TMEM 55B contributes to lysosomal homeostasis and amino acid–induced mTORC 1 activation

TMEM55B modulates lysosome function.

“TMEM55B is localized to the late endosome and lysosome7, and has been shown to impact lysosome function23, 28.”

TMEM55B impacts lysosome function.

“TMEM55B is localized to the late endosome and lysosome7, and has been shown to impact lysosome function23, 28.”

Depletion of TMEM55B in mice is embryonic lethal.

“Since depletion of TMEM55B in mice was shown to be embryonic lethal34, we decided to use zebrafish as model system.”

TMEM55B regulates autophagosome-lysosome fusion, lysosomal repair, and TFE3 nuclear translocation under stress, interacts with amino-acid sensing complexes, and modulates cholesterol metabolism via PI(4,5)P2 phosphatase activity.

“TMEM55B also regulates autophagosome-lysosome fusion, lysosomal repair, and TFE3 nuclear translocation under stress (Jeong et al. 2024), interacts with amino-acid sensing complexes (Hashimoto et al. 2018), and modulates cholesterol metabolism via PI(4,5)P2 phosphatase activity (Qin et al. 2020).”

TMEM55B associates with V-ATPase/Ragulator to regulate mTORC1 and controls PI(4,5)P2-dependent LDLR and cholesterol metabolism.

“TMEM55B associates with V-ATPase/Ragulator to regulate mTORC1 (Hashimoto et al. 2018) and controls PI(4,5)P2-dependent LDLR and cholesterol metabolism (Qin et al. 2020).”

Knockout of TMEM55B leads to lysosomal stress and loss of vATPase function related to lysosomal acidification.

“Knockout of TMEM55B leads to lysosomal stress and loss of vATPase function which is related to the acidification of lysosomes (Hashimoto et al., 2018).”

TMEM55B can inhibit TFEB nuclear translocation, thus suppressing expression of lysosomal genes.

“Interestingly, while TMEM55B expression is dependent on TFEB (Willett et al., 2017), TMEM55B can actually inhibit TFEB nuclear translocation (Hashimoto et al., 2018) thus suppressing expression of lysosomal genes.”

TMEM55B is implicated in direct regulation of endo-lysosomal acidification, potentially independently of its trafficking functions.

“TMEM55B is also implicated in direct regulation of endo-lysosomal acidification, potentially independently of its trafficking functions (Hashimoto et al., 2018;Takemasu et al., 2019).”