Convergence of Protein Kinase C and JAK-STAT signaling on transcription factor GATA-4

Abstract

Angiotensin II (AII), a potent vasoactive hormone, acts on numerous organs via G-protein-coupled receptors and elicits cell-specific responses. At the level of the heart, AII stimulation alters gene transcription and leads to cardiomyocyte hypertrophy. Numerous intracellular signaling pathways are activated in this process; however, which of these directly link receptor activation to transcriptional regulation remains undefined. We used the ANF gene (NPPA) as marker to elucidate the signaling cascades involved in AII transcriptional responses. We show that ANF transcription is activated directly by the AII type 1 receptor and precedes the development of myocyte hypertrophy. This response maps to a STAT and GATA binding sites and the two elements transcriptionally cooperate to mediate signaling through JAK-STAT and PKC-GATA-4 pathways. PKC phosphorylation enhances GATA-4 DNA binding activity and STAT-1 functionally and physically interacts with GATA-4 to synergistically activate AII and other growth factor-inducible promoters. Moreover, GATA factors are able to recruit STAT proteins to target promoters via GATA binding sites which are sufficient to support synergy. Thus, STAT proteins can act as growth factor inducible coactivators of tissuespecific transcription factors. Interactions between STAT and GATA proteins may provide a general paradigm to understand cell specificity of cytokines and growth factors signaling.