Prolyl Isomerase Pin1 Regulates Neuronal Differentiation via β-Catenin

Abstract

dThe Wnt/␤-catenin pathway promotes proliferation of neural progenitor cells (NPCs) at early stages and induces neuronal differentiation from NPCs at late stages, but the molecular mechanisms that control this stage-specific response are unclear. Pin1 is a prolyl isomerase that regulates cell signaling uniquely by controlling protein conformation after phosphorylation, but its role in neuronal differentiation is not known. Here we found that whereas Pin1 depletion suppresses neuronal differentiation, Pin1 overexpression enhances it, without any effects on gliogenesis from NPCs in vitro. Consequently, Pin1-null mice have significantly fewer upper layer neurons in the motor cortex and severely impaired motor activity during the neonatal stage. A proteomic approach identified ␤-catenin as a major substrate for Pin1 in NPCs, in which Pin1 stabilizes ␤-catenin. As a result, Pin1 knockout leads to reduced ␤-catenin during differentiation but not proliferation of NPCs in developing brains. Importantly, defective neuronal differentiation in Pin1 knockout NPCs is fully rescued in vitro by overexpression of ␤-catenin but not a ␤-catenin mutant that fails to act as a Pin1 substrate. These results show that Pin1 is a novel regulator of NPC differentiation by acting on ␤-catenin and provides a new postphosphorylation signaling mechanism to regulate developmental stage-specific functioning of ␤-catenin signaling in neuronal differentiation. N eurons are generated from neural stem/progenitor cells (NPCs) during brain development. Recently, it has been emerging that an array of extracellular factors, including Wnt, platelet-derived growth factor, vascular endothelial growth factor, and bone morphogenic proteins, trigger signaling cascades leading to activation of downstream transcription factors to regulate neuronal differentiation from NPCs (6,16,18,22,23,33,51,68,86,91). However, little is known about how these signaling pathways are integrated to control the highly ordered events of neuronal differentiation to generate neurons in different layers or subregions of the brain during development.A well-established key signaling pathway in neurogenesis is the Wnt/␤-catenin pathway (13,16,18,22,46,62). For example, overexpression of constitutively active ␤-catenin in NPCs induces neurogenesis and increases cortical size (12,23,90). Similarly, overexpression of Wnt3 increases neurogenesis in cortical progenitor cells (26, 43) and adult hippocampal stem/progenitor cells (34). Conversely, ablation of ␤-catenin inhibits neurogenesis, leading to reduced brain size (23, 90). Finally, activation of the Wnt/␤-catenin pathway leads to the formation of ␤-catenin-TCF complexes to transactivate Wnt target genes, including many proneural transcription factors (25,30,48,79). Significantly, the in vivo function of Wnt/␤-catenin signaling in neuronal differentiation depends on the developmental stage during brain development. It appears to promote proliferation of early NPCs (expansion phase) but induces neuronal differentiation of NPCs in the la...

Prolyl isomerase Pin1 and protein kinase HIPK2 cooperate to promote cortical neurogenesis by suppressing Groucho/TLE:Hes1-mediated inhibition of neuronal differentiation

“…The same effects were observed after silencing of Pin1 in cortical progenitor cells using lentiviral-mediated expression of a Pin1 short hairpin (sh) RNA reagent, but not when a control non-silencing shRNA was used (Figure 1g). Taken together with the demonstration that knockout of mouse Pin1 causes decreased neuronal differentiation in cultured cortical progenitor cells, 25 these results show that Pin1 promotes cortical neurogenesis. Moreover, they provide evidence that Gro/TLE1:Hes1 and Pin1 have opposite biological functions during cortical neuronal development.…”

“…Pharmacological inhibition, or shRNA-mediated silencing, of Pin1 activity in cortical progenitor cells causes decreased neuronal differentiation and increased numbers of cells expressing markers of the undifferentiated neural progenitor state, in agreement with recent studies showing that Pin1 knockout in mice decreases neuronal differentiation in cultured neural progenitor cells. 25 More importantly, we have shown that expression of Pin1 and HIPK2 blocks the ability of Gro/ TLE1:Hes1 to inhibit neuronal differentiation in both retinoic acid-treated SH-SY5Y neuroblastoma cells and primary cultures of cortical neural progenitor cells.…”

Differential Regulation of Cellular Senescence and Differentiation by Prolyl Isomerase Pin1 in Cardiac Progenitor Cells

“…Pin1 also modulates several other signaling molecules involved in cell fate determination. By stabilizing ␤-catenin Pin1 induces neuronal differentiation of neural progenitor cells (16). A strong correlation between Pin1 expression and Notch activity has also been reported implicating Notch as a substrate mediating effects of Pin1 signaling and regulating proliferation and lineage commitment (17).…”

“…Lineage commitment and cell differentiation that are highly relevant in the context of stem cells are also dramatically influenced by Pin1. Pin1 maintains the balance between stem cell pluripotency, stemness, and commitment by stabilizing and activating molecules controlling self-renewal and differentiation (15)(16)(17). These provocative roles of Pin1 in the areas of proliferation, survival, senescence, and cell fate determination have tremendous impact on stem cell biology that remains unexplored in the context of CPCs.…”

C-terminal domain small phosphatase 1 and MAP kinase reciprocally control REST stability and neuronal differentiation

“…In vivo, Pin1 becomes highly expressed in nestin-positive neural progenitors between embryonic days E12.5 and E15.5 (37), precisely the time at which REST is down-regulated in cortical progenitors (3). Further, premature loss of Pin1 in mice, using nestin-driven Cre recombinase, results in fewer βIII tubulin positive neurons in the developing cerebral cortex (37). The authors proposed that Pin1 is required to stabilize β-catenin and thereby terminate expression of Wnt-activated proneural genes, such as neurogenin 1.…”