SepZ/EspZ is secreted and translocated into HeLa cells by the enteropathogenic Escherichia coli type III secretion system.
Enteropathogenic Escherichia coli (EPEC) is a major bacterial cause of infantile diarrhea in developing countries and is the prototype for a group of gastrointestinal pathogens causing characteristic attaching and effacing (A/E) histopathology on intestinal epithelia. A/E pathogens utilize a type III secretion system (TTSS), encoded by the locus of enterocyte effacement (LEE) pathogenicity island, to deliver effector proteins into host cells. Here, we investigate sequence divergence of the LEE-encoded SepZ protein and identify it as a TTSS-secreted and -translocated molecule. SepZ is hypervariable among A/E pathogens, with sequences sharing between 60 to 81% amino acid identity with SepZ of EPEC. A SepZ-CyaA fusion was secreted and translocated into HeLa cells in a TTSS-dependent manner. Additionally, we determined that the first 20 amino acids of SepZ were sufficient to direct its translocation. In contrast to previous studies suggesting a role in invasion and the structure and/or regulation of the TTSS, we found that SepZ does not mediate uptake of EPEC into host cells or affect translocation and tyrosine phosphorylation of the translocated intimin receptor. Immunohistochemistry reveals that, after an extended HeLa cell infection, accumulated SepZ can be detected beneath the site of bacterial attachment in a subset of pedestal regions. To indicate its newly identified status as a translocated effector protein, we propose to rename SepZ as EspZ.
Kanack
Kristen J
KJ
Center for Vaccine Development and Deparmtent of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., Baltimore, Maryland 21201, USA.
Crawford
J Adam
JA
Tatsuno
Ichiro
I
Karmali
Mohamed A
MA
Kaper
James B
JB
D037361:Adenylate Cyclase Toxin / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D004926:Escherichia coli / Q000378:metabolism / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D005839:Gentamicins / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism
D037361:Adenylate Cyclase Toxin; D029968:Escherichia coli Proteins; D005839:Gentamicins; D011956:Receptors, Cell Surface; C103307:SepZ protein, E coli; C109287:Tir protein, E coli