Endoplasmic reticulum membrane protein that promotes endoplasmic reticulum-associated endosome fission. Localizes to contact sites between the endoplasmic reticulum and endosomes and acts by promoting recruitment of the endoplasmic reticulum to endosome tubules for fission. Endosome membrane fission of early and late endosomes is essential to separate regions destined for lysosomal degradation from carriers to be recycled to the plasma membrane. May form homodimers and heterodimers with TMCC2 or TMCC3 via the coiled-coil domains. Interacts with ribosomal proteins RPL4 and RPS6. Specifically localizes to contact sites between the endoplasmic reticulum and endosomes that are spatially and temporally linked to endosome fission. Belongs to the TEX28 family.