Induction of Wnt signaling antagonists and p21-activated kinase enhances cardiomyocyte proliferation during zebrafish heart regeneration

Abstract

Heart regeneration occurs by dedifferentiation and proliferation of pre-existing cardiomyocytes (CMs). However, the signaling mechanisms by which injury induces CM renewal remain incompletely understood. Here, we find that cardiac injury in zebrafish induces expression of the secreted Wnt inhibitors, including Dickkopf 1 (Dkk1), Dkk3, secreted Frizzled-related protein 1 (sFrp1), and sFrp2, in cardiac tissue adjacent to injury sites. Experimental blocking of Wnt activity via Dkk1 overexpression enhances CM proliferation and heart regeneration, whereas ectopic activation of Wnt8 signaling blunts injury-induced CM dedifferentiation and proliferation. Although Wnt signaling is dampened upon injury, the cytoplasmic β-catenin is unexpectedly increased at disarrayed CM sarcomeres in myocardial wound edges. Our analyses indicated that P21-activated kinase 2 (Pak2) is induced at regenerating CMs, where it phosphorylates cytoplasmic β-catenin at Ser675 and increases its stability at disassembled sarcomeres during regeneration. Myocardial-specific induction of the phospho-mimetic β-catenin (S675E) enhances CM dedifferentiation and sarcomere disassembly in response to cardiac damage. Importantly, inactivation of Pak2 kinase activity reduces the Ser675-phosphorylated β-catenin (pS675-β-catenin) at cardiac wounds and attenuates CM sarcomere disorganization, dedifferentiation, and proliferation. Taken together, these findings demonstrate that coordination of Wnt signaling inhibition and Pak2/pS675-β-catenin signaling enhances zebrafish heart regeneration by supporting CM dedifferentiation and proliferation.

Origin and function of activated fibroblast states during zebrafish heart regeneration

“…On the one hand, Wnt is generally considered to be a proproliferative factor, and Wnt activation has been shown to be beneficial for zebrafish fin and spinal cord regeneration 33,45 . On the other hand, the role of Wnt signalling in cardiomyocyte dedifferentiation and proliferation is controversial [46][47][48] . We hypothesized that Wnt might exert its complex functions by regulating activation of proregenerative cell states, and we investigated whether cells with a shared lineage origin exhibited similar changes following a stimulus, that is, whether lineage relationship is predictive of perturbation response.…”

Phosphoproteomic Analysis Reveals Downstream PKA Effectors of AKAP Cypher/ZASP in the Pathogenesis of Dilated Cardiomyopathy

“…Activated β-catenin is closely linked to cell proliferation ( 24 , 29 ). To explore the role of Cypher in cardiomyocyte proliferation, RT-qPCR for cell cycle-related genes was performed on both untreated and Cypher siRNA-treated H9C2 cells.…”

“…Activated β-catenin promotes biological processes such as proliferation, angiogenesis, metastasis, and apoptosis inhibition ( 24 – 26 ). Phosphorylation of β-catenin at Ser675 was reported to activate β-catenin and enhance cardiomyocyte proliferation ( 29 ). We observed that cardiomyocyte proliferation was suppressed by Cypher deficiency ( Figures 5F–J ), which is consistent with the “regulation of cell proliferation” enrichment in GO annotation for downregulated proteins ( Figure 2D ).…”

Identification of inflammatory response and alternative splicing in acute kidney injury and experimental verification of the involvement of RNA‑binding protein RBFOX1 in this disease

“…CSNK1A1, PAK2, and IKBKB have serine/threonine protein kinase activity and play an important role in intracellular signal transduction. Studies have demonstrated that CSNK1A1 and PAK2 phosphorylate β-catenin at Ser45 and Ser675, respectively, thereby inhibiting the WNT signaling pathway ( 39 , 40 ). IKBKB regulates the immune response by inducing IkB-a phosphorylation at Ser32 and Ser36 through the classical activation pathway to promote NF-κB signal transduction ( 41 ).…”