Dynamic association of PfEMP1 and KAHRP in knobs mediates cytoadherence during Plasmodium invasion.

Akshay Kumar Ganguly,Neel Sarovar Bhavesh,Ashutosh Kumar,Priyatosh Ranjan

doi:10.1038/srep08617

Abstract

Plasmodium falciparum infected erythrocytes display membrane knobs that are essential for their adherence to vascular endothelia and for prevention of clearance by the spleen. The knob associated histidine rich protein (KAHRP) is indispensable to knob formation and has been implicated in the recruitment and tethering of P. falciparum erythrocyte membrane protein–1 (PfEMP1) by binding to its cytoplasmic domain termed VARC. However, the precise mechanism of interaction between KAHRP and VARC is not very well understood. Here we report that both the proteins co-localize to membrane knobs of P. falciparum infected erythrocytes and have identified four positively charged linear sequence motifs of high intrinsic mobility on KAHRP that interact electrostatically with VARC in solution to form a fuzzy complex. The current study provides molecular insight into interaction between KAHRP and VARC in solution that takes place at membrane knobs.

Highlights

Plasmodium falciparum infected erythrocytes display membrane knobs that are essential for their adherence to vascular endothelia and for prevention of clearance by the spleen
The current study focuses on the interaction between K2A and VARC in solution and its implications on the mechanism of P. falciparum erythrocyte membrane protein–1 (PfEMP1) tethering to knobs, using a combination of solution-state nuclear magnetic resonance (NMR) spectroscopy, calorimetry and immunofluorescence microscopy
The rationale for truncating K2A is corroborated by the fact that the interaction of K2A with VARC is largely electrostatic in nature[15] and is unlikely to be altered on truncation, given that the theoretical isoelectric pI values of both K2A and K2A1 are identical (9.77) and both possess a net positive charge (116.8 and 19.4, respectively) at pH 7

Summary

Introduction

Plasmodium falciparum infected erythrocytes display membrane knobs that are essential for their adherence to vascular endothelia and for prevention of clearance by the spleen. The knob associated histidine rich protein (KAHRP) is indispensable to knob formation and has been implicated in the recruitment and tethering of P. falciparum erythrocyte membrane protein–1 (PfEMP1) by binding to its cytoplasmic domain termed VARC. We report that both the proteins co-localize to membrane knobs of P. falciparum infected erythrocytes and have identified four positively charged linear sequence motifs of high intrinsic mobility on KAHRP that interact electrostatically with VARC in solution to form a fuzzy complex. The pathogenicity of P. falciparum is, in part, due to its property of avoiding splenic defenses by sequestration of infected erythrocytes in the microvasculature of organs; a phenomenon known as cytoadherence This sequestration causes vascular blockage and is a direct cause of cerebral and placental malaria[2,3]. The current study focuses on the interaction between K2A and VARC in solution and its implications on the mechanism of PfEMP1 tethering to knobs, using a combination of solution-state nuclear magnetic resonance (NMR) spectroscopy, calorimetry and immunofluorescence microscopy

Methods

Results

Conclusion