The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Carole A. Parent - One of the best experts on this subject based on the ideXlab platform.

  • retraction exosomes mediate ltb4 release during Neutrophil Chemotaxis
    PLOS Biology, 2021
    Co-Authors: Ritankar Majumdar, Aidin Tavakoli Tameh, Carole A. Parent
    Abstract:

    Leukotriene B4 (LTB4) is secreted by chemotactic Neutrophils, forming a secondary gradient that amplifies the reach of primary chemoattractants. This strategy increases the recruitment range for Neutrophils and is important during inflammation. Here, we show that LTB4 and its synthesizing enzymes localize to intracellular multivesicular bodies that, upon stimulation, release their content as exosomes. Purified exosomes can activate resting Neutrophils and elicit chemotactic activity in a LTB4 receptor-dependent manner. Inhibition of exosome release leads to loss of directional motility with concomitant loss of LTB4 release. Our findings establish that the exosomal pool of LTB4 acts in an autocrine fashion to sensitize Neutrophils towards the primary chemoattractant, and in a paracrine fashion to mediate the recruitment of neighboring Neutrophils in trans. We envision that this mechanism is used by other signals to foster communication between cells in harsh extracellular environments.

  • The LTB4-BLT1 axis regulates the polarized trafficking of chemoattractant GPCRs during Neutrophil Chemotaxis.
    Journal of cell science, 2018
    Co-Authors: Bhagawat C. Subramanian, Konstadinos Moissoglu, Carole A. Parent
    Abstract:

    Neutrophils sense and respond to diverse chemotactic cues through G-protein-coupled receptors (GPCRs). However, the precise trafficking dynamics of chemoattractant GPCRs during Neutrophil activation and Chemotaxis remain unclear. Here, by using small-molecule inhibitors and CRISPR-based knockouts, we establish that two primary chemoattractant GPCRs - formyl peptide receptor 1 (FPR1) and complement component 5a (C5a) receptor 1 (C5aR1) - internalize in a CDC42-actin-dependent manner. Through live-cell imaging, we demonstrate that, upon stimulation, FPR1 rapidly clusters and re-distributes along the plasma membrane to the trailing edge, where it internalizes and is directionally trafficked towards the front of migrating primary human Neutrophils. In contrast to FPR1 and C5aR1, the leukotriene B4 (LTB4) receptor (BLT1, also known as LTB4R), which relays LTB4 signals in response to primary chemoattractants during Neutrophil Chemotaxis, fails to internalize upon physiological stimulation with LTB4, N-formyl-Met-Leu-Phe (fMLF) or C5a. Importantly, we report that blocking the LTB4-BLT1 axis or downstream myosin activation enhances the internalization of FPR1 and C5aR1, thus reducing downstream signaling and impairing Chemotaxis to primary chemoattractants. The polarized trafficking of chemoattractant GPCRs and its regulation by the BLT1-mediated myosin activation therefore drives persistent chemotactic signaling in Neutrophils.This article has an associated First Person interview with the first author of the paper.

  • exosomes mediate ltb4 release during Neutrophil Chemotaxis
    PLOS Biology, 2016
    Co-Authors: Ritankar Majumdar, Aidin Tavakoli Tameh, Carole A. Parent
    Abstract:

    Leukotriene B4 (LTB4) is secreted by chemotactic Neutrophils, forming a secondary gradient that amplifies the reach of primary chemoattractants. This strategy increases the recruitment range for Neutrophils and is important during inflammation. Here, we show that LTB4 and its synthesizing enzymes localize to intracellular multivesicular bodies that, upon stimulation, release their content as exosomes. Purified exosomes can activate resting Neutrophils and elicit chemotactic activity in a LTB4 receptor-dependent manner. Inhibition of exosome release leads to loss of directional motility with concomitant loss of LTB4 release. Our findings establish that the exosomal pool of LTB4 acts in an autocrine fashion to sensitize Neutrophils towards the primary chemoattractant, and in a paracrine fashion to mediate the recruitment of neighboring Neutrophils in trans. We envision that this mechanism is used by other signals to foster communication between cells in harsh extracellular environments.

  • discoidin domain receptor 2 regulates Neutrophil Chemotaxis in 3d collagen matrices
    Blood, 2013
    Co-Authors: Philippe V Afonso, Colin Mccann, Senta M Kapnick, Carole A. Parent
    Abstract:

    Neutrophils express a variety of collagen receptors at their surface, yet their functional significance remains unclear. Although integrins are essential for Neutrophil adhesion and migration on 2-dimensional (2D) surfaces, Neutrophils can compensate for the absence of integrins in 3-dimensional (3D) lattices. In contrast, we demonstrate that the inhibition of the tyrosine-kinase collagen receptor discoidin domain receptor 2 (DDR2) has no impact on human primary Neutrophil migration on 2D surfaces but is an important regulator of Neutrophil Chemotaxis in 3D collagen matrices. In this context, we show that DDR2 activation specifically regulates the directional migration of Neutrophils in chemoattractant gradients. We further demonstrate that DDR2 regulates directionality through its ability to increase secretion of metalloproteinases and local generation of collagen-derived chemotactic peptide gradients. Our findings highlight the importance of collagen-derived extracellular signaling during Neutrophil Chemotaxis in 3D matrices.

  • ltb4 is a signal relay molecule during Neutrophil Chemotaxis
    Developmental Cell, 2012
    Co-Authors: Philippe V Afonso, Colin Mccann, Mirkka Jankajunttila, Charlotte M Oliver, Khaled A Aamer, Wolfgang Losert, Marcus T Cicerone, Carole A. Parent
    Abstract:

    Summary Neutrophil recruitment to inflammation sites purportedly depends on sequential waves of chemoattractants. Current models propose that leukotriene B 4 (LTB 4 ), a secondary chemoattractant secreted by Neutrophils in response to primary chemoattractants such as formyl peptides, is important in initiating the inflammation process. In this study we demonstrate that LTB 4 plays a central role in Neutrophil activation and migration to formyl peptides. We show that LTB 4  production dramatically amplifies formyl peptide-mediated Neutrophil polarization and Chemotaxis by regulating specific signaling pathways acting upstream of actin polymerization and MyoII phosphorylation. Importantly, by analyzing the migration of Neutrophils isolated from wild-type mice and mice lacking the formyl peptide receptor 1, we demonstrate that LTB 4 acts as a signal to relay information from cell to cell over long distances. Together, our findings imply that LTB 4 is a signal-relay molecule that exquisitely regulates Neutrophil Chemotaxis to formyl peptides, which are produced at the core of inflammation sites.

Wolfgang G. Junger - One of the best experts on this subject based on the ideXlab platform.

  • mtor and differential activation of mitochondria orchestrate Neutrophil Chemotaxis
    Journal of Cell Biology, 2015
    Co-Authors: Carola Ledderose, Amelie F Graf, Bianca Brix, Theresa Birsak, Jingping Zhang, Wolfgang G. Junger
    Abstract:

    Neutrophils use Chemotaxis to locate invading bacteria. Adenosine triphosphate (ATP) release and autocrine purinergic signaling via P2Y2 receptors at the front and A2a receptors at the back of cells regulate Chemotaxis. Here, we examined the intracellular mechanisms that control these opposing signaling mechanisms. We found that mitochondria deliver ATP that stimulates P2Y2 receptors in response to chemotactic cues, and that P2Y2 receptors promote mTOR signaling, which augments mitochondrial activity near the front of cells. Blocking mTOR signaling with rapamycin or PP242 or mitochondrial ATP production (e.g., with CCCP) reduced mitochondrial Ca2+ uptake and membrane potential, and impaired cellular ATP release and Neutrophil Chemotaxis. Autocrine stimulation of A2a receptors causes cyclic adenosine monophosphate accumulation at the back of cells, which inhibits mTOR signaling and mitochondrial activity, resulting in uropod retraction. We conclude that mitochondrial, purinergic, and mTOR signaling regulates Neutrophil Chemotaxis and may be a pharmacological target in inflammatory diseases.

  • ecto nucleoside triphosphate diphosphohydrolase 1 e ntpdase1 cd39 regulates Neutrophil Chemotaxis by hydrolyzing released atp to adenosine
    Journal of Biological Chemistry, 2008
    Co-Authors: Ross Corriden, Wolfgang G. Junger, Simon C Robson, Yu Chen, Yoshiaki Inoue, Guido Beldi, Paul A Insel
    Abstract:

    Polymorphonuclear Neutrophils release ATP in response to stimulation by chemoattractants, such as the peptide N-formyl-methionyl-leucyl-phenylalanine. Released ATP and the hydrolytic product adenosine regulate Chemotaxis of Neutrophils by sequentially activating purinergic nucleotide and adenosine receptors, respectively. Here we show that that ecto-nucleoside triphosphate diphosphohydrolase 1 (E-NTPDase1, CD39) is a critical enzyme for hydrolysis of released ATP by Neutrophils and for cell migration in response to multiple agonists (N-formyl-methionyl-leucyl-phenylalanine, interleukin-8, and C5a). Upon stimulation of human Neutrophils or differentiated HL-60 cells in a chemotactic gradient, E-NTPDase1 tightly associates with the leading edge of polarized cells during Chemotaxis. Inhibition of E-NTPDase1 reduces the migration speed of Neutrophils but not their ability to detect the orientation of the gradient field. Studies of Neutrophils from E-NTPDase1 knock-out mice reveal similar impairments of Chemotaxis in vitro and in vivo. Thus, E-NTPDase1 plays an important role in regulating Neutrophil Chemotaxis by facilitating the hydrolysis of extracellular ATP.

  • Purinergic regulation of Neutrophil Chemotaxis.
    Cellular and Molecular Life Sciences, 2008
    Co-Authors: Wolfgang G. Junger
    Abstract:

    Chemotaxis allows polymorphonuclear Neutrophils (PMN) to rapidly reach infected and inflamed sites. However, excessive influx of PMN damages host tissues. Better knowledge of the mechanisms that control PMN Chemotaxis may lead to improved treatments of inflammatory diseases. Recent findings suggest that ATP and adenosine are involved in PMN Chemotaxis. Therefore, these purinergic signaling processes may be suitable targets for novel therapeutic approaches to ameliorate host tissue damage.

  • atp release guides Neutrophil Chemotaxis via p2y2 and a3 receptors
    Science, 2006
    Co-Authors: Yu Chen, Ross Corriden, Yoshiaki Inoue, Paul A Insel, Naoyuki Hashiguchi, Annelies S Zinkernagel, Victor Nizet, Wolfgang G. Junger
    Abstract:

    Cells must amplify external signals to orient and migrate in chemotactic gradient fields. We find that human Neutrophils release adenosine triphosphate (ATP) from the leading edge of the cell surface to amplify chemotactic signals and direct cell orientation by feedback through P2Y2 nucleotide receptors. Neutrophils rapidly hydrolyze released ATP to adenosine that then acts via A3-type adenosine receptors, which are recruited to the leading edge, to promote cell migration. Thus, ATP release and autocrine feedback through P2Y2 and A3 receptors provide signal amplification, controlling gradient sensing and migration of Neutrophils.

Christy L Haynes - One of the best experts on this subject based on the ideXlab platform.

  • the role of p38 mapk in Neutrophil functions single cell Chemotaxis and surface marker expression
    Analyst, 2013
    Co-Authors: Donghyuk Kim, Christy L Haynes
    Abstract:

    Neutrophils act as the first line of defence in the human immune system by migrating to the site of abnormal events and performing their designated roles. One major signalling pathway that drives Neutrophil action in vivo is the p38 mitogen-activated protein kinase (MAPK)-dependent pathway. Herein, a microfluidic platform is employed to explore the mechanistic role of p38 MAPK in Neutrophil Chemotaxis. Neutrophils, with and without p38 MAPK inhibition, were exposed to pairwise competing gradients of Chemotaxis-inducing molecules. Overall, p38 MAPK inhibitor-treated Neutrophils were still capable of moving toward a chemoattractant signal; however, the hierarchy of Neutrophil response to various chemoattractants changed and there was more deviation from direct movement toward a chemoattractant signal in p38 MAPK-blocked cells. In a parallel fluorescence imaging study, Neutrophil expression of surface receptors (CXCR1, FPR2, BLTR, CD11b and CD66b) changed when comparing untreated and p38 MAPK-blocked cells. All results demonstrate that the p38 MAPK-dependent pathway plays a critical role in Neutrophil Chemotaxis and this role is, in part, through the regulation of surface receptor expression. These data regarding how receptor expression and Chemotaxis are influenced by the p38 MAPK pathways lend insight into Neutrophil behaviour in physiological environments and the potential manipulation of p38 MAPK for therapeutic purposes.

  • Neutrophil Chemotaxis within a competing gradient of chemoattractants
    Analytical Chemistry, 2012
    Co-Authors: Donghyuk Kim, Christy L Haynes
    Abstract:

    The dynamics of Neutrophil Chemotaxis under competing chemoattractant gradients was studied using a microfluidic platform. This microfluidic platform, which establishes a stable and dynamic gradient of chemoattractants across a cell culture chamber, enabled the investigation of human Neutrophil migration patterns in the presences of four different chemoattractants (leukotriene B4, chemokine C–X–C motif ligands 2 and 8, and fMLP) and competing gradients of all pairwise combinations. The migration patterns for individual cells were tracked and quantitatively analyzed, and the results suggest a hierarchy among these chemoattractants of fMLP > CXCL8 > CXCL2 > leukotriene B4. In all conditions, over 60% of Neutrophils exposed to a competing gradient move toward the stronger signal though the weaker chemoattractant still influences Neutrophil motility. These results yield insight about how each chemoattractant contributes to overall Neutrophil Chemotaxis within complex physiological environments.

Anna Huttenlocher - One of the best experts on this subject based on the ideXlab platform.

  • MicroRNA Overexpression screen reveals a noncanonical role of CDK2 in regulating Neutrophil migration
    2019
    Co-Authors: Alan Y. Hsu, Anna Huttenlocher, Diane R. Wang, Sheng Liu, Ramizah Syahirah, David A. Bennin, David M. Umulis, Jun Wan, Qing Deng
    Abstract:

    Abstract Neutrophil migration is essential for inflammatory responses to kill pathogens, however it also causes tissue injury. To discover novel therapeutic targets that modulate Neutrophil migration, we performed a Neutrophil-specific microRNA overexpression screen in zebrafish, and identified eight microRNAs as potent suppressors of Neutrophil migration. Among those, miR-199 decreases Neutrophil Chemotaxis in zebrafish and human Neutrophil-like cells. Intriguingly, in terminally differentiated Neutrophils, miR-199 alters the cell cycle-related pathways and directly suppresses cyclin-dependent kinase 2 (cdk2), whose known activity is restricted to cell cycle progression and cell differentiation. Inhibiting CDK2, but not DNA replication, disrupts cell polarity and Chemotaxis of zebrafish Neutrophils. Chemotaxis of primary human Neutrophils are also reduced by CDK2 inhibition. Furthermore, miR-199 overexpression or CDK2 inhibition significantly improves the outcome of lethal systemic inflammation challenges in zebrafish. Together, our results reveal previously unknown functions of miR-199 and CDK2 in regulating Neutrophil migration and provide new directions in alleviating systemic inflammation. One Sentence Summary miR-199 directly suppresses cdk2 expression, Neutrophil Chemotaxis and systemic inflammation.

  • characterizing asthma from a drop of blood using Neutrophil Chemotaxis
    Proceedings of the National Academy of Sciences of the United States of America, 2014
    Co-Authors: Eric K Sackmann, Anna Huttenlocher, Erwin Berthier, Elizabeth A Schwantes, Paul S Fichtinger, Michael D Evans, Laura Dziadzio, Sameer K Mathur, David J Beebe
    Abstract:

    Asthma is a chronic inflammatory disorder that affects more than 300 million people worldwide. Asthma management would benefit from additional tools that establish biomarkers to identify phenotypes of asthma. We present a microfluidic solution that discriminates asthma from allergic rhinitis based on a patient's Neutrophil chemotactic function. The handheld diagnostic device sorts Neutrophils from whole blood within 5 min, and generates a gradient of chemoattractant in the microchannels by placing a lid with chemoattractant onto the base of the device. This technology was used in a clinical setting to assay 34 asthmatic (n = 23) and nonasthmatic, allergic rhinitis (n = 11) patients to establish domains for asthma diagnosis based on Neutrophil Chemotaxis. We determined that Neutrophils from asthmatic patients migrate significantly more slowly toward the chemoattractant compared with nonasthmatic patients (P = 0.002). Analysis of the receiver operator characteristics of the patient data revealed that using a Chemotaxis velocity of 1.55 μm/min for asthma yields a diagnostic sensitivity and specificity of 96% and 73%, respectively. This study identifies Neutrophil Chemotaxis velocity as a potential biomarker for asthma, and we demonstrate a microfluidic technology that was used in a clinical setting to perform these measurements.

  • microfluidic kit on a lid a versatile platform for Neutrophil Chemotaxis assays
    Blood, 2012
    Co-Authors: Eric K Sackmann, Anna Huttenlocher, Erwin Berthier, Edmond W K Young, Miriam A Shelef, Sarah A Wernimont, David J Beebe
    Abstract:

    Improvements in Neutrophil Chemotaxis assays have advanced our understanding of the mechanisms of Neutrophil recruitment; however, traditional methods limit biologic inquiry in important areas. We report a microfluidic technology that enables Neutrophil purification and Chemotaxis on-chip within minutes, using nanoliters of whole blood, and only requires a micropipette to operate. The low sample volume requirements and novel lid-based method for initiating the gradient of chemoattractant enabled the measurement of human Neutrophil migration on a cell monolayer to probe the adherent and migratory states of Neutrophils under inflammatory conditions; mouse Neutrophil Chemotaxis without sacrificing the animal; and both 2D and 3D Neutrophil Chemotaxis. First, the Neutrophil Chemotaxis on endothelial cells revealed 2 distinct Neutrophil phenotypes, showing that endothelial cell-Neutrophil interactions influence Neutrophil chemotactic behavior. Second, we validated the mouse Neutrophil Chemotaxis assay by comparing the adhesion and Chemotaxis of Neutrophils from chronically inflamed and wild-type mice; we observed significantly higher Neutrophil adhesion in blood obtained from chronically inflamed mice. Third, we show that 2D and 3D Neutrophil Chemotaxis can be directly compared using our technique. These methods allow for new avenues of research while reducing the complexity, time, and sample volume requirements to perform Neutrophil Chemotaxis assays.

  • the actin regulatory protein hs1 interacts with arp2 3 and mediates efficient Neutrophil Chemotaxis
    Journal of Biological Chemistry, 2012
    Co-Authors: Peter Cavnar, David J Beebe, Erwin Berthier, Kevin Mogen, Anna Huttenlocher
    Abstract:

    HS1 is an actin regulatory protein and cortactin homolog that is expressed in hematopoietic cells. Antigen receptor stimulation induces HS1 phosphorylation, and HS1 is essential for T cell activation. HS1 is also expressed in Neutrophils; however, the function of HS1 in Neutrophils is not known. Here we show that HS1 localizes to the Neutrophil leading edge, and is phosphorylated in response to the chemoattractant formyl-Met-Leu-Phe (fMLP) in adherent cells. Using live imaging in microchannels, we show that depletion of endogenous HS1 in the Neutrophil-like PLB-985 cell line impairs Chemotaxis. We also find that HS1 is necessary for chemoattractant-induced activation of Rac GTPase signaling and Vav1 phosphorylation, suggesting that HS1-mediated Rac activation is necessary for efficient Neutrophil Chemotaxis. We identify specific phosphorylation sites that mediate HS1-dependent Neutrophil motility. Expression of HS1 Y378F, Y397F is sufficient to rescue migration of HS1-deficient Neutrophils, however, a triple phospho-mutant Y222F, Y378F, Y397F did not rescue migration of HS1-deficient Neutrophils. Moreover, HS1 phosphorylation on Y222, Y378, and Y397 regulates its interaction with Arp2/3. Collectively, our findings identify a novel role for HS1 and its phosphorylation during Neutrophil directed migration.

  • Asymmetric localization of calpain 2 during Neutrophil Chemotaxis.
    Molecular biology of the cell, 2006
    Co-Authors: Paul A. Nuzzi, Melissa A. Senetar, Anna Huttenlocher
    Abstract:

    Chemoattractants induce Neutrophil polarization through localized polymerization of F-actin at the leading edge. The suppression of rear and lateral protrusions is required for efficient Chemotaxis and involves the temporal and spatial segregation of signaling molecules. We have previously shown that the intracellular calcium-dependent protease calpain is required for cell migration and is involved in regulating Neutrophil Chemotaxis. Here, we show that primary Neutrophils and Neutrophil-like HL-60 cells express both calpain 1 and calpain 2 and that chemoattractants induce the asymmetric recruitment of calpain 2, but not calpain 1, to the leading edge of polarized Neutrophils and differentiated HL-60 cells. Using time-lapse microscopy, we show that enrichment of calpain 2 at the leading edge occurs during early pseudopod formation and that its localization is sensitive to changes in the chemotactic gradient. We demonstrate that calpain 2 is recruited to lipid rafts and that cholesterol depletion perturbs calpain 2 localization, suggesting that its enrichment at the front requires proper membrane organization. Finally, we show that catalytic activity of calpain is required to limit pseudopod formation in the direction of chemoattractant and for efficient Chemotaxis. Together, our findings identify calpain 2 as a novel component of the frontness signal that promotes polarization during Chemotaxis.

Hidenori Hattori - One of the best experts on this subject based on the ideXlab platform.

  • integrin independent role of caldag gefi in Neutrophil Chemotaxis
    Journal of Leukocyte Biology, 2010
    Co-Authors: Carla Carbo, Daniel Duerschmied, Tobias Goerge, Hidenori Hattori, Jiro Sakai, Stephen M Cifuni, Gilbert C White, Magdalena Chrzanowskawodnicka
    Abstract:

    Chemotaxis and integrin activation are essential processes for Neutrophil transmigration in response to injury. CalDAG-GEFI plays a key role in the activation of beta1, beta2, and beta3 integrins in platelets and Neutrophils by exchanging a GDP for a GTP on Rap1. Here, we explored the role of CalDAG-GEFI and Rap1b in integrin-independent Neutrophil Chemotaxis. In a transwell assay, CalDAG-GEFI-/- Neutrophils had a 46% reduction in transmigration compared with WT in response to a low concentration of LTB4. Visualization of migrating Neutrophils in the presence of 10 mM EDTA revealed that CalDAG-GEFI-/- Neutrophils had abnormal chemotactic behavior compared with WT Neutrophils, including reduced speed and directionality. Interestingly, Rap1b-/- Neutrophils had a similar phenotype in this assay, suggesting that CalDAG-GEFI may be acting through Rap1b. We investigated whether the deficit in integrin-independent Chemotaxis in CalDAG-GEFI-/- Neutrophils could be explained by defective cytoskeleton rearrangement. Indeed, we found that CalDAG-GEFI-/- Neutrophils had reduced formation of F-actin pseudopodia after LTB4 stimulation, suggesting that they have a defect in polarization. Overall, our studies show that CalDAG-GEFI helps regulate Neutrophil Chemotaxis, independent of its established role in integrin activation, through a mechanism that involves actin cytoskeleton and cellular polarization.

  • small molecule screen identifies reactive oxygen species as key regulators of Neutrophil Chemotaxis
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Hidenori Hattori, Jiro Sakai, Kulandayan K Subramanian, Yitang Li, Timothy F Porter, Fabien Loison, Bara Sarraj, Anongnard Kasorn, Hakryul Jo, Catlyn Blanchard
    Abstract:

    Neutrophil Chemotaxis plays an essential role in innate immunity, but the underlying cellular mechanism is still not fully characterized. Here, using a small-molecule functional screening, we identified NADPH oxidase–dependent reactive oxygen species as key regulators of Neutrophil chemotactic migration. Neutrophils with pharmacologically inhibited oxidase, or isolated from chronic granulomatous disease (CGD) patients and mice, formed more frequent multiple pseudopodia and lost their directionality as they migrated up a chemoattractant concentration gradient. Knocking down NADPH oxidase in differentiated Neutrophil-like HL60 cells also led to defective Chemotaxis. Consistent with the in vitro results, adoptively transferred CGD murine Neutrophils showed impaired in vivo recruitment to sites of inflammation. Together, these results present a physiological role for reactive oxygen species in regulating Neutrophil functions and shed light on the pathogenesis of CGD.

  • integrin independent role of caldag gefi in Neutrophil Chemotaxis
    Blood, 2008
    Co-Authors: Carla Carbo, Daniel Duerschmied, Tobias Goerge, Hidenori Hattori, Stephen M Cifuni, Hongbo R Luo, Denisa D Wagner
    Abstract:

    Abstract Neutrophil Chemotaxis and transmigration towards a source of inflammation are two crucial processes for host defense against infection that rely on integrin function. Recently, integrin-independent migration of dendritic cells to the lymph node has been brought to light, although Neutrophil migration in the presence of EDTA was reported many years ago. Ca2+ and diacylglycerol-regulated guanine nucleotide exchange factor I (CalDAG-GEFI), is a small signaling protein that plays a key role in the activation of beta-1, beta-2, and beta-3 integrins in platelets and Neutrophils by activating the small GTPase Rap1. We explored the role of CalDAG-GEFI in integrin-independent Chemotaxis in Neutrophils. Here we report that CalDAG-GEFI−/− Neutrophils have impaired Chemotaxis that is independent of integrin function. In a Chemotaxis transwell assay towards LTB4 and in the presence of 10mM EDTA, CalDAG-GEFI−/− Neutrophils had a 50% reduction in transmigration over 60 minutes compared to wild-type (WT) Neutrophils (p