title: The mammalian actin-binding protein 1 is critical for spreading and intraluminal crawling of neutrophils under flow conditions.
abstract: Recently, the mammalian actin-binding protein 1 (mAbp1; Hip-55, SH3P7, debrin-like protein) was identified as a novel component of the β(2) integrin-mediated signaling cascade during complement-mediated phagocytosis and firm adhesion of polymorphonuclear neutrophils (PMN) under physiological shear stress conditions. In this study, we found that the genetic ablation of mAbp1 severely compromised not only the induction of adhesion, but also subsequent spreading of leukocytes to the endothelium as assessed by intravital microscopy of inflamed vessels of the cremaster muscle of mice. In vitro studies using murine PMN confirmed that mAbp1 was required for β(2) integrin-mediated spreading under shear stress conditions, whereas mAbp1 was dispensable for spreading under static conditions. Upon β(2) integrin-mediated adhesion and chemotactic migration of human neutrophil-like differentiated HL-60 cells, mAbp1 was enriched at the leading edge of the polarized cell. Total internal reflection fluorescence microscopy revealed that mAbp1 formed propagating waves toward the front of the lamellipodium, which are characteristic for dynamic reorganization of the cytoskeleton. Accordingly, binding of mAbp1 to actin was increased upon β(2) integrin-mediated adhesion, as shown by coimmunoprecipitation experiments. However, chemotactic migration under static conditions was unaffected in the absence of mAbp1. In contrast, the downregulation of mAbp1 by RNA interference technique in neutrophil-like differentiated HL-60 cells or the genetic ablation of mAbp1 in leukocytes led to defective migration under flow conditions in vitro and in inflamed cremaster muscle venules in the situation in vivo. In conclusion, mAbp1 is of fundamental importance for spreading and migration under shear stress conditions, which are critical prerequisites for efficient PMN extravasation during inflammation.
authors.affiliation: Walter Brendel Centre of Experimental Medicine, Ludwig Maximilians University Munich, 80336 Munich, Germany.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Hepper
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schymeinsky
authors.forename: Ludwig T
authors.initials: LT
authors.lastname: Weckbach
authors.forename: Sascha M
authors.initials: SM
authors.lastname: Jakob
authors.forename: David
authors.initials: D
authors.lastname: Frommhold
authors.forename: Michael
authors.initials: M
authors.lastname: Sixt
authors.forename: Melanie
authors.initials: M
authors.lastname: Laschinger
authors.forename: Markus
authors.initials: M
authors.lastname: Sperandio
authors.forename: Barbara
authors.initials: B
authors.lastname: Walzog
mesh_terms: D000818:Animals; D018821:CD18 Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002465:Cell Movement / Q000235:genetics / Q000276:immunology*; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology; D004730:Endothelium, Vascular / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D018922:HL-60 Cells; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D011554:Pseudopodia / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D033081:Shear Strength; D018909:src Homology Domains / Q000235:genetics / Q000276:immunology*
chemical_list: D018821:CD18 Antigens; C117063:DBNL protein, human; C485512:Dbnl protein, mouse; D008840:Microfilament Proteins