Slc66a1, also known as PQLC2, is a lysosomal cationic amino acid transporter. It plays a crucial role in maintaining amino acid homeostasis within cells, transporting lysine, arginine, and histidine across the lysosomal membrane. PQLC2 is involved in the lysosomal sensing of cationic amino acids and recruits a protein complex composed of C9orf72, SMCR8, and WDR41 to the lysosomal surface in response to amino acid scarcity, which is important for regulating multiple aspects of lysosome function [2,3].

Mutations in SLC66A1 have been associated with autosomal recessive retinitis pigmentosa (ARRP), suggesting its significance in retinal function [1]. In four families, SLC66A1 was proposed as a likely novel cause for autosomal recessive rod-cone dystrophy through copy-number analysis of genome sequencing data in rare-disease parent-child trios [4].

In conclusion, Slc66a1, or PQLC2, is essential for lysosomal cationic amino acid transport and sensing, with implications for lysosome function. The identification of its association with autosomal recessive retinal diseases through genetic analyses in human families highlights its importance in understanding the pathogenesis of these disorders.