Cytoskeleton and Rho GTPases as targets of Streptococcus pneumoniae pneumolysin in meningitis and CNS dysfunction

• Applicant: Asparouh Iliev, Ph.D.
• Subject Area: Pharmacology
• Term: from 2007 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 50622976

Streptococcus pneumoniae is a common pathogen causing the most frequent form of bacterial meningitis in adults and the second most common form in children, leading to death in 30% of the cases and neurological sequelae in more than 30% of the survivors. A major virulence factor of S. pneumoniae is the pore-forming toxin pneumolysin. It belongs to the family of cholesterol-dependent cytolysins, including perfringolysin, streptolysin and others. It induces rapid cell lysis or apoptosis in a concentration-dependent manner. The serious outcome and prognosis of pneumococcal meningitis contrast with the limited presence of cell death. Recently, a cholesterol-dependent rapid activation of RhoA and Rac1 GTPases by pneumolysin and subsequent actin cytoskeletal remodeling in neuronal cells has been described. The aim of the project is to clarify the molecular steps leading to the small GTPase activation, to redistribution of the cytoskeleton and to changes in cell signaling of neuronal target cells after pneumolysin challenge. Various toxin mutants (e.g. non-pore forming) will be employed to analyze the role of macropores/micropore formation in GTPase activation and to identify critical toxin domains. The traffic and recruitment of small GTPases and their regulators (GEFs and GAPs) to the cell membrane cholesterol-rich microdomains and/or membrane/cytosol redistribution will be analyzed. Finally, alterations of dendritic spine (precursors of mature synapses) formation (depending on small GTPases) under the effect of the toxin will be examined. These effects will be compared with other pore-forming toxins.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Fluorescent microscope with incubator and imaging system
• Instrumentation Group: 5170 Elektronenoptische Bildwandlergeräte und Bildverstärker (außer Fernsehanlagen 673)