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ARS Home » Research » Publications at this Location » Publication #105091
Title: ACTIN ENHANCES THE HAEMOLYTIC ACTIVITY OF ESCHERICHIA COLI

Author
item BASARABA, R - KANSAS STATE UNIVERSITY
item BYERLY, A - KANSAS STATE UNIVERSITY
item STEWART, G - KANSAS STATE UNIVERSITY
item MOSIER, D - KANSAS STATE UNIVERSITY
item FENWICK, B - KANSAS STATE UNIVERSITY
item CHENGAPPA, M - KANSAS STATE UNIVERSITY
item LAEGREID, WILLIAM

Submitted to: Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Escherichia coli infections of livestock represent a direct health risk to livestock as well as increasing the potential for contamination of the food supply. Some E. coli produce a toxin, alpha-hemolysin, that enhances their ability to infect animals and helps to produce illness in those animals by lysing or disintegrating animal cells. This study demonstrated that one component released from lysed cells, a protein called actin, actually increases production of an alpha-hemolysin by E. coli. This effect would initiate a cascade by which more hemolysin leads to more lysis and actin release that leads to more hemolysin production and so on. Characterization of this process will indicate the potential for targeted interventions to interfere with hemolysin effects.

Technical Abstract: Actin is a major cytoskeletal protein of mammalian muscle and non-muscle cells. Exposure of cells to soluble factors that damage cell membranes results in the release of actin into the extracellular spaces. The alpha- haemolysin (HlyA) of Escherichia coli is the prototype RTX (repeat in toxin) toxin and is thought to be important in virulence because of its ability to lyse cells by formation of pores in the cell membrane. These studies were conducted to determine if actin influences growth and haemolytic activity of E. coli. Growth of E. coli in the presence of actin resulted in culture supernatant haemolytic activity that was 2.4-, 2.7- and 3.3-fold greater than that of E. coli grown in medium containing BSA, non- supplemented medium, or medium containing heat-denatured actin, respectively. The enhanced haemolytic activity occurred only when actin was present during the growth phase and there was no effect when actin was added to culture supernatants containing haemolysin. The increased haemolytic activity by actin was concentration-dependent, detectable in early-exponential-phase growth, and associated with increased concentrations of secreted HlyA by Western blotting. Actin induced a 2.9- fold increase in alkaline phosphatase activity in E. coli CC118 with a TnphoA insertion in the hlyB determinant of the recombinant haemolysin plamid pWAM04. These results indicate that extracellular actin enhances haemolysin production by E. coli and may have implications in the pathogenesis of E. coli infections.