Updated project metadata. Variants in NBEAL2 are causal of Grey Platelet Syndrome (GPS), a rare bleeding disorder characterized by absence of alpha- and specific- granules in platelets and neutrophils, respectively. The role of the scaffolding multidomain NBEAL2 protein in cell biology and granule homeostasis is unknown. We have performed proteomics to identify NBEAL2’s binding partners followed by different layers of validation including biochemical, cellular and functional analysis in vitro and in vivo.