title: CD47 and Nox1 Mediate Dynamic Fluid-Phase Macropinocytosis of Native LDL.
abstract: Macropinocytosis has been implicated in cardiovascular and other disorders, yet physiological factors that initiate fluid-phase internalization and the signaling mechanisms involved remain poorly identified. The present study was designed to examine whether matrix protein thrombospondin-1 (TSP1) stimulates macrophage macropinocytosis and, if so, to investigate the potential signaling mechanism involved.
  
  
  
  TSP1 treatment of human and murine macrophages stimulated membrane ruffle formation and pericellular solute internalization by macropinocytosis. Blockade of TSP1 cognate receptor CD47 and NADPH oxidase 1 (Nox1) signaling, inhibition of phosphoinositide 3-kinase, and transcriptional knockdown of myotubularin-related protein 6 abolished TSP1-induced macropinocytosis. Our results demonstrate that Nox1 signaling leads to dephosphorylation of actin-binding protein cofilin at Ser-3, actin remodeling, and macropinocytotic uptake of unmodified native low-density lipoprotein (nLDL), leading to foam cell formation. Finally, peritoneal chimera studies suggest the role of CD47 in macrophage lipid macropinocytosis in hypercholesterolemic ApoE-/-mice in vivo.
  
  
  
  Activation of a previously unidentified TSP1-CD47 signaling pathway in macrophages stimulates direct receptor-independent internalization of nLDL, leading to significant lipid accumulation and foam cell formation. These findings reveal a new paradigm in which delimited Nox1-mediated redox signaling, independent of classical lipid oxidation, contributes to early propagation of vascular inflammatory disease.
  
  
  
  The findings of the present study demonstrate a new mechanism of solute uptake with implications for a wide array of cell types, including macrophages, dendritic cells, and cancer cells, and multiple pathological conditions in which matrix proteins are upregulated. Antioxid. Redox Signal. 26, 886-901.
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.|3 Vascular Biology Center, Augusta University , Augusta, Georgia .
authors.forename: Gábor
authors.initials: G
authors.lastname: Csányi
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Feck
authors.affiliation: 3 Vascular Biology Center, Augusta University , Augusta, Georgia .
authors.forename: Pushpankur
authors.initials: P
authors.lastname: Ghoshal
authors.affiliation: 3 Vascular Biology Center, Augusta University , Augusta, Georgia .
authors.forename: Bhupesh
authors.initials: B
authors.lastname: Singla
authors.affiliation: 3 Vascular Biology Center, Augusta University , Augusta, Georgia .
authors.forename: Huiping
authors.initials: H
authors.lastname: Lin
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Shanmugam
authors.initials: S
authors.lastname: Nagarajan
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Meijles
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Imad
authors.initials: I
authors.lastname: Al Ghouleh
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Nadiezhda
authors.initials: N
authors.lastname: Cantu-Medellin
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Kelley
authors.affiliation: 4 Jagiellonian Centre for Experimental Therapeutics , Kraków, Poland .
authors.forename: Lukasz
authors.initials: L
authors.lastname: Mateuszuk
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|5 Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Isenberg
authors.affiliation: 6 Center for Biologic Imaging, BSTS, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Simon
authors.initials: S
authors.lastname: Watkins
authors.affiliation: 1 Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.|2 Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Pagano
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D051928:CD47 Antigen / Q000378:metabolism*; D004195:Disease Models, Animal; D006801:Humans; D006937:Hypercholesterolemia / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D000074624:NADPH Oxidase 1 / Q000378:metabolism*; D010766:Phosphorylation; D010873:Pinocytosis; D060066:Protein Interaction Maps; D000067996:RAW 264.7 Cells; D015398:Signal Transduction; D000074084:THP-1 Cells
chemical_list: D051339:Actin Depolymerizing Factors; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051928:CD47 Antigen; C497894:CD47 protein, human; C481348:SPZ1 protein, human; D000074624:NADPH Oxidase 1; C402799:NOX1 protein, human
keywords: CD47; NADPH oxidase; macrophages; macropinocytosis; thrombospondin 1