17 research outputs found

    A self-inhibitory interaction within Nup155 and membrane binding are required for nuclear pore complex formation

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    Nuclear pore complexes (NPCs) are gateways through the nuclear envelope. How they form into a structure containing three rings and integrate into the nuclear envelope remains a challenging paradigm for coordinated assembly of macro-complexes. In vertebrates, the cytoplasmic and nucleoplasmic rings of NPCs are mostly formed by multiple copies of the Nup107-Nup160 complex, whereas the central, or inner ring is composed of Nup53, Nup93, Nup155 and the two paralogues Nup188 and Nup205. Inner ring assembly is only partially understood. Using in vitro nuclear assembly reactions, we show that direct pore membrane binding of Nup155 is crucial for NPC formation. Replacing full-length Nup155 with its N-terminal β-propeller allows assembly of the outer ring components to the NPC backbone that also contains Nup53. However, further assembly, especially recruitment of the Nup93 and Nup62 complexes, is blocked. Self-interaction between the N- and C-terminal domains of Nup155 has an auto-inhibitory function that prevents interaction between the N-terminus of Nup155 and the C-terminal region of Nup53. Nup93 can overcome this block by binding to Nup53, thereby promoting formation of the inner ring and the NPC

    Macrophage migration inhibitory factor (MIF) promotes fibroblast migration in scratch-wounded monolayers in vitro

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    AbstractMIF was recently redefined as an inflammatory cytokine, which functions as a critical mediator of diseases such as septic shock, rheumatoid arthritis, atherosclerosis, and cancer. MIF also regulates wound healing processes. Given that fibroblast migration is a central event in wound healing and that MIF was recently demonstrated to promote leukocyte migration through an interaction with G-protein-coupled receptors, we investigated the effect of MIF on fibroblast migration in wounded monolayers in vitro. Transient but not permanent exposure of primary mouse or human fibroblasts with MIF significantly promoted wound closure, a response that encompassed both a proliferative and a pro-migratory component. Importantly, MIF-induced fibroblast activation was accompanied by an induction of calcium signalling, whereas chronic exposure with MIF down-regulated the calcium transient, suggesting receptor desensitization as the underlying mechanism

    Cardioprotection through S-nitros(yl)ation of macrophage migration inhibitory factor

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    Background—Macrophage migration inhibitory factor (MIF) is a structurally unique inflammatory cytokine that controls cellular signaling in human physiology and disease through extra- and intracellular processes. Macrophage migration inhibitory factor has been shown to mediate both disease-exacerbating and beneficial effects, but the underlying mechanism(s) controlling these diverse functions are poorly understood. Methods and Results—Here, we have identified an S-nitros(yl)ation modification of MIF that regulates the protective functional phenotype of MIF in myocardial reperfusion injury. Macrophage migration inhibitory factor contains 3 cysteine (Cys) residues; using recombinant wtMIF and site-specific MIF mutants, we have identified that Cys-81 is modified by S-nitros(yl)ation whereas the CXXC-derived Cys residues of MIF remained unaffected. The selective S-nitrosothiol formation at Cys-81 led to a doubling of the oxidoreductase activity of MIF. Importantly, S-nitrosothiol-MIF formation was measured both in vitro and in vivo and led to a decrease in cardiomyocyte apoptosis in the reperfused heart. This decrease was paralleled by a S-nitrosothiol-MIF– but not Cys81 serine (Ser)–MIF mutant–dependent reduction of infarct size in an in vivo model of myocardial ischemia/reperfusion injury. Conclusions—S-nitros(yl)ation of MIF is a pivotal novel regulatory mechanism, providing enhanced activity resulting in increased cytoprotection in myocardial reperfusion injury.10 page(s
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