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Phenotypic Effects of Homeodomain-Interacting Protein Kinase 2 Deletion in Mice.

ABSTRACT: Homeodomain-interacting protein kinase 2 (HIPK2) is a serine-threonine kinase that phosphorylates various transcriptional and chromatin regulators, thus modulating numerous important cellular processes, such as proliferation, apoptosis, DNA damage response, and oxidative stress. The role of HIPK2 in the pathogenesis of cancer and fibrosis is well established, and evidence of its involvement in the homeostasis of multiple organs has been recently emerging. We have previously demonstrated that Hipk2-null (Hipk2-KO) mice present cerebellar alterations associated with psychomotor abnormalities and that the double ablation of HIPK2 and its interactor HMGA1 causes perinatal death due to respiratory failure. To identify other alterations caused by the loss of HIPK2, we performed a systematic morphological analysis of Hipk2-KO mice. Post-mortem examinations and histological analysis revealed that Hipk2 ablation causes neuronal loss, neuronal morphological alterations, and satellitosis throughout the whole central nervous system (CNS); a myopathic phenotype characterized by variable fiber size, mitochondrial proliferation, sarcoplasmic inclusions, morphological alterations at neuromuscular junctions; and a cardiac phenotype characterized by fibrosis and cardiomyocyte hypertrophy. These data demonstrate the importance of HIPK2 in the physiology of skeletal and cardiac muscles and of different parts of the CNS, thus suggesting its potential relevance for different new aspects of human pathology.

SUBMITTER: De Biase D

PROVIDER: S-EPMC8348407 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Runt-related transcription factor 2 (Runx2) and muscle segment homeobox homolog 2-interacting nuclear target (MINT) (Spen homolog) are transcriptional regulators critical for mammalian development. MINT enhances Runx2 activation of osteocalcin (OC) fibroblast growth factor (FGF) response element in an FGF2-dependent fashion in C3H10T1/2 cells. Although the MINT N-terminal RNA recognition motif domain contributes, the muscle segment homeobox homolog 2-interacting domain is sufficient for Runx2 activation. Intriguingly, Runx1 cannot replace Runx2 in this assay. To better understand this Runx2 signaling cascade, we performed structure-function analysis of the Runx2-MINT trans-activation relationship. Systematic truncation and domain swapping in Runx1:Runx2 chimeras identified that the unique Runx2 activation domain 3 (AD3), encompassed by residues 316-421, conveys MINT+FGF2 trans-activation in transfection assays. Ala mutagenesis of Runx2 Ser/Thr residues identified that S301 and T326 in AD3 are necessary for full MINT+FGF2 trans-activation. Conversely, phosphomimetic Asp substitution of these AD3 Ser/Thr residues enhanced activation by MINT. Adjacent Pro residues implicated regulation by a proline-directed protein kinase (PDPK). Systematic screening with PDPK inhibitors identified that the casein kinase-2/homeodomain-interacting protein kinase (HIPK)/dual specificity tyrosine phosphorylation regulated kinase inhibitor 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT), but not ERK, c-Jun N-terminal kinase, p38MAPK, or other casein kinase-2 inhibitors, abrogated Runx2-, MINT-, and FGF2-activation. Systematic small interfering RNA-mediated silencing of DMAT-inhibited PDPKs revealed that HIPK3 depletion reduced MINT+FGF2-dependent activation of Runx2. HIPK3 and Runx2 coprecipitate after in vitro transcription-translation, and recombinant HIPK3 recognizes Runx2 AD3 as kinase substrate. Furthermore, DMAT treatment and HIPK3 RNAi inhibited MINT+FGF2 activation of Runx2 AD3, and nuclear HIPK3 colocalized with MINT. HIPK3 antisense oligodeoxynucleotide selectively reduced Runx2 protein accumulation and OC gene expression in C3H10T1/2 cells. Thus, HIPK3 participates in MINT+FGF2 regulation of Runx2 AD3 activity and controls Runx2-dependent OC expression.

Project description:BACKGROUND:Cardiac kinases play a critical role in the development of heart failure, and represent potential tractable therapeutic targets. However, only a very small fraction of the cardiac kinome has been investigated. To identify novel cardiac kinases involved in heart failure, we used an integrated transcriptomics and bioinformatics analysis and identified Homeodomain-Interacting Protein Kinase 2 (HIPK2) as a novel candidate kinase. The role of HIPK2 in cardiac biology is unknown. METHODS:We used the Expression2Kinase algorithm for the screening of kinase targets. To determine the role of HIPK2 in the heart, we generated cardiomyocyte (CM)-specific HIPK2 knockout and heterozygous mice. Heart function was examined by echocardiography, and related cellular and molecular mechanisms were examined. Adeno-associated virus serotype 9 carrying cardiac-specific constitutively active MEK1 (TnT-MEK1-CA) was administrated to rescue cardiac dysfunction in CM-HIPK2 knockout mice. RESULTS:To our knowledge, this is the first study to define the role of HIPK2 in cardiac biology. Using multiple HIPK2 loss-of-function mouse models, we demonstrated that reduction of HIPK2 in CMs leads to cardiac dysfunction, suggesting a causal role in heart failure. It is important to note that cardiac dysfunction in HIPK2 knockout mice developed with advancing age, but not during development. In addition, CM-HIPK2 knockout mice and CM-HIPK2 heterozygous mice exhibited a gene dose-response relationship of CM-HIPK2 on heart function. HIPK2 expression in the heart was significantly reduced in human end-stage ischemic cardiomyopathy in comparison to nonfailing myocardium, suggesting a clinical relevance of HIPK2 in cardiac biology. In vitro studies with neonatal rat ventricular CMscorroborated the in vivo findings. Specifically, adenovirus-mediated overexpression of HIPK2 suppressed the expression of heart failure markers, NPPA and NPPB, at basal condition and abolished phenylephrine-induced pathological gene expression. An array of mechanistic studies revealed impaired extracellular signal-regulated kinase 1/2 signaling in HIPK2-deficient hearts. An in vivo rescue experiment with adeno-associated virus serotype 9 TnT-MEK1-CA nearly abolished the detrimental phenotype of knockout mice, suggesting that impaired extracellular signal-regulated kinase signaling mediated apoptosis as the key factor driving the detrimental phenotype in CM-HIPK2 knockout mice hearts. CONCLUSIONS:Taken together, these findings suggest that CM-HIPK2 is required to maintain normal cardiac function via extracellular signal-regulated kinase signaling.

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Phenotypic Effects of Homeodomain-Interacting Protein Kinase 2 Deletion in Mice.

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