Gary R. Carlson, MD, College of Veterinary Medicine

A large-scale analysis of proteins involved in host-cell signalling pathways was performed using chlamydia-infected murine cells in order to identify host proteins that are differentially activated or localized following infection. Two proteins whose distribution was altered in Chlamydia trachomatis-infected cells relative to mock-infected cells were the actin-binding protein adducin and the regulatory kinase Raf-1. Immunoblot analysis with antibodies to both phosphorylated and non-phosphorylated forms of these proteins demonstrated that the abundance of each protein was markedly reduced in the cytosolic fraction of C. trachomatis- and Chlamydophila caviae-infected cells, but the total cellular protein abundance remained unaffected by infection. Fluorescence microscopy of chlamydia-infected cells using anti-alpha-adducin antibodies demonstrated labelling at or near the chlamydial inclusion membrane. Treatment of infected cells with nocodazole or cytochalasin D did not affect alpha-adducin that was localized to the margins of the inclusion. The demonstration of alpha-adducin and Raf-1 redistribution within cells infected by different chlamydiae provides novel opportunities for analysis of host-pathogen interactions in this system.