Targeting GATA4 for cardiac repair

Abstract

Various strategies have been applied to replace the loss of cardiomyocytes in order to restore reduced cardiac function and prevent the progression of heart disease. Intensive research efforts in the field of cellular reprogramming and cell transplantation may eventually lead to efficient in vivo applications for the treatment of cardiac injuries, representing a novel treatment strategy for regenerative medicine. Modulation of cardiac transcription factor (TF) networks by chemical entities represents another viable option for therapeutic interventions. Comprehensive screening projects have revealed a number of molecular entities acting on molecular pathways highly critical for cellular lineage commitment and differentiation, including compounds targeting Wnt- and transforming growth factor beta (TGFβ)-signaling. Furthermore, previous studies have demonstrated that GATA4 and NKX2-5 are essential TFs in gene regulation of cardiac development and hypertrophy. For example, both of these TFs are required to fully activate mechanical stretch-responsive genes such as atrial natriuretic peptide and brain natriuretic peptide (BNP). We have previously reported that the compound 3i-1000 efficiently inhibited the synergy of the GATA4-NKX2-5 interaction. Cellular effects of 3i-1000 have been further characterized in a number of confirmatory in vitro bioassays, including rat cardiac myocytes and animal models of ischemic injury and angiotensin II-induced pressure overload, suggesting the potential for small molecule-induced cardioprotection.

Keywords: medicinal chemistry; protein function; transcription factors; transcriptional regulation.

Figure 1

Variable DNA‐binding modes of GATA‐proteins. (a) Opposite DNA‐binding of C‐terminal zinc fingers of GATA3 (PDB, 3DFX), (b) adjacent DNA‐binding of C‐terminal zinc fingers of GATA3 (PDB, 3DFV), (c) both N‐ and C‐terminal zinc fingers of GATA1 bound to palindromic DNA recognition site (PDB, 3VD6), (d) both N‐ and C‐terminal zinc fingers of GATA3 bind on different DNA molecules, thereby bridging two independent and separate DNA fragments suggesting a mechanisms of DNA looping and long‐range gene regulation. This finding was confirmed in solution by an in‐gel fluorescence resonance energy transfer analysis (PDB, 4HC7)14

Figure 2

Cardiac protein association map derived from the STRING database illustrates the network of interactions for selected TFs; GATA4, NKX2‐5, MEF2C, HAND2, SRF, and TBX5. The associations are intended to be specific and meaningful, and thus, proteins jointly contribute to the shared functions. Interaction map color codes; blue indicates direct binding, purple indicates post‐translational modifications, yellow indicates transcriptional regulation, black indicates reaction, green arrow indicates activation and grey indicates the protein's indirect contribution to shared functions. Abbreviations: BMP4, bone morphogenetic protein 4 and HOPX, HOP homeodomain; FOS, FBJ murine osteosarcoma viral oncogene homolog; GATA4, GATA binding protein 4; HAND2, heart and neural crest derivatives expressed 2; MAPK7, mitogen‐activated protein kinase 7; MAPK14, mitogen‐activated protein kinase 14; MEF2C, myocyte enhancer factor 2C; MKL1, megakaryoblastic leukemia 1; MYOCD, myocardin; MYOD1, myogenic differentiation 1; MYOG, myogenin; NKX2‐5, NK2 homeobox 5; SRF, serum response factor; TBX5, T‐box 5; ZFPM2, zinc finger protein, multitype 2 (also known as FOG2)

Figure 3

Cardiac transcriptional activity is regulated by interplay of the GATA4 transcription factor with several other TFs and post‐translational modifications. The vast majority of the protein associations of GATA4 are mediated by the C‐terminal zinc finger, while the N‐terminal zinc finger is responsible for interactions with the friend of GATA2 (FOG2). Cardiac specific heterotypic interactions and DNA occupation preferences for pair‐wise GATA4 ensembles are categorized based on experimental measurements of the protein and DNA binding modes. Specific context‐dependent GATA4 protein subconsortiums regulate both the commitment of stem cells toward the cardiac fate and hypertrophic gene expression in mature cardiac cells. Abbreviations: Acet., acetylation; GATA4, GATA binding protein 4; HAND2, heart and neural crest derivatives expressed 2; MEF2C, myocyte enhancer factor 2C; NKE, NK2 element; NKX2‐5, NK2 homeobox 5; Phos., phosphorylation; PTM, post‐translational modification; SRE, serum response element; SRF, serum response factor; Sumo/Ubi, sumoylation/ubiquitination; TBX5, T‐box 5