ZMYND19 is a zinc finger MYND-type protein that functions as a negative regulator of mTORC1 signaling at the lysosomal membrane. As a substrate of the CTLH E3 ubiquitin ligase complex, ZMYND19 is degraded via the ubiquitin/proteasome pathway, with its stability conditionally regulated by TNF-α stimulation and mTOR inhibition 1. When accumulated (upon CTLH inhibition), ZMYND19 associates with lysosomes and MKLN1 to inhibit mTORC1 activation by blocking the interaction between mTORC1 and its activator Rheb, as well as mTORC1 substrates S6 and 4E-BP1 23. ZMYND19 is recruited by the GID4 adaptor subunit of the hGID E3 ligase complex, which regulates its ubiquitination 4. Structurally, ZMYND19's MYND zinc-finger domain mediates binding to tubulin 5, and the protein localizes to cytoplasmic, membrane, and synaptosomal compartments, with somatodendritic localization in neurons 6. In hepatocellular carcinoma, ZMYND19 expression is upregulated through a lncRNA FABP5P3/miR-589-5p regulatory axis, promoting cell proliferation, migration, and invasion 7, suggesting pathological roles in cancer development.