Circ-CAMTA1 regulated by Ca2+ influx inhibited pyruvate carboxylase activity and modulate T cell function in patients with systemic lupus erythematosus

The expression profiles of circRNAs in Jurkats cells, co-cultured with and without ionomycin, were analyzed by next-generation sequencing and validated using real-time polymerase chain reaction. The identified Ca2+ influx-regulated circRNAs were further examined in T cells from 42 patients with SLE and 23 healthy controls. The biological function of specific circRNAs was investigated using transfection and RNA pull-down assay. After validation, we confirmed that the expression levels of circ-ERCC4, circ-NFATC2, circ-MYH10, circ-CAMTA1, circ-ASH1L, circ-SOCS7, and circ-ASAP1 were consistently increased in Jurkat cells following Ca2+ influx. The expression levels of circ-CAMTA1, circ-ASH1L, and circ-ASAP1 were significantly lower in T cells from patients with SLE, with even lower levels observed in those with higher disease activity. Interferon (IFN)-α was found to suppress the expression of circ-CAMTA1. Circ-CAMTA1 bound to pyruvate carboxylase and inhibited its biologic activity. Overexpression of circ-CAMTA1, but not its linear form, significantly decreased extracellular glucose levels. Furthermore, increased expression of circ-CAMTA1, but not its linear form, enhanced IL-2 secretion and the protein expression of NFAT1.