A recombinant Chlamydia trachomatis major outer membrane protein binds to heparan sulfate receptors on epithelial cells.
Chlamydial attachment to columnar conjunctival or urogenital epithelial cells is an initial and critical step in the pathogenesis of chlamydial mucosal infections. The chlamydial major outer membrane protein (MOMP) has been implicated as a putative chlamydial cytoadhesin; however, direct evidence supporting this hypothesis has not been reported. The function of MOMP as a cytoadhesin was directly investigated by expressing the protein as a fusion with the Escherichia coli maltose binding protein (MBP-MOMP) and studying its interaction with human epithelial cells. The recombinant MBP-MOMP bound specifically to HeLa cells at 4 degrees C but was not internalized after shifting the temperature to 37 degrees C. The MBP-MOMP competitively inhibited the infectivity of viable chlamydiae for epithelial cells, indicating that the MOMP and intact chlamydiae bind the same host receptor. Heparan sulfate markedly reduced binding of the MBP-MOMP to cells, whereas chondroitin sulfate had no effect on binding. Enzymatic treatment of cells with heparitinase but not chondroitinase inhibited the binding of MBP-MOMP. These same treatments were also shown to reduce the infectivity of chlamydiae for epithelial cells. Mutant cell lines defective in heparan sulfate synthesis but not chondroitin sulfate synthesis showed a marked reduction in the binding of MBP-MOMP and were also less susceptible to infection by chlamydiae. Collectively, these findings provide strong evidence that the MOMP functions as a chlamydial cytoadhesin and that heparan sulfate proteoglycans are the host-cell receptors to which the MOMP binds.
Su
H
H
Laboratory of Intracellular Parasites, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, MT 59840, USA.
Raymond
L
L
Rockey
D D
DD
Fischer
E
E
Hackstadt
T
T
Caldwell
H D
HD
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001667:Binding, Competitive; D016466:CHO Cells; D002352:Carrier Proteins / Q000737:chemistry; D002692:Chlamydia trachomatis / Q000472:pathogenicity*; D006224:Cricetinae; D004848:Epithelium / Q000382:microbiology; D029968:Escherichia coli Proteins; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D018272:Porins; D011956:Receptors, Cell Surface / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D013696:Temperature
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D006497:Heparan Sulfate; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D018272:Porins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C461599:maltose transport system, E coli; C071677:omp1 protein, Chlamydia trachomatis