Plasmodium falciparum Regulatory Subunit of cAMP-Dependent PKA and Anion Channel Conductance

Abstract

Malaria symptoms occur during Plasmodium falciparum development into red blood cells. During this process, the parasites make substantial modifications to the host cell in order to facilitate nutrient uptake and aid in parasite metabolism. One significant alteration that is required for parasite development is the establishment of an anion channel, as part of the establishment of New Permeation Pathways (NPPs) in the red blood cell plasma membrane, and we have shown previously that one channel can be activated in uninfected cells by exogenous protein kinase A. Here, we present evidence that in P. falciparum-infected red blood cells, a cAMP pathway modulates anion conductance of the erythrocyte membrane. In patch-clamp experiments on infected erythrocytes, addition of recombinant PfPKA-R to the pipette in vitro, or overexpression of PfPKA-R in transgenic parasites lead to down-regulation of anion conductance. Moreover, this overexpressing PfPKA-R strain has a growth defect that can be restored by increasing the levels of intracellular cAMP. Our data demonstrate that the anion channel is indeed regulated by a cAMP-dependent pathway in P. falciparum-infected red blood cells. The discovery of a parasite regulatory pathway responsible for modulating anion channel activity in the membranes of P. falciparum-infected red blood cells represents an important insight into how parasites modify host cell permeation pathways. These findings may also provide an avenue for the development of new intervention strategies targeting this important anion channel and its regulation.

The kinomes of apicomplexan parasites

“…Pharmacological data with the H89 PKA inhibitor, and the inability to produce P. berghei clones lacking a functional PbPKA gene [34], strongly suggest that PKA is essential for Plasmodium schizogony [39] (although it cannot be excluded that the inhibitor has other targets in addition to PKA). cAMP-dependent activity is implicated in the phosphorylation of the cytoplasmic tail of apical membrane antigen 1 (AMA1), a membrane protein essential for erythrocyte invasion [40], and in the regulation of an anion channel in P. falciparuminfected erythrocytes [41].…”

Patch-Clamp Analysis of Membrane Transport in Erythrocytes

“…Several studies have since showed that this channel activity was supported by endogenous channels activated upon infection and that the channels were sensitive to PKA phosphorylation, oxidation or serum presence Bouyer et al, 2011b;Egee et al, 2002;Huber et al, 2005;Huber et al, 2002;Merckx et al, 2008;Staines et al, 2003). Examples of whole-cell currents are given in Figure 6.…”

In silico characterization of Plasmodium falciparum purinergic receptor: a novel chemotherapeutic target

“…Increasing drug resistance in malaria parasite and lack of effective vaccine advocates the need to explore new drugs and vaccine targets to eliminate the disease. Over past few years, there are several reports implicating the role of secondary messengers like calcium, cyclic adenosine monophosphate (cAMP) and their downstream effectors (Merckx et al 2008;Ono et al 2008;Singh et al 2010) at different stages of life cycle of Plasmodium. Recent studies suggested the role of intracellular calcium in the regulation of apical organelles secretion at the time of invasion in P. falciparum (Singh et al 2010).…”