Identification of Host Proteins Involved in Rickettsial Invasion of Tick Cells

Abstract

Tick-borne spotted fever group (SFG)Rickettsiaspecies are obligate intracellular bacteria capable of infecting both vertebrate and invertebrate host cells, an essential process for subsequent bacterial survival in distinct hosts. The host cell signaling molecules involved in the uptake ofRickettsiainto mammalian andDrosophilacells have been identified; however, invasion into tick cells is understudied. Considering the movement of SFGRickettsiabetween vertebrate and invertebrate hosts, the hypothesis is that conserved mechanisms are utilized for host cell invasion. The current study employed biochemical inhibition assays to determine the tick proteins involved inRickettsia montanensisinfection of tick-derived cells from a natural host,Dermacentor variabilis. The results revealed several tick proteins important for rickettsial invasion, including actin filaments, actin-related protein 2/3 complex, phosphatidylinositol-3′-kinase, protein tyrosine kinases (PTKs), Src family PTK, focal adhesion kinase, Rho GTPase Rac1, and neural Wiskott-Aldrich syndrome protein. Delineating the molecular mechanisms of rickettsial infection is critical to a thorough understanding of rickettsial transmission in tick populations and the ecology of tick-borne rickettsial diseases.