title: Extracellular Alix regulates integrin-mediated cell adhesions and extracellular matrix assembly.
abstract: Alix (ALG-2-interacting protein X), a cytoplasmic adaptor protein involved in endosomal sorting and actin cytoskeleton assembly, is required for the maintenance of fibroblast morphology. As Alix has sequence similarity to adhesin in Entamoeba histolytica, and we observed that Alix is secreted, we determined whether extracellular Alix affects fibroblast morphology. Here, we demonstrate that secreted Alix is deposited on the substratum of non-immortalized WI38 fibroblasts. Antibody binding to extracellular Alix retards WI38 cell adhesion and spreading on fibronectin and vitronectin. Alix knockdown in WI38 cells reduces spreading and fibronectin assembly, and the effect is partially complemented by coating recombinant Alix on the cell substratum. Immortalized NIH/3T3 fibroblasts deposit less Alix on the substratum and have defects in alpha5beta1-integrin functions. Coating recombinant Alix on the culture substratum for NIH/3T3 cells promotes alpha5beta1-integrin-mediated cell adhesions and fibronectin assembly, and these effects require the aa 605-709 region of Alix. These findings demonstrate that a sub-population of Alix localizes extracellularly and regulates integrin-mediated cell adhesions and fibronectin matrix assembly.
authors.affiliation: Department of Experimental Therapeutics, MD Anderson Cancer Center, The University of Texas, Houston, TX 77030, USA.
authors.forename: Shujuan
authors.initials: S
authors.lastname: Pan
authors.forename: Ruoning
authors.initials: R
authors.lastname: Wang
authors.forename: Xi
authors.initials: X
authors.lastname: Zhou
authors.forename: Joe
authors.initials: J
authors.lastname: Corvera
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Kloc
authors.forename: Richard
authors.initials: R
authors.lastname: Sifers
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gallick
authors.forename: Sue-Hwa
authors.initials: SH
authors.lastname: Lin
authors.forename: Jian
authors.initials: J
authors.lastname: Kuang
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D048430:Cell Shape / Q000502:physiology; D005109:Extracellular Matrix / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism; D039081:Integrin alpha5beta1 / Q000378:metabolism*; D051379:Mice; D011994:Recombinant Proteins / Q000378:metabolism; D019096:Vitronectin / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D005353:Fibronectins; D039081:Integrin alpha5beta1; C492144:Pdcd6ip protein, mouse; D011994:Recombinant Proteins; D019096:Vitronectin