Substance P Induces Rapid and Transient Membrane Blebbing in U373MG Cells in a p21-Activated Kinase-Dependent Manner

U373MG astrocytoma cells endogenously express the full-length neurokinin 1 receptor (NK1R). Substance P (SP), the natural ligand for NK1R, triggers rapid and transient membrane blebbing and we report that these morphological changes have different dynamics and intracellular signaling as compared to the changes that we have previously described in HEK293-NK1R cells. In both cell lines, the SP-induced morphological changes are Gq-independent, and they require the Rho, Rho-associated coiled-coil kinase (ROCK) signaling pathway. Using confocal microscopy we have demonstrated that tubulin is phosphorylated subsequent to cell stimulation with SP and that tubulin accumulates inside the blebs. Colchicine, a tubulin polymerization inhibitor, blocked SP-induced blebbing in U373MG but not in HEK293-NK1R cells. Although p21-activated kinase (PAK) is expressed in both cell lines, SP induced rapid phosphorylation of PAK in U373MG, but failed to phosphorylate PAK in HEK293-NK1R cells. The cell-permeable Rho inhibitor C3 transferase inhibited SP-induced PAK phosphorylation, but the ROCK inhibitor Y27632 had no effect on PAK phosphorylation, suggesting that Rho activates PAK in a ROCK-independent manner. Our study demonstrates that SP triggers rapid changes in cell morphology mediated by distinct intracellular signaling mechanisms in U373MG versus HEK293-NK1R cells

QUANTITATIVE ANALYSIS OF CARBON BLACK AGGLOMERATES MORPHOLOGY IN ELASTOMER COMPOSITES BASED ON X-RAY TOMOGRAPHY BY MEANS OF NUMERICAL CLUSTERING

International audienceABSTRACT A novel methodology for characterizing the morphology distribution of filler agglomerates in elastomer composites is presented based on laboratory-sourced X-ray tomography. Various feature extraction methods (via, e.g., image-processing filters, segmentation) and selection tools (Spearman's rank correlation coefficient) combined with K-means unsupervised clustering algorithm were developed for identifying the distinct morphological classes in model materials (carbon-filled ethylene propylene diene monomer rubber). The interest of this methodology was demonstrated by precisely differentiating the materials compounded with different processing parameters. For instance, in this example, thanks to this analysis, it was found that introducing the filler before the elastomer in internal mixer tends to favor more structured agglomerates