pik-iii is a vps34 inhibitor and is able to inhibit autophagy.vps34 kinase has been found to be responsible for synthesis and deposition of phosphatidylinositol-3-phosphate at autophagosome formation sites, resulting in the recruitment of ptdins(3)p-binding proteins.
in previous study, pik-iii was identified as a selective inhibitor of vps34 binding in a hydrophobic pocket. in addition, pik-iii could acutely inhibit the autophagy and lipidation of lc3, which led to the stabilization of autophagy substrates. moreover, substrates such as ncoa4 were identified by conducting ubiquitin-affinity proteomic assay on pik-iii-treated cells, which accumulated in cells with atg7 deficience and co-localized with autolysosomes. ncoa4 could bind ferritin heavy chain-1 directly to target the iron-binding ferritin complex following starvation or iron depletion [1].
animal study showed that pik-iii-treated ncoa4-/- mice had a profound accumulation of iron in splenic macrophages that were important for iron reutilization from engulfed red blood cells. in summary, such in vivo results provided a novel mechanism for selective autophagy of ferritin and revealed a previously untouched role for autophagy and ncoa4 in the control of in-vivo iron homeostasis [1].
[1] dowdle we et al. selective vps34 inhibitor blocks autophagy and uncovers a role for ncoa4 in ferritin degradation and iron homeostasis in vivo. nat cell biol. 2014 nov;16(11):1069-79.
