title: Regulation of hyaluronan binding by F-actin and colocalization of CD44 and phosphorylated ezrin/radixin/moesin (ERM) proteins in myeloid cells.
abstract: Proinflammatory cytokines such as TNF-alpha up-regulate the expression of the cell adhesion molecule, CD44, and induce hyaluronan (HA) binding in peripheral blood monocytes (PBM). Here we show that in PBM, TNF-alpha induced cytoskeletal rearrangement, increased threonine phosphorylation of ERM proteins, and induced the redistribution and colocalization of phospho-ERM proteins (P-ERM) with CD44. In the myeloid progenitor cell line, KG1a, hyaluronan binding occurred in the pseudopod where CD44, P-ERM, and F-actin were highly localized. Hyaluronan binding correlated with high expression of both CD44 and P-ERM clustered in a single pseudopod. Disruption of polymerized actin reduced hyaluronan binding in both PBM and KG1a cells and abolished CD44 clustering and the pseudopod in KG1a cells. The pseudopod was not required for the clustering of CD44, the colocalization with P-ERM, or hyaluronan binding. However, treatment with a kinase inhibitor abolished ERM phosphorylation and reduced hyaluronan binding. Furthermore, expression of CD44 lacking the putative ERM binding site resulted in reduced hyaluronan binding. Taken together, these data suggest that CD44-mediated hyaluronan binding in human myeloid cells is regulated by P-ERM and the actin cytoskeleton.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, #300-6174 University Boulevard, Vancouver, B.C., Canada, V6T 1Z3.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Brown
authors.forename: Darlene
authors.initials: D
authors.lastname: Birkenhead
authors.forename: Jacqueline C Y
authors.initials: JC
authors.lastname: Lai
authors.forename: Liheng
authors.initials: L
authors.lastname: Li
authors.forename: Ruihong
authors.initials: R
authors.lastname: Li
authors.forename: Pauline
authors.initials: P
authors.lastname: Johnson
mesh_terms: D000199:Actins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D022423:Myeloid Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011554:Pseudopodia / Q000276:immunology / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D019311:Staurosporine / Q000494:pharmacology; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000199:Actins; D004268:DNA-Binding Proteins; C086680:ETV5 protein, human; D004791:Enzyme Inhibitors; D018960:Hyaluronan Receptors; D011994:Recombinant Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D006820:Hyaluronic Acid; D004247:DNA; D019311:Staurosporine