Abstract
Type I protein kinase A (PKA) is targeted to the TCR-proximal signaling machinery by the A-kinase anchoring protein ezrin and negatively regulates T cell immune function through activation of the C-terminal Src kinase. RI anchoring disruptor (RIAD) is a high-affinity competitor peptide that specifically displaces type I PKA from A-kinase anchoring proteins. In this study, we disrupted type I PKA anchoring in peripheral T cells by expressing a soluble ezrin fragment with RIAD inserted in place of the endogenous A-kinase binding domain under the lck distal promoter in mice. Peripheral T cells from mice expressing the RIAD fusion protein (RIAD-transgenic mice) displayed augmented basal and TCR-activated signaling, enhanced T cell responsiveness assessed as IL-2 secretion, and reduced sensitivity to PGE(2)- and cAMP-mediated inhibition of T cell function. Hyperactivation of the cAMP-type I PKA pathway is involved in the T cell dysfunction of HIV infection, as well as murine AIDS, a disease model induced by infection of C57BL/6 mice with LP-BM5, a mixture of attenuated murine leukemia viruses. LP-BM5-infected RIAD-transgenic mice resist progression of murine AIDS and have improved viral control. This underscores the cAMP-type I PKA pathway in T cells as a putative target for therapeutic intervention in immunodeficiency diseases.