Fig. 5. PI 3-kinase activity is involved in Rickettsia conorii uptake. (A) A specific inhibitor of PI 3-kinase activity (wortmannin) blocks R. conorii invasion, with 64% inhibition at 200 nM compared to levels in control cells. (B) R. conorii infection of Vero cells leads to co-immunoprecipitation of p85 with tyrosine phosphoproteins within minutes of infection (arrow), suggesting that PI 3-kinase activation is an important event in the entry process. Densitometric analysis of scanned blots indicates the relative amount of p85 that co-immunoprecipitates with pTyr proteins during R. conorii infection. Immunoblot analysis of cellular lysates with anti-p85 antibodies.