Proximity labeling reveals cell cycle-specific NEK2 interactions and a regulatory axis controlling NUSAP1 stability

NEK2 is a cell cycle-regulated kinase best known for its role in centrosome separation, yet the phase-specific organization of its interaction network has remained unclear. Here, we combine a doxycycline-inducible TurboID system with mass spectrometry to generate a cell cycle-resolved NEK2 interactome in synchronized U2OS cells. Using generalized additive models (GAMs), we identified different enrichment trajectories of the NEK2 interacting proteins across G1/S, late S, and G2/M, linking NEK2 to chromosome and spindle regulation, RNA-ribonucleoprotein processes, vesicle/lysosome compartments, and ubiquitin-associated pathways. Targeted validations (streptavidin pull-down, co-immunoprecipitation, and immunofluorescence) confirmed the interaction and binding for selected partners. Focusing on NUSAP1, NEK2 induction led to rapid loss of NUSAP1 protein without changes in mRNA levels, and this decrease was blocked by the proteasome inhibitor MG-132. Consistently, NUSAP1 exhibited slower decay in cycloheximide chase assays and reduced ubiquitination in NEK2 knockout cells, indicating NEK2-dependent proteasomal turnover. Global proteomic analysis of NEK2-deficient cells revealed widespread remodeling of protein abundance, including increased NUSAP1 and decreased KIF2C, accompanied by coordinated changes in pathways governing mitotic progression, microtubule organization, and ubiquitin-mediated protein turnover. Together, these findings provide a dynamic map of the NEK2 interactome across the cell cycle and uncover a NEK2-NUSAP1 degradation pathway, offering a framework to study how kinase interactomes are remodeled by cell cycle progression.