INTERNALIZATION OF ESCHERICHIA-COLI BY HUMAN RENAL EPITHELIAL-CELLS IS ASSOCIATED WITH TYROSINE PHOSPHORYLATION OF SPECIFIC HOST-CELL PROTEINS

Human renal epithelial cells are capable of internalizing Escherichia coli regardless of whether the bacteria are isolated from individuals with pyelonephritis or from healthy volunteers. In this study, we inve stigated the role of bust cell tyrosine kinase activity in internaliza tion, We found that internalization of both fecal and pyelonephritis i solates is blocked by tyrosine kinase inhibitors. We found increased i ntensity of two tyrosine-phosphorylated proteins, with relative mobili ties of approximately 123,000 and 110,000, in Western blots of extract s from human renal epithelial cells infected with E. coli. The increas ed intensity of these tyrosine-phosphorylated proteins was observed on ly in the Triton X-100-insoluble fraction, suggesting that these prote ins could be associated with the cytoskeleton. Increased tyrosine phos phorylation of these proteins upon E. coli infection was observed in b oth transformed and primary human renal epithelial cells and in cells infected with several different strains of E. coli isolated from the f eces of healthy individuals or from the blood or urine of patients wit h pyelonephritis. The increased tyrosine phosphorylation of these prot eins required live bacteria and was blocked by tyrosine kinase inhibit ion but not by protein synthesis inhibitors or cytochalasin D. These e xperiments establish a strong link, between E. coli internalization an d host cell signaling through tyrosine kinases in human kidney cells a nd provide evidence that specific proteins are involved in these proce sses.