{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nMTMR3 is a member of the myotubularin family of phosphoinositide phosphatases that regulate the cellular levels of phosphoinositide messengers. It contains a catalytic domain, an N‐terminal PH‑GRAM module that preferentially binds phosphatidylinositol 5‑phosphate, and a C‑terminal FYVE domain that is atypical—being dispensable for its in vitro enzymatic activity and not conferring classical endosomal localization. Structural studies, including crystallographic analysis of the PH‑GRAM–phosphatase portion, have provided insight into its membrane‐targeting and regulatory properties."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nMTMR3 also plays pivotal roles in controlling autophagy and cell migration. Overexpression of a dominant-negative mutant of MTMR3 triggers autophagosome formation by locally elevating PtdIns3P and recruiting PtdIns3P-binding autophagy effectors, whereas the wild-type protein limits nascent autophagosome size and reduces net autophagic flux. In conjunction with the lipid kinase PIKfyve, MTMR3 helps produce PtdIns5P that in turn promotes Rac1 activation and cell motility. Moreover, MTMR3 interacts with the mTORC1 complex to negatively regulate its activity, adding another layer to its role in coordinating membrane dynamics and nutrient-responsive signaling."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "8"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its classical functions in lipid regulation, MTMR3 is implicated in multiple additional cellular processes that impact both cell division and disease. It forms heterodimeric complexes with MTMR4 to regulate cytokinetic abscission via interactions with mitotic kinases and scaffold proteins, ensuring proper daughter cell separation. In innate immune cells, heightened MTMR3 expression decreases local phosphatidylinositol 3‑phosphate and autophagic activity, thereby amplifying pattern recognition receptor–induced caspase‑1 activation and cytokine secretion. In the context of cancer, reduced MTMR3 expression—via microRNA-mediated downregulation—leads to enhanced NF‑κB and Wnt/β‑catenin signaling and contributes to tumor progression, while direct silencing in breast cancer cells induces S‑phase arrest and autophagy. Finally, genetic and mechanistic studies have linked MTMR3 variants or promoter activity to IgA nephropathy susceptibility and hinted at interplay with long noncoding RNAs (such as HULC) in modulating breast cancer cell behavior."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "9", "end_ref": "16"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "J Laporte, F Blondeau, A Buj-Bello, et al. 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