributes to the maintenance of postoperative pain.

Impaired neuronal autophagy sensitizes neurons by promoting synaptic protein accumulation in the ACC, which contributes to the maintenance of chronic postoperative pain (CPOP).The sustained activation of CaMKIIα-positive neurons in the ACC further impairs defective autophagy.TMEM251 deficiency results in decreased lysosomal localization of hydrolases, which is involved in the reduction of autophagic flux observed in the ACC of mice experiencing CPOP.

Impaired neuronal autophagy sensitizes neurons by promoting synaptic protein accumulation in the ACC, which contributes to the maintenance of chronic postoperative pain (CPOP).

The sustained activation of CaMKIIα-positive neurons in the ACC further impairs defective autophagy.

TMEM251 deficiency results in decreased lysosomal localization of hydrolases, which is involved in the reduction of autophagic flux observed in the ACC of mice experiencing CPOP.

In the absence of TMEM251 the decreased lysosomal localization of cathepsin B impairs autophagic flux. The resultant accumulation of PSD95 and activation of pyramidal neurons contributes to the maintenance of postoperative pain.