Plasmodium PKG interacts with ICM1, a multi-pass membrane protein, in both asexual and sexual stages

In malaria parasites, all cGMP-dependent signalling is mediated through a single cGMP-dependent protein kinase (PKG). A major function of PKG is to control calcium signals essential for the parasite to exit red blood cells or for transmission to the mosquito vector. However, how PKG controls these signals in the absence of known second messenger-dependent calcium channels or scaffolding proteins remains a mystery. Here we identify a tightly-associated PKG partner protein in Plasmodium falciparum asexual blood stages. Named ICM1, the partner is a polytopic membrane protein with homology to transporters and calcium channels, raising the possibility of a direct functional link between PKG and calcium homeostasis