title: cAMP-dependent protein kinase A (PKA) signaling induces TNFR1 exosome-like vesicle release via anchoring of PKA regulatory subunit RIIbeta to BIG2.
abstract: The 55-kDa TNFR1 (type I tumor necrosis factor receptor) can be released to the extracellular space by two mechanisms, the proteolytic cleavage and shedding of soluble receptor ectodomains and the release of full-length receptors within exosome-like vesicles. We have shown that the brefeldin A-inhibited guanine nucleotide exchange protein BIG2 associates with TNFR1 and selectively modulates the release of TNFR1 exosome-like vesicles via an ARF1- and ARF3-dependent mechanism. Here, we assessed the role of BIG2 A kinase-anchoring protein (AKAP) domains in the regulation of TNFR1 exosome-like vesicle release from human vascular endothelial cells. We show that 8-bromo-cyclic AMP induced the release of full-length, 55-kDa TNFR1 within exosome-like vesicles via a protein kinase A (PKA)-dependent mechanism. Using RNA interference to decrease specifically the levels of individual PKA regulatory subunits, we demonstrate that RIIbeta modulates both the constitutive and cAMP-induced release of TNFR1 exosome-like vesicles. Consistent with its AKAP function, BIG2 was required for the cAMP-induced PKA-dependent release of TNFR1 exosome-like vesicles via a mechanism that involved the binding of RIIbeta to BIG2 AKAP domains B and C. We conclude that both the constitutive and cAMP-induced release of TNFR1 exosome-like vesicles occur via PKA-dependent pathways that are regulated by the anchoring of RIIbeta to BIG2 via AKAP domains B and C. Thus, BIG2 regulates TNFR1 exosome-like vesicle release by two distinct mechanisms, as a guanine nucleotide exchange protein that activates class I ADP-ribosylation factors and as an AKAP for RIIbeta that localizes PKA signaling within cellular TNFR1 trafficking pathways.
authors.affiliation: Pulmonary and Vascular Medicine Branch, Bethesda, Maryland 20892-1590.
authors.forename: Aminul
authors.initials: A
authors.lastname: Islam
authors.affiliation: Translational Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1590.
authors.forename: Heather
authors.initials: H
authors.lastname: Jones
authors.affiliation: Translational Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1590.
authors.forename: Toyoko
authors.initials: T
authors.lastname: Hiroi
authors.affiliation: Pulmonary and Vascular Medicine Branch, Bethesda, Maryland 20892-1590.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lam
authors.affiliation: Pulmonary and Vascular Medicine Branch, Bethesda, Maryland 20892-1590.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Translational Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1590.
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.affiliation: Translational Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1590.
authors.forename: Martha
authors.initials: M
authors.lastname: Vaughan
authors.affiliation: Pulmonary and Vascular Medicine Branch, Bethesda, Maryland 20892-1590. Electronic address: levines@nhlbi.nih.gov.
authors.forename: Stewart J
authors.initials: SJ
authors.lastname: Levine
mesh_terms: D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D058966:Contactins; D003470:Culture Media / Q000378:metabolism; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D017434:Protein Structure, Tertiary; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C098304:CNTN4 protein, human; D015816:Cell Adhesion Molecules, Neuronal; D058966:Contactins; D003470:Culture Media; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D020662:Guanine Nucleotide Exchange Factors; D047888:Receptors, Tumor Necrosis Factor, Type I; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases