Membrane Biophysics of African Trypanosomes

• Applicant: Professor Dr. Markus Engstler, since 5/2021
• Subject Area: Biophysics
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391332795

Sleeping sickness poses a serious threat to humans and livestock in sub-Saharian Africa. It is caused by the trypanosome parasite, a unicellular flagellate and excellent model organism for research in the field ofmembrane biophysics.In the bloodstream of the host the trypanosome plasma membrane is covered with a dense, almost uniform coat of variant surface glycoproteins (VSGs). This highly dynamic surface coat is of vital importance because it protects the parasite from the immune system of the host. Due to its protein density the VSG coat constitutes a promising framework to study macromolecular crowding as well as allows comparative measurements with artificial model membranes. Endo- and exocytosis of diffusing VSG proteins are restricted to the flagellar pocket. This scenario is reminiscent of the so-called narrow escape problem (NEP) in two dimensions. The NEP is a common problem in biology and biophysics. It deals with Brownian particles confined to a given domain with reflecting borders and only a small opening where the particles are absorbed. Applying the currently available analytical solution of the NEP to calculate the time a VSG needs to find the flagellar pocket yields a clear discrepancy with experimental results. We will address the problem in two different ways. First, by measuring VSG dynamics in the external and internal membranes of T. brucei in vivo with single-molecule fluorescence microscopy and looking for non-Brownian components. We aim to identify the influence of physical effects like curvature-assisted sorting in contrast to active cell-dependent contributions. Choosing the well-characterized T. brucei as a model organism allows us to directly test contributions of active players, e.g. molecular motors, in knock-down experiments.Second, by challenging the theory of NE experimentally. In order to test the applicability of the analytical solution, we plan a systematic study in micro-patterned model membranes that allows us to vary geometric parameters and test the validity of the theoretical model in a wide phase space. Moreover, we aim to manipulate the in vivo geometry by knockdown of relevant structural proteins. It is the objective of this project to achieve both a deeper understanding of trypanosome physiology and the fundamental NEP. Ultimately, knowledge of the physical parameters underlying VSG dynamics could be the basis for the development of alternative trypanocide agents that aim to change these parameters and are thus not susceptible to induce resistance.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Dr. Susanne Fenz, until 4/2021