Research article
Geometric constrains for detecting short actin filaments by cryogenic electron tomography
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* Corresponding authors: Marek Cyrklaff cyrklaff@embl.de - Friedrich Frischknecht fratsch@gmail.com
1 Parasitology, Department of Infectious Diseases, University of Heidelberg Medical School, Im Neuenheimer Feld 324, D-69120 Heidelberg, Germany
2 Center for Cellular Imaging and Nano Analytics (C-CINA), Biocenter, University of Basel, Mattenstrasse 26, CH-4058 Basel, Switzerland
3 Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18, D-82152, Martinsried, Germany
PMC Biophysics 2010, 3:6 doi:10.1186/1757-5036-3-6
Published: 5 March 2010Abstract
Polymerization of actin into filaments can push membranes forming extensions like filopodia or lamellipodia, which are important during processes such as cell motility and phagocytosis. Similarly, small organelles or pathogens can be moved by actin polymerization. Such actin filaments can be arranged in different patterns and are usually hundreds of nanometers in length as revealed by various electron microscopy approaches. Much shorter actin filaments are involved in the motility of apicomplexan parasites. However, these short filaments have to date not been visualized in intact cells. Here, we investigated Plasmodium sporozoites, the motile forms of the malaria parasite that are transmitted by the mosquito, using cryogenic electron tomography. We detected filopodia-like extensions of the plasma membrane and observed filamentous structures in the supra-alveolar space underneath the plasma membrane. However, these filaments could not be unambiguously assigned as actin filaments. In silico simulations of EM data collection and tomographic reconstruction identify the limits in revealing the filaments due to their length, concentration and orientation.
PACS Codes: 87.64.Ee