Neurospecific transmembrane protein 240 colocalizes with peroxisomes and activates Rho GDP dissociation inhibitor β

HU Qiongqiong; LI Wenpei; XU Lixia; GUAN Ruilei; ZHANG Dongya; JIANG Jiaojiao; WANG Ning; YANG Gaiqing

doi:10.12122/j.issn.1673-4254.2025.06.15

Abstract：Objective To investigate the subcellular localization and biological functions of transmembrane protein 240(TMEM240).Methods NCBI BLAST and TMHMM bioinformatics software were used for protein sequence analysis and prediction of transmembrane domain of TMEM240.Brain tissues from male C57BL/6 mice(18-20 days old)were examined for distribution of TMEM240 using in situ hybridization,and qPCR and Western blotting were used to detect TMEM240 expression in different mouse tissues and in cortical neurons at different time points(n=3).In the in vitro experiment,HepG2 and Neuro-2a cells were transfected with plasmids for overexpression of TMEM240,and subcellular localization of TMEM240 was analyzed using cell imaging.In primary cultures of cortical neurons isolated from C57BL/6 mice,TMEM240 expression and its biological functions were investigated using qPCR,Western blotting,and immunofluorescence staining.Results Human and mouse TMEM240 proteins share a 97.69%similarity in the protein sequences,and both are transmembrane proteins with two transmembrane domains.TMEM240 mRNA and protein were highly expressed in mouse brain tissues and cortical neurons.In isolated mouse cortical neurons,TMEM240 expression reached the peak level after primary culture for 9 days and distributed in scattered spots within the cells.In HepG2 cells,TMEM240 was characterized as intracellular membrane structures and showed 80%colocalization with peroxisomes.In Neuro-2a cells,TMEM240 overexpression caused significant enhancement of the expressions of Rho GDP dissociation inhibitor β(ARHGDIB)at both the mRNA and protein levels.Conclusion TMEM240 is a novel intracellular subcellular structure specifically expressed in neurons with significant potential for targeted cellular function regulation.