{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nPPP1R1B encodes the multifunctional protein DARPP‐32 and its truncated isoform t‐DARPP, which have emerged as pivotal regulators in both neuronal signaling and oncogenesis. In the brain, DARPP‐32 functions as an integrator of dopaminergic and glutamatergic inputs in dopaminoceptive neurons, modulating protein phosphatase‐1 (PP1) activity and thereby fine‐tuning downstream signaling cascades. Genetic variation in PPP1R1B impacts mRNA expression of its isoforms and is associated with alterations in frontostriatal circuitry, cognitive performance, and risk for schizophrenia and other neuropsychiatric disorders. Moreover, studies have demonstrated that DARPP‐32 is important not only for synaptic plasticity and the modulation of learning strategies but also for the age‐dependent maintenance of cognitive functions, further underscoring its broad role in brain physiology and disease."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "7"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to its critical functions in the central nervous system, aberrant expression and alternative splicing of PPP1R1B play central roles in several cancers. Gene locus amplification and overexpression of DARPP‐32 and/or t‐DARPP have been documented in gastric, breast, and esophageal carcinomas, where these proteins confer oncogenic properties such as anti‐apoptotic activity, enhanced cell migration, and resistance to therapeutic agents (for example, trastuzumab in ERBB2‐amplified breast cancers). Mechanistically, t‐DARPP activates Akt signaling, upregulates survival proteins like Bcl2, and modulates receptor tyrosine kinase pathways—including those mediated by IGF1R and DDR1—to promote tumor cell survival and alter invasive behavior. These studies collectively indicate that DARPP‐32 isoforms serve as key nodes linking growth factor signals to intracellular survival and motility programs."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "14"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAt the molecular level, DARPP‐32’s function is governed by its phosphorylation status, which determines whether it acts as an inhibitor of PP1 or influences other signaling partners, such as the transcription factor CREB. In addition, emerging evidence reveals that DARPP‐32 can interact directly with splicing factors to regulate pre‐mRNA processing, thereby linking extracellular signaling to gene regulatory mechanisms. Such regulatory versatility—affecting everything from early sensory selection and synaptic plasticity in neurons to modulation of apoptotic pathways and cellular invasiveness in tumors—underscores the broad biological impact of PPP1R1B variations and highlights its potential as a therapeutic target in both neuropsychiatric disorders and cancer."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "15", "end_ref": "17"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Andreas Meyer-Lindenberg, Richard E Straub, Barbara K Lipska, et al. 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