Lawrence MC, Borenstein-Auerbach N, McGlynn K, Kunnathodi F, Shahbazov R, Syed I, Kanak M, Takita M, Levy MF, Naziruddin B
Nuclear factor of activated T cells (NFAT) is activated by calcineurin in response to calcium signals derived by metabolic and inflammatory stress to regulate genes in pancreatic islets. Here we show that NFAT targets MAPKs, p300, and histone deacetylases (HDACs) to gene promoters to differentially regulate insulin and TNF-α genes. NFAT and ERK associated with the insulin gene promoter in response to GLP-1, while NFAT formed complexes with p38 and JNK upon promoters of the TNF-α gene in response to IL-1β. Translocation of NFAT and MAPKs to gene promoters was calcineurin/NFAT-dependent, and complex stability required MAPK activity. Knocking down NFATc2 expression, eliminating NFAT DNA binding sites, or interfering with NFAT nuclear import prevented association of MAPKs with gene promoters. Inhibiting p38 and JNK activity increased NFAT-ERK association with promoters, which repressed TNF-α and enhanced insulin gene expression. Moreover, inhibiting p38 and JNK induced a switch from NFAT-p38/JNK-p300 to NFAT-ERK-HDAC3 complex formation upon the TNF-α promoter, which resulted in gene repression. HAT/HDAC exchange was reversed on the insulin gene by p38/JNK inhibition in the presence of GLP-1, which enhanced gene expression. Overall, these data indicate that NFAT directs signaling enzymes to gene promoters in islets, which contribute to protein-DNA complex stability and promoter regulation. Furthermore, the data suggest that TNF-α can be repressed and insulin production can be enhanced by selectively targeting signaling components of NFAT-MAPK transcriptional/signaling complex formation in pancreatic β cells. These findings have therapeutic potential for suppressing islet inflammation while preserving islet function in diabetes and islet transplantation.