Here, we define an endothelial cell (EC) lumen signaling complex involving Cdc42, Par6b, Par3, junction adhesion molecule (Jam)-B and Jam-C, membrane type 1-matrix metalloproteinase (MT1-MMP), and integrin ␣ 2 ␤ 1 , which coassociate to control human EC tubulogenesis in 3D collagen matrices. Blockade of both Jam-B and Jam-C using antibodies, siRNA, or dominant-negative mutants completely interferes with lumen and tube formation resulting from a lack of Cdc42 activation, inhibition of Cdc42-GTP-dependent signal transduction, and blockade of MT1-MMP-dependent proteolysis. This process requires interdependent Cdc42 and MT1-MMP signaling, which involves Par3 binding to the Jam-B and Jam-C cytoplasmic tails, an interaction that is necessary to physically couple the components of the lumen signaling complex. MT1-MMP proteolytic activity is necessary for Cdc42 activation during EC tube formation in 3D collagen matrices but not on 2D collagen surfaces, whereas Cdc42 activation is necessary for MT1-MMP to create vascular guidance tunnels and tube networks in 3D matrices through proteolytic events. This work reveals a novel interdependent role for Cdc42-dependent signaling and MT1-MMP-dependent proteolysis, a process that occurs selectively in 3D collagen matrices and that requires EC lumen signaling complexes, to control human EC tubulogenesis during vascular morphogenesis. (Blood. 2010;115(25):5259-5269) IntroductionRecent work has lead to an increased understanding of how endothelial and epithelial cells make lumens and tubes in 3D extracellular matrices. [1][2][3][4][5][6][7][8][9] Key regulators of lumen formation include Cdc42, which was first shown to regulate this process in endothelial cells (ECs), [10][11][12] and later in epithelial cells. 13,14 Components of the cell polarity machinery including Par3, Par6, and PKC control lumen formation of both cell types. 6,11,[13][14][15] Furthermore, we recently reported that Cdc42 activates a signaling cascade involving PKC⑀, Pak2, Pak4, Src, Yes, B-Raf, C-Raf, and Erk1/2 to control this process. 12,16 In addition, EC-directed cellsurface proteolytic events through membrane type 1-matrix metalloproteinase (MT1-MMP) 17,18 controls EC lumen and vascular guidance tunnel formation in 3D collagen matrices. 19,20 A key question that has remained unresolved is how Cdc42-dependent signaling and MT1-MMP-dependent proteolysis are functionally coupled to regulate EC tube formation. 2 Recent studies have revealed that MT1-MMP directs 3D matrix-specific events in relationship to tumor motility, cellular differentiation, and morphogenesis. 2,21 We have shown that both tumor cell and EC invasion of 3D collagen matrices requires MT1-MMP, but not motility on 2D collagen substrates. 19,22 Interestingly, adipocyte differentiation occurs in an MT1-MMP-dependent manner in 3D matrices but not on 2D matrix surfaces, 23 and MT1-MMP controls the 3D-specific process of EC lumen and tube formation. 18,19 Thus, MT1-MMP is functionally linked to critical cellular events that specifically occur in 3D...

In this study, we present data showing that Cdc42-dependent lumen formation by endothelial cells (ECs) in three-dimensional (3D) collagen matrices involves coordinated signaling by PKCϵ in conjunction with the Src-family kinases (SFKs) Src and Yes. Activated SFKs interact with Cdc42 in multiprotein signaling complexes that require PKCϵ during this process. Src and Yes are differentially expressed during EC lumen formation and siRNA suppression of either kinase, but not Fyn or Lyn, results in significant inhibition of EC lumen formation. Concurrent with Cdc42 activation, PKCϵ- and SFK-dependent signaling converge to activate p21-activated kinase (Pak)2 and Pak4 in steps that are also required for EC lumen formation. Pak2 and Pak4 further activate two Raf kinases, B-Raf and C-Raf, leading to ERK1 and ERK2 (ERK1/2) activation, which all seem to be necessary for EC lumen formation. This work reveals a multicomponent kinase signaling pathway downstream of integrin-matrix interactions and Cdc42 activation involving PKCϵ, Src, Yes, Pak2, Pak4, B-Raf, C-Raf and ERK1/2 to control EC lumen formation in 3D collagen matrices.

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The detection of novel signals in the auditory scene is an elementary task of any hearing system. In Neoconocephalus katydids, a primary auditory interneuron (TN-1) with broad spectral sensitivity, responded preferentially to rare deviant pulses (7 pulses/s repetition rate) embedded among common standard pulses (140 pulses/s repetition rate). Eliminating inhibitory input did not affect the detection of the deviant pulses. Detection thresholds for deviant pulses increased significantly with increasing amplitude of standard pulses. Responses to deviant pulses occurred when the carrier frequencies of deviant and standard were sufficiently different, both when the deviant had a higher or lower carrier frequency than the standard. Recordings from receptor neurons revealed that TN-1 responses to the deviant pulses did not depend on the population response strength of the receptors, but on the distribution of the receptor cell activity. TN-1 responses to the deviant pulse occurred only when the standard and deviant pulses were transmitted by different groups of receptor cells. TN-1 responses parallel stimulus specific adaptation (SSA) described in mammalian auditory system. The results support the hypothesis that the mechanisms underlying SSA and change-detection are located in the TN-1 dendrite, rather than the receptor cells.

BackgroundEcotoxicological studies on the insensitive munitions formulation IMX-101 and its components 2,4-dinitroanisole (DNAN), nitroguanidine (NQ) and nitrotriazolone (NTO) in various organisms showed that DNAN was the main contributor to the overall toxicity of IMX-101 and suggested that the three compounds acted independently. These results motivated this toxicogenomics study to discern toxicological mechanisms for these compounds at the molecular level.MethodsHere we used the soil nematode Caenorhabditis elegans, a well-characterized genomics model, as the test organism and a species-specific, transcriptome-wide 44 K-oligo probe microarray for gene expression analysis. In addition to the control treatment, C. elegans were exposed for 24 h to 6 concentrations of DNAN (1.95–62.5 ppm) or NQ (83–2667 ppm) or 5 concentrations of NTO (187–3000 ppm) with ten replicates per treatment. The nematodes were transferred to a clean environment after exposure. Reproduction endpoints (egg and larvae counts) were measured at three time points (i.e., 24-, 48- and 72-h). Gene expression profiling was performed immediately after 24-h exposure to each chemical at the lowest, medium and highest concentrations plus the control with four replicates per treatment.ResultsStatistical analyses indicated that chemical treatment did not significantly affect nematode reproduction but did induce 2175, 378, and 118 differentially expressed genes (DEGs) in NQ-, DNAN-, and NTO-treated nematodes, respectively. Bioinformatic analysis indicated that the three compounds shared both DEGs and DEG-mapped Reactome pathways. Gene set enrichment analysis further demonstrated that DNAN and NTO significantly altered 12 and 6 KEGG pathways, separately, with three pathways in common. NTO mainly affected carbohydrate, amino acid and xenobiotics metabolism while DNAN disrupted protein processing, ABC transporters and several signal transduction pathways. NQ-induced DEGs were mapped to a wide variety of metabolism, cell cycle, immune system and extracellular matrix organization pathways.ConclusionDespite the absence of significant effects on apical reproduction endpoints, DNAN, NTO and NQ caused significant alterations in gene expression and pathways at 1.95 ppm, 187 ppm and 83 ppm, respectively. This study provided supporting evidence that the three chemicals may exert independent toxicity by acting on distinct molecular targets and pathways.Electronic supplementary materialThe online version of this article (10.1186/s12918-018-0636-0) contains supplementary material, which is available to authorized users.