title: Mycobacterium tuberculosis heparin-binding haemagglutinin adhesin (HBHA) triggers receptor-mediated transcytosis without altering the integrity of tight junctions.
abstract: Mycobacterium tuberculosis, the etiologic agent of tuberculosis, adheres to, invades and multiplies in both professional phagocytes and epithelial cells. Adherence to epithelial cells is predominantly mediated by the 28-kDa heparin-binding haemagglutinin adhesin (HBHA), which is also required for the extrapulmonary dissemination of the bacilli. To study the cellular mechanisms that might result in HBHA-mediated extrapulmonary dissemination, we used a transwell model of cellular barrier and fluorescence microscopy and found that HBHA induces a reorganization of the actin filament network in confluent endothelial cells, but does not affect the tight junctions that link them. When coupled to colloidal gold particles, HBHA-mediated a rapid attachment of the particles to the membrane of human laryngeal epithelial cells (non polarized HEp-2 cells) and human type II pneumocytes (polarized A-549 pneumocytes). After attachment, the particles were internalized in membrane-bound vacuoles that migrated across the polarized pneumocytes to reach the basal side. Attachment of the HBHA-coated particles was not observed when the epithelial cells were pretreated with heparinase III, a lyase that specifically cleaves the heparan sulfate chains borne by the proteoglycans. Furthermore, no binding was observed when the gold particles were coated with HBHA lacking its C-terminal heparin-binding domain. These observations indicate that HBHA induces receptor-mediated endocytosis through the recognition of heparan sulfate-containing proteoglycans by the heparin-binding domain of the adhesin. In addition, the transcellular migration of the endocytic vacuoles containing HBHA-coated particles suggests that HBHA induces epithelial transcytosis, which may represent a macrophage-independent extrapulmonary dissemination mechanism leading to systemic infection by M. tuberculosis.
authors.affiliation: Inserm, U629, Mécanismes Moléculaires de la Pathogénie Microbienne, Institut Pasteur de Lille, 1, rue du professeur Calmette, 59019 Lille cedex, France. franco.menozzi@ibl.fr
authors.forename: Franco D
authors.initials: FD
authors.lastname: Menozzi
authors.forename: Venkata M
authors.initials: VM
authors.lastname: Reddy
authors.forename: Delphine
authors.initials: D
authors.lastname: Cayet
authors.forename: Dominique
authors.initials: D
authors.lastname: Raze
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Debrie
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Dehouck
authors.forename: Roméo
authors.initials: R
authors.lastname: Cecchelli
authors.forename: Camille
authors.initials: C
authors.lastname: Locht
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002417:Cattle; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects*; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D037102:Lectins / Q000494:pharmacology*; D009169:Mycobacterium tuberculosis; D009457:Neuroglia / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects* / Q000502:physiology; D022161:Transport Vesicles / Q000378:metabolism
chemical_list: D000199:Actins; D037102:Lectins; D011509:Proteoglycans; D011956:Receptors, Cell Surface; C104578:heparin-binding hemagglutinin