Dissecting the mechanics of erythrocyte invasion by the malaria parasite P. falciparum

Marion Koch,Baum Laboratory

13/09/2017

(Aikawa, 1971)

The Plasmodium lifecycle

(Cowman et al., 2012)

Host cell invasion by Plasmodium falciparum

(Koch & Baum, 2016)

What do the EBA and Rh proteins actually do during invasion?• EBA175-Glycophorin A: decreased deformability due to increased cross-linking of

receptor to cytoskeleton (Chasis et al., 1988; Karnchanaphanurach et al., 2009)– Locally a point of traction against which motor force can be applied?

• Do parasite host interactions trigger biophysical changes in the red cell that contribute to merozoite invasion?

– Real-Time Deformability Cytometry– Flicker Spectroscopy

(Chasis et al., 1988)

The structural basis of the EBA175-GPA interaction

(Tolia et al., 2005)

Real Time Deformability Cytometry (RT-DC)

(Otto et al., 2015)

Does EBA175 trigger a biophysical change in the RBC?

(Koch et al., 2017)

1. High frame rate video recorded in brightfield

2. Cell contour is traced and extracted over ca. 4,500 frames per cell using a custom-built LabVIEW program

3. Contour data is plotted as displacement of membrane r(θ) at equally spaced points along the cell contour

4. Fourier transformation of this data provides mean square amplitudes h(qx)2 of each mode (q) from which membrane bending modulus (κ) and tension (σ) are calculated using equation:

Kb = Boltzmann constantT = TemperatureA = Area of cellq = mode numberσ = tensionΚ= bending modulus

Adapted from Dasgupta et al., 2014

Tension (σ)Force required to pull membrane

Forces pulling on 2D surface

Bending Modulus (κ)Energy cost due to bending of the membrane

(Koch et al., 2017)

(Koch et al., 2017)

(Tolia et al., 2005)

Does EBA175 binding to its receptor GPA initiate cytoskeletal or membrane changes?

(Koch et al., 2017)

Do EBA175 triggered RBC tension and bending modulus changes affect malaria parasite invasion efficiency?

Model & Conclusions

• EBA175 binding to its RBC receptor GPA triggers tension and bending modulus changes, the latter of which reduces the energy requirement to bend the RBC membrane

• Decreasing the bending modulus increases invasion efficiency

(Koch et al., 2017)

What next?• Does higher cholesterol RBC content affect P. falciparum invasion efficiency?

• How does this relate to obesity and hypercholesterolemia?

Acknowledgements• All members of the Baum lab

– Kate Wright– Oliver Lyth– Fernando Sanchez-Roman Teran– Mark Wilkinson– Charlie Saunders– Michael Delves– Ursula Straschil– Jake Baum

• Flicker Spectroscopy (Dept Chemistry, Imperial College London)

– Nick Brooks

• Real Time Deformability Cytometry (Biotechnology center, Technische Universitaet Dresden, Germany)

– Maik Herbig– Oliver Otto– Jochen Guck

• EBA175– Niraj Tolia– Nicola Salinas

• Miltenverger V Cells– Tim Satchwell