The Journal of biological chemistry
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Several neurological diseases, including Parkinson disease and dementia with Lewy bodies, are characterized by the accumulation of alpha-synuclein phosphorylated at Ser-129 (p-Ser-129). The kinase or kinases responsible for this phosphorylation have been the subject of intense investigation. Here we submit evidence that polo-like kinase 2 (PLK2, also known as serum-inducible kinase or SNK) is a principle contributor to alpha-synuclein phosphorylation at Ser-129 in neurons. ⋯ Inhibitors of PLK kinases inhibited alpha-synuclein phosphorylation both in primary cortical cell cultures and in mouse brain in vivo. Finally, specific knockdown of PLK2 expression by transduction with short hairpin RNA constructs or by knock-out of the plk2 gene reduced p-Ser-129 levels. These results indicate that PLK2 plays a critical role in alpha-synuclein phosphorylation in central nervous system.
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The induction of neurite retraction and growth cone collapse via G-protein-coupled receptors is involved in developmental as well as regenerative processes. The role of individual G-protein-mediated signaling processes in the regulation of neurite morphology is still incompletely understood. ⋯ Interestingly, the effects of lysophosphatidic acid were mediated mainly by G(13), whereas thrombin effects required G(12). Surprisingly, lack of Galpha(q)/Galpha(11) resulted in overshooting responses to both stimuli, indicating that G(q)/G(11)-mediated signaling most likely via activation of Rac antagonizes the effects of G(12)/G(13).
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Elafin is a neutrophil serine protease inhibitor expressed in lung and displaying anti-inflammatory and anti-bacterial properties. Previous studies demonstrated that some innate host defense molecules of the cystic fibrosis (CF) and chronic obstructive pulmonary disease airways are impaired due to increased proteolytic degradation observed during lung inflammation. In light of these findings, we thus focused on the status of elafin in CF lung. ⋯ However, NE in excess was shown to strongly diminish the ability of elafin to bind lipopolysaccharide (LPS) and its capacity to be immobilized by transglutamination. In conclusion, this study provides evidence that elafin is cleaved by its cognate enzyme NE present at excessive concentration in CF sputum and that P. aeruginosa infection promotes this effect. Such cleavage may have repercussions on the innate immune function of elafin.
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Sphingosine 1-Phosphate (S1P) modulates various cellular functions such as apoptosis, cell differentiation, and migration. Although S1P is an abundant signaling molecule in the central nervous system, very little is known about its influence on neuronal functions. We found that S1P concentrations were selectively decreased in the cerebrospinal fluid of adult rats in an acute and an inflammatory pain model. ⋯ By combining fluorescence resonance energy transfer (FRET)-based cAMP measurements with Multi Epitope Ligand Cartography (MELC), we showed that S1P decreased cAMP synthesis in excitatory dorsal horn neurons. Accordingly, intrathecal application of dihydro-S1P abolished the cAMP-dependent phosphorylation of NMDA receptors in the outer laminae of the spinal cord. Taken together, the data show that S1P modulates spinal nociceptive processing through inhibition of neuronal cAMP synthesis.
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Protein Z-dependent protease inhibitor (ZPI) is a recently identified member of the serpin superfamily that functions as a cofactor-dependent regulator of blood coagulation factors Xa (FXa) and XIa. Here we show that ZPI and its cofactor, protein Z (PZ), inhibit procoagulant membrane-bound factor Xa by the branched pathway acyl-intermediate trapping mechanism used by other serpins, but with significant variations of this mechanism that are unique to ZPI. Rapid kinetic analyses showed that the reaction proceeded by the initial assembly of a membrane-associated PZ-ZPI-FXa Michaelis complex (K(M) 53+/-5 nM) followed by conversion to a stable ZPI-FXa complex (k(lim) 1.2+/-0.1 s(-1)). ⋯ The ZPI-FXa complex was only transiently stable and dissociated with a rate constant that showed a bell-shaped pH dependence indicative of participation of factor Xa active-site residues. The complex was detectable by SDS-PAGE when denatured at low pH, consistent with it being a kinetically trapped covalent acyl-intermediate. Together our findings show that ZPI functions like other serpins to regulate the activity of FXa but in a manner uniquely dependent on protein Z, procoagulant membranes, and pH.