The Journal of biological chemistry
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Clinical Trial
The circulating glycosaminoglycan signature of respiratory failure in critically ill adults.
Systemic inflammatory illnesses (such as sepsis) are marked by degradation of the endothelial glycocalyx, a layer of glycosaminoglycans (including heparan sulfate, chondroitin sulfate, and hyaluronic acid) lining the vascular lumen. We hypothesized that different pathophysiologic insults would produce characteristic patterns of released glycocalyx fragments. We collected plasma from healthy donors as well as from subjects with respiratory failure due to altered mental status (intoxication, ischemic brain injury), indirect lung injury (non-pulmonary sepsis, pancreatitis), or direct lung injury (aspiration, pneumonia). ⋯ Plasma heparan sulfate concentrations directly correlated with intensive care unit length of stay. Serial plasma measurements performed in select patients revealed that circulating highly sulfated heparan fragments persisted for greater than 3 days after the onset of respiratory failure. Our findings demonstrate that circulating glycosaminoglycans are elevated in patterns characteristic of the etiology of respiratory failure and may serve as diagnostic and/or prognostic biomarkers of critical illness.
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Collapsin response mediator protein 2 (CRMP2) is traditionally viewed as an axonal growth protein involved in axon/dendrite specification. Here, we describe novel functions of CRMP2. A 15-amino acid peptide from CRMP2, fused to the TAT cell-penetrating motif of the HIV-1 protein, TAT-CBD3, but not CBD3 without TAT, attenuated N-methyl-d-aspartate receptor (NMDAR) activity and protected neurons against glutamate-induced Ca(2+) dysregulation, suggesting the key contribution of CRMP2 in these processes. ⋯ Moreover, CRMP2 down-regulation strongly attenuated TAT-CBD3-induced inhibition of reverse NCX. Overall, our results demonstrate that CRMP2 interacts with NCX and NMDAR and that TAT-CBD3 protects against glutamate-induced Ca(2+) dysregulation most likely via suppression of both NMDAR and NCX activities. Our results further clarify the mechanism of action of TAT-CBD3 and identify a novel regulatory checkpoint for NMDAR and NCX function based on CRMP2 interaction with these proteins.
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Dendritic cells (DC) play a critical role in modulating antigen-specific immune responses elicited by T cells via engagement of the prototypic T cell costimulatory receptor CD28 by the cognate ligands CD80/CD86, expressed on DC. Although CD28 signaling in T cell activation has been well characterized, it has only recently been shown that CD80/CD86, which have no demonstrated binding domains for signaling proteins in their cytoplasmic tails, nonetheless also transduce signals to the DC. Functionally, CD80/CD86 engagement results in DC production of the pro-inflammatory cytokine IL-6, which is necessary for full T cell activation. ⋯ Similar to IL-6, we have found that CD80/CD86-induced IDO production by DC at late time points is also dependent upon the PI3K → AKT → NF-κB pathway and requires cross-talk with NOTCH signaling. These data further suggest that the same signaling pathways downstream of DC CD80/CD86 cross-linking induce early IL-6 production to enhance T cell activation, followed by later IDO production to self-limit this activation. In addition to characterizing the pathways downstream of CD80/CD86 in IL-6 and IDO production, identification of a novel cross-talk between NOTCH1 and PI3K signaling may provide new insights in other biological processes where PI3K signaling plays a major role.
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The objective of the study was to examine the regulation of CCN2 by inflammatory cytokines, IL-1β, and TNF-α and to determine whether CCN2 modulates IL-1β-dependent catabolic gene expression in nucleus pulposus (NP) cells. IL-1β and TNF-α suppress CCN2 mRNA and protein expression in an NF-κB-dependent but MAPK-independent manner. The conserved κB sites located at -93/-86 and -546/-537 bp in the CCN2 promoter mediated this suppression. ⋯ Using disintegrins, echistatin, and VLO4, peptide inhibitors to αvβ3 and α5β1 integrins, we showed that CCN2 binding to both integrins was required for the inhibition of IL-1β-induced catabolic gene expression. It is noteworthy that analysis of human tissues showed a trend of altered expression of these integrins during degeneration. Taken together, these results suggest that CCN2 and inflammatory cytokines form a functional negative feedback loop in NP cells that may be important in the pathogenesis of disc disease.
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A pivotal step in canonical Wnt signaling is Wnt-induced β-catenin stabilization. In the absence of Wnt, β-catenin is targeted for β-transducin repeats-containing proteins (β-TrCP)-mediated degradation due to phosphorylation by glycogen synthase kinase 3 (Gsk3). How canonical Wnt signaling regulates Gsk3 to inhibit β-catenin proteolysis remains largely elusive. ⋯ We found that Wnt stimulation induced prolonged monoubiquitination of Gsk3β and Gsk3β-β-TrCP interaction. Monoubiquitination did not cause Gsk3β degradation nor affects its enzymatic activity. Rather, increased monoubiquitination of Gsk3β/Gsk3β-β-TrCP association suppressed β-catenin recruitment of β-TrCP, leading to long-term inhibition of β-catenin ubiquitination and degradation.