σ(2)R/TMEM97 in retinal ganglion cell degeneration

The sigma 2 receptor (σ(2)R) was recently identified as an endoplasmic reticulum (ER) membrane protein known as transmembrane protein 97 (TMEM97). Studies have shown that σ(2)R/TMEM97 binding compounds are neuroprotective, suggesting a role of σ(2)R/TMEM97 in neurodegenerative processes. To understand the function of σ(2)R/TMEM97 in neurodegeneration pathways, we characterized ischemia-induced retinal ganglion cell (RGC) degeneration in TMEM97(−/−) mice and found that RGCs in TMEM97(−/−) mice are resistant to degeneration. In addition, intravitreal injection of a selective σ(2)R/TMEM97 ligand DKR-1677 significantly protects RGCs from ischemia-induced degeneration in wildtype mice. Our results provide conclusive evidence that σ(2)R/TMEM97 plays a role to facilitate RGC death following ischemic injury and that inhibiting the function of σ(2)R/TMEM97 is neuroprotective. This work is a breakthrough toward elucidating the biology and function of σ(2)R/TMEM97 in RGCs and likely in other σ(2)R/TMEM97 expressing neurons. Moreover, these findings support future studies to develop new neuroprotective approaches for RGC degenerative diseases by inhibiting σ(2)R/TMEM97.