Sitkiewicz, E. | bioRxiv Science

bioRxiv2025

Zika virus capsid protein C (ZIKV-C) interactors network mapped by proteomic analysis of human neural stem cells expressing FLAG-tagged C protein.

Zika virus is a teratogenic pathogen belonging to the Flaviviridae family. It possesses the ability to penetrate the placenta and affect the brain development of a fetus, resulting in microcephaly and functional impairments. Mechanisms of this neurotoxicity are still unclear, but capsid proteins of Zika and related viruses are known to exert apoptotic effect in different types of cells, including neurons. To explore the pathways affected by the presence of ZIKV-C, we have performed MS-based interactomic experiment in human neural stem cells and managed to identify 149 putative interactors. Our results indicate that the nucleus (especially the nucleolus) and the mitochondria are the main sites of interaction of protein C with host proteins. A number of the proteins we identified have significant links to diseases of the nervous system, including neurodevelopmental diseases. Furthermore, for the first time, we have identified MAM-domain containing glycosylphosphatidylinositol anchor protein 1, T-complex protein 1 subunit beta, lysine-tRNA ligase, calumenin as particularly abundant ZIKV protein C interactors. Data are available via ProteomeXchange with identifier PXD064412.

molecular biology↗

bioRxiv2025

p70S6 kinase-dependent phosphorylation of the μ2 subunit of the AP2 adaptor complex is needed for clathrin-mediated endocytosis.

Clathrin-mediated endocytosis (CME) internalizes cell-surface receptors via clathrin-coated invaginations of the plasma membrane. Both clathrin and endocytic cargo are recruited to these sites by the adaptor protein complex AP2. AP2 cycles between a closed cytoplasmic conformation and an open membrane-bound state, and efficient CME requires both conformations and their dynamic interconversion. The mechanisms regulating these conformational changes, which include post-translational modifications of the AP2, remain incompletely understood. Here, we report that p70S6 kinase phosphorylates the {micro}2 subunit of the AP2 and that the phosphorylation of serine 45 (S45) depends on p70S6K activity. Loss of S45-{micro}2 phosphorylation results in decreased internalization of canonical CME cargo such as transferrin and PDGF receptors. In Caenorhabditis elegans, lack of S45-{micro}2 phosphorylation produces directionally similar but markedly weaker phenotypes than AP2 loss of function. Live imaging and in silico dynamic modelling suggest that S45-2 phosphorylation has impact on the conformational changes of the AP2 complex. These findings identify a p70S6K-dependent mechanism that modulates AP2 function and further strengthen the importance of post-translational regulation in controlling CME. Summary statementClathrin-mediated endocytosis is essential for receptor internalization and cell signaling. This study identifies a novel regulatory mechanism in which p70S6K-mediated phosphorylation of the AP2 subunit 2 at Ser45 modulates AP2 conformational dynamics and facilitates receptor endocytosis.

cell biology↗