TMEM33 of 247 aas and 4 TMSs.  Acts as a regulator of the tubular endoplasmic reticulum (ER) network. Suppresses the RTN3/4-induced formation of the ER tubules (Urade et al. 2014). Positively regulates PERK-mediated and IRE1-mediated unfolded protein response signaling (Sakabe et al. 2015).TMEM33 in mice regulates Ca2+ fluxes by interacting with the ion channel polycystin-2 (PC2) at the ER membrane, enhancing its opening over the whole physiological calcium range (Urade et al. 2014). Positively regulates PERK-mediated and IRE1-mediated unfolded protein response signaling (Sakabe et al. 2015).TMEM33 in mice regulates Ca2+ fluxes by interacting with the ion channel polycystin-2 (PC2) at the ER membrane, enhancing its opening over the whole physiological calcium range (Sakabe et al. 2015).TMEM33 in mice regulates Ca2+ fluxes by interacting with the ion channel polycystin-2 (PC2) at the ER membrane, enhancing its opening over the whole physiological calcium range (Arhatte et al. 2019).