MTMR3 is a lipid phosphatase that dephosphorylates phosphatidylinositol 3-phosphate (PtdIns3P) and phosphatidylinositol 3,5-bisphosphate, regulating both membrane trafficking and cell signaling 1234. Beyond its catalytic function, MTMR3 possesses molecular adaptor activity and regulates midbody abscission during cytokinesis 5. MTMR3 interacts with mTORC1 and suppresses its activity, modulating autophagy through PtdIns3P-dependent mechanisms 6. The protein participates in cancer cell migration and invasion by activating Rac1 GTPase through PtdIns5P production 7. In innate immunity, MTMR3 amplifies pattern recognition receptor-induced cytokine secretion by decreasing autophagy and increasing caspase-1 activation 8. Disease relevance: MTMR3 risk alleles associate with inflammatory bowel disease through enhanced innate immune responses 98, IgA nephropathy via increased TLR9-induced IgA immunity 10, and primary open-angle glaucoma as a protective factor 11. Elevated MTMR3 expression correlates with increased breast cancer risk 12. These findings highlight MTMR3's multifaceted role in autophagy, immunity, and cancer progression, making it a potential therapeutic target.