Project description:The chemokine CXCL12 and its receptor CXCR4 play important roles in signaling and migration of T-cells, but little is known about the transcriptional events involved in CXCL12-mediated T-cell migration. In this study we performed microarray analysis on CXCL12- treated T-cells, and found that the Wnt family of proteins was significantly upregulated during CXCL12 treatment. Confirmation of these results by real-time PCR and Western analysis indicated that the non-canonical Wnt pathway was specifically upregulated during CXCL12 treatment. In vitro and in vivo knockdown studies confirm that b-catenin (the key mediator of canonical Wnt signaling) is not involved in the CXCL12-mediated migration of T-cells. However, Wnt5A, a non-canonical Wnt protein, increases signaling through the CXCL12/ CXCR4 axis via Protein Kinase C (PKC). Our results demonstrated that CXCL12 required Wnt5A to mediate T-cell migration, and the treatment of T-cells with recombinant Wnt5A sensitized T-cells to CXCL12 induced migration. Additionally, Wnt5A expression was required for the sustained expression of CXCR4, both transcriptionally and translationally. These results could be translated in vivo, using EL4 thymoma metastasis as a model of T-cell migration. Taken together our data indicate, for the first time, that Wnt5A is a critical mediator of the CXCL12/ CXCR4 signaling axis. Experiment Overall Design: Primary T cells were treated with human CXCL12 (Peprotech, Rocky Hill, NJ) at 100 ng/ml per 10 million cells overnight in a humidified incubator at 37ÂºC with 5% CO2. Control cells were incubated in media only. Cells were harvested and washed with ice cold PBS for 2 times followed by the addition of ice cold TRIzol (Invitrogen, Carlsbad, CA) and frozen at -80ÂºC overnight. Total RNA was isolated using the RNA isolation kit manufactured by Qiagen (Valencia, CA). The cDNA was prepared from equal amount of RNA using a cDNA preparation kit (Bio-Rad, Hercules, CA) followed by preparation of cRNA according to manufacturerâs instructions (Agilent, Santa Clara, CA). The cRNA was amplified and labeled with either Cy-3 or Cy-5, using the Agilent low-input linear amplification kit, according to manufacturerâs protocols. Labeled cRNA were applied to the Human 44K whole genome oligo array slides (Agilent, Santa Clara, CA). Slides were hybridized in a rotating chamber overnight at 60ÂºC in 6X SSC. Next day, slides were washed with 0.005% Triton X-102 for 10 minutes, and then in 0.1X SSC, 0.005% Triton X-102 for 5 minutes on ice. Slides were dried using a nitrogen-filled air gun, and scanned using an Agilent scanner. Images were analyzed using the Agilent Feature Extractor Software, Version A.7.5.1 and ratios for each spot were calculated.

Project description:Apoptosis plays a pivotal role in embryogenesis and postnatal cell homeostasis, involving DNA or subcellular fragmentation, and shedding of small membranous microvesicles termed apoptotic bodies (AB). Following DNA damage, hypoxia, or vascular injury, the chemokine CXCL12 has been implicated in the recruitment of progenitor cells for tissue regeneration through its receptor CXCR4 and in mechanisms counteracting apoptosis. Whether AB deliver alarm signals for regenerative responses to neighbouring cells beyond recruitment or eat-me signals for phagocytes and relevance to diseases with abundant apoptosis, eg atherosclerosis, remains unknown. Here we show that endothelial cell-derived AB are generated during diet-induced atherosclerosis and can be transferred to recipient endothelial or smooth muscle cells to induce functional expression of CXCL12. This is mediated through miRNA-126 enriched in AB, which acts by silencing RGS16 translation and unlocking CXCR4 to unleash an auto-regulatory feedback loop inducing CXCL12. Injection of AB promoted mobilization and incorporation of progenitor cells, reducing diet-induced atherosclerosis in apolipoprotein E-deficient mice, and local transfer of microRNA-126 inhibited collar-induced arterial plaque formation. This was associated with increased smooth muscle content but decreased macrophage and apoptotic cell content, all features of plaque stability. Our data identify a new mechanism, by which AB confer microRNA-126 as a paracrine alarm messenger to enhance CXCR4 signals and CXCL12 expression, thereby limiting or repairing vascular damage. This adds to the important functions of microRNAs in health and disease and may extend to progenitor cell recruitment during other forms of tissue repair or homeostasis. AB were isolated from supernatants of apoptotic, serum-starved human umbilical vein endothelial cells (HUVECs) by sequential centrifugation steps. Total RNA was isolated from AB or HUVECs and microRNA was purified using the mirVanaTM miRNA Isolation Kit (Ambion). microRNA obtained from 10 µg of total RNA was labeled using the mirVanaTM miRNA Labeling Kit (Ambion) and fluorescent Cy3 (Molecular Probes), and hybridized to the Ambion mirVanaTM miRNA Bioarray (1566 v.1). Hybridized mirVana miRNA Bioarrays were scanned and quantified by using ImaGene 5.5.4 (Bio Discovery). Resulted signal intensities were background corrected and then normalized using variance stabilization normalization. (Huber, 2002).

Project description:Nathaniel L. Coggins, Danielle Trakimas, S. Laura Chang, Anna Ehrlich, Paramita Ray, Kathryn E. Luker, Jennifer J. Linderman & Gary D. Luker. CXCR7 controls competition for recruitment of β-arrestin 2 in cells expressing both CXCR4 and CXCR7. PLoS ONE 9, 6 (2014). Chemokine CXCL12 promotes growth and metastasis of more than 20 different human cancers, as well as pathogenesis of other common diseases. CXCL12 binds two different receptors, CXCR4 and CXCR7, both of which recruit and signal through the cytosolic adapter protein β-arrestin 2. Differences in CXCL12-dependent recruitment of β-arrestin 2 in cells expressing one or both receptors remain poorly defined. To quantitatively investigate parameters controlling association of β-arrestin 2 with CXCR4 or CXCR7 in cells co-expressing both receptors, we used a systems biology approach combining real-time, multi-spectral luciferase complementation imaging with computational modeling. Cells expressing only CXCR4 maintain low basal association with β-arrestin 2, and CXCL12 induces a rapid, transient increase in this interaction. In contrast, cells expressing only CXCR7 have higher basal association with β-arrestin 2 and exhibit more gradual, prolonged recruitment of β-arrestin 2 in response to CXCL12. We developed and fit a data-driven computational model for association of either CXCR4 or CXCR7 with β-arrestin 2 in cells expressing only one type of receptor. We then experimentally validated model predictions that co-expression of CXCR4 and CXCR7 on the same cell substantially decreases both the magnitude and duration of CXCL12-regulated recruitment of β-arrestin 2 to CXCR4. Co-expression of both receptors on the same cell only minimally alters recruitment of β-arrestin 2 to CXCR7. In silico experiments also identified β-arrestin 2 as a limiting factor in cells expressing both receptors, establishing that CXCR7 wins the "competition" with CXCR4 for CXCL12 and recruitment of β-arrestin 2. These results reveal how competition for β-arrestin 2 controls integrated responses to CXCL12 in cells expressing both CXCR4 and CXCR7. These results advance understanding of normal and pathologic functions of CXCL12, which is critical for developing effective strategies to target these pathways therapeutically.

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