Pressure overload and prolonged angiotensin II (Ang II) infusion elicit cardiac hypertrophy in Ang II receptor 1 (AT₁) null mouse, whereas Ang II receptor 2 (AT₂) gene deletion abolishes the hypertrophic response. The roles and signals of the cardiac AT₂ receptor still remain unsettled. Promyelocytic leukemia zinc finger protein (PLZF) was shown to bind to the AT₂ receptor and transmit the hypertrophic signal. Using PLZF knockout mice we directed our studies on the function of PLZF concerning the cardiac specific transcription factor GATA4, and GATA4 targets.

PLZF knockout and age-matched wild-type (WT) mice were treated with Ang II, infused at a rate of 4.2 ng·kg⁻¹·min⁻¹ for 3 weeks. Ang II elevated systolic blood pressure to comparable levels in PLZF knockout and WT mice (140 mmHg). WT mice developed prominent cardiac hypertrophy and fibrosis after Ang II infusion. In contrast, there was no obvious cardiac hypertrophy or fibrosis in PLZF knockout mice. An AT₂ receptor blocker given to Ang II-infused wild type mice prevented hypertrophy, verifying the role of AT₂ receptor for cardiac hypertrophy. Chromatin immunoprecipitation and electrophoretic mobility shift assay showed that PLZF bound to the GATA4 gene regulatory region. A Luciferase assay verified that PLZF up-regulated GATA4 gene expression and the absence of PLZF expression in vivo produced a corresponding repression of GATA4 protein.

PLZF is an important AT₂ receptor binding protein in mediating Ang II induced cardiac hypertrophy through an AT₂ receptor-dependent signal pathway. The angiotensin II-AT₂-PLZF-GATA4 signal may further augment Ang II induced pathological effects on cardiomyocytes.