{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nPPP1R2, also known as inhibitor‐2 (I-2), plays a multifaceted regulatory role in cellular homeostasis by modulating protein phosphatase-1 (PP1) activity. It acts as a key component of regulatory complexes at centrosomes and membranes, where it associates indirectly with kinases such as Nek2 and KPI-2 to enhance kinase activity through localized PP1 inhibition. This modulation is essential for proper centrosome separation and accurate cell cycle progression. In cardiomyocytes, gene transfer of PPP1R2 ameliorates heart failure progression by fine-tuning PP1 activity and enhancing contractile function, while its overexpression disrupts centrosome number and midbody architecture, implicating it directly in the fidelity of cell division."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nDuring mitosis, PPP1R2 localizes to critical structures such as the spindle, midzone, and midbody, where it ensures proper chromosome segregation and completion of cytokinesis. Loss of its function leads to mitotic errors including supernumerary centrosomes, multipolar spindles, and impaired cytokinesis—all of which underscore its role in maintaining accurate cell division. Moreover, PPP1R2 forms higher-order complexes with regulators like Pin1, altering Pin1’s substrate specificity and reinforcing a network of interdependent interactions between phosphatases and kinases (notably Aurora B) that are essential for mitotic progression."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nThe activity of PPP1R2 itself is finely regulated by phosphorylation events mediated by kinases such as glycogen synthase kinase-3β (GSK3β) and casein kinase 2. These modifications determine its inhibitory potency towards PP1 and its subsequent impact on downstream targets, including the regulation of GSK3 dephosphorylation, which in turn affects levels of proteins such as SERCA2. Additionally, a similar inhibitor activity resembling PPP1R2 is observed in spermatozoa, where it participates in the control of motility, and the presence of multiple pseudogenes within the PPP1R2 family attests to its evolutionary conservation and regulatory significance. A potential link to the regulation of microtubule acetylation in primary cilia has also been suggested, although it remains to be fully elucidated."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "7", "end_ref": "11"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Masumi Eto, Elizabeth Elliott, Todd D Prickett, et al. 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