Characterization of the dual functions of Leishmania CK1.2 in both the parasite and the macrophage using integrated proteomics and spatial mapping

Leishmania CK1.2 (L-CK1.2) is a serine/threonine protein kinase essential for the survival of the protozoan parasite Leishmania , the causative agent of Leishmaniasis. This study investigates the dynamic localization pattern of L-CK1.2 and the broad spectrum of its interacting partners within the parasite. Using proteomic analysis and confocal microscopy, we identified 230 L-CK1.2-associated proteins across the parasite life stages, promastigotes (in the insect vector), and amastigotes, (in the phagolysosomes of host macrophages). This analysis revealed the ubiquitous presence of L-CK1.2 in various cellular structures, including the cytoskeleton, basal body, and flagellum. Using an in vitro system, sixty-four host L-CK1.2-associated proteins, involved in critical host biological processes such as immune response, apoptosis, and purine biosynthesis, were shown to interact with L-CK1.2. These processes are known to be regulated by Leishmania during infection. The study highlights the dual function of L-CK1.2, in the parasite (cis) and within the host cell (trans), positioning this kinase as a key player in host-pathogen interactions. This work provides a comprehensive map of L-CK1.2 interactions and suggest its potential importance in regulating intracellular Leishmania survival, providing potential therapeutic targets for Leishmaniasis. Furthermore, given the evolutionary conservation of CK1.2 across other parasitic organisms, our findings may have broader implications for understanding and managing parasitic infections.