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 and immune evasion of the protozoan parasite Leishmania , the causative agent of Leishmaniasis. This study investigates the multifaceted roles of L-CK1.2, which exhibits a dynamic localization pattern and a broad spectrum of interacting partners within the parasite. Using proteomic analysis and confocal microscopy, we identified 230 L-CK1.2-associated proteins (L-CKAPs) across the parasite life stages, promastigotes, which replicate within the insect vector, and amastigotes, which proliferate inside the phagolysosomes of host macrophages. This analysis revealed the ubiquitous presence of L-CK1.2 within various cellular structures, including the cytoskeleton, basal body, and flagellum. Our data also identified 64 host proteins (L-CKAP host ) that interact with L-CK1.2, implicating it in modulating critical host biological processes such as immune response, apoptosis, and purine biosynthesis, processes regulated by Leishmania during infection. The study highlights the dual function of L-CK1.2 as it plays roles both 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 uncovers its importance in regulating intracellular 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.