CELL-CYCLE REGULATION OF MAMMARY EPITHELIAL-CELL DETACHMENT BY STAPHYLOCOCCUS-AUREUS

The effect of Staphylococcus aureus on detachment of bovine mammary ep ithelial cells in culture was examined. Mammary epithelial cells becam e detached from fresh monolayers following a 3 h incubation in the pre sence of Staph. aureus M60. Two different procedures indicated that ce ll detachment coincided with the S-Phase of the cell cycle. The roles of proteinases, toxins and Ca availability in inducing cell detachment were examined. Addition of the proteinase inhibitor phenylmethylsulph onyl fluoride (1 mM) to the culture medium prevented cell detachment. Addition of a combination of purified staphylococcal proteinases XVI a nd XVII-B to the culture medium of mammary epithelial cells induced ce ll detachment in the absence of Staph. aureus. Cell detachment may be caused by a staphylococcal proteinase. However, addition of Ca (10 mM) to the culture medium abolished Staph. aureus-induced cell detachment , despite the fact that proteinase activity was still apparently prese nt. Isogenic mutants of Staph. aureus M60, expressing either alpha or beta toxins but not both, induced cell detachment, but to a lesser ext ent than the wild type. Thus, Ca and toxins play some role during cell detachment. Clones established from detached cells that were washed a nd replated showed the same susceptibility to Staph. aureus-induced ce ll detachment as the parental cells. This indicated that there is no s ubclone of mammary epithelial cells more sensitive to this effect.