## 1 Introduction  
Malaria is a parasitic disease of major public health importance caused mainly by _Plasmodium falciparum_. Its global control is still under serious threat due to the intensive use of the available treatments, participating at least in part of the emergence of multidrug resistance that contributes to a higher risk of transmission, morbidity, and mortality [1]. Consequently, the search for new targets and drugs is imperative. In this context, one strategy is to decipher orthologues of proteins described to play essential roles in other eukaryotes in order to specifically target them in the malaria parasite. Among these proteins, due to the fact of their pleiotropic roles in the dynamic regulation of protein function and cellular distribution, enzymes involved in dephosphorylation processes and, in particular protein phosphatase 1 (PP1), are of interest. PP1 is among the most active drivers of protein dephosphorylation [2]. In humans, there are three PP1 catalytic (PP1c) isoforms expressed by three distinct genes [3]; however, _Plasmodium_ spp. possess only one PP1c. Initial experiments using natural phosphatase inhibitors have shown that okadaic acid was able to drastically inhibit _P. falciparum_ growth in vitro [4; 5]. On the basis of the high IC\({}_{50}\) and IC\({}_{90}\) values observed with okadaic acid in these studies, it was suggested that the significant decrease in growth could mainly be due to PP1. More recently, compelling evidence from genetic studies clearly demonstrated the implication of PP1c not only in the _Plasmodium_ division but also in egress of the blood stage parasites [6]. The PP1 catalytic subunit itself could therefore be considered a promising target for the development of innovative and effective drugs against malaria. However, this could be difficult to achieve, as PP1c is highly conserved in eukaryotes. At the molecular level, it is well known that PP1c forms and functions as a holoenzyme with a vast network of binding partners. Hence, it is reasonable to expect that acting on PP1c interactions or interactors in _Plasmodium_ may lead to the development of selective drugs. In yeast and mammals, PP1c has been shown to function almost exclusively in complexes [7; 8; 9; 10] with diverse regulators/partners to dephosphorylate a plethora of proteins involved in many cellular processes including glycogen metabolism, transcription or mitosis [2]. So far, hundreds of partners have been reported, and many of them have been shown to be involved in the coordination of PP1c activities. These binding partners can be PP1c substrates, recruit additional substrates, transport PP1c, and/or regulate the phosphatase activity. A hallmark of most PP1c regulators is that they exhibit an RVxF sequence as a primary binding motif [7]. At the cellular level, converging studies clearly reported essential functions of some conserved regulators, such as sds22, inhibitors 2 (I2) and 3 (I3), suggesting that the specificity of action of PP1c may originate from the partner rather than from catalytic subunit itself [2]. In _Plasmodium_, we used different approaches combining the study of known conserved regulators, the use of the yeast 2-hybrid approach in which PfPP1c was the bait as well as immunoprecipitated (IP) complexes of blood parasites using HA-tagged PP1c followed by mass spectrometry analyses (MS) to examine the PP1c interactome [11]. This allowed the confirmation of the presence of the conserved sds22 (designated LRR1 in _Plasmodium_) and I2 and I3 partners. Their crucial role was subsequently demonstrated as disrupting their interaction with PfPP1c, induced the death of blood stage parasites [12; 13]. In addition, we reported a high number of specific PP1c _Plasmodium_ partners including GEXP15, whose deletion drastically affected the growth of blood stage parasites and completely blocked the development ofocysts and sporozoites in the mosquito [14].