Synergy between a cytoplasmic vWFA/VIT protein and a WD40-repeat F-box protein controls development in the social amoeba Dictyostelium (Vwa1 IP)

ABSTRACT: Like most eukaryotes, the pre-metazoan social amoeba Dictyostelium depends on the SCF (Skp1/cullin-1/F-box protein) family of E3 ubiquitin ligases to regulate its proteome. In Dictyostelium, starvation induces a transition from unicellular feeding to a multicellular slug that responds to external signals to culminate into a fruiting body containing terminally differentiated stalk and spore cells. These transitions are subject to regulation by F-box proteins and O2-dependent posttranslational modifications of Skp1. Here we examine in greater depth the essential role of FbxW2 and Vwa1, which was found in the FbxWD interactome by co-immunoprecipitation and is classified as a vault protein inter-alpha- trypsin (VIT) and von Willebrand factor-A (vWFA) domain containing protein. Reciprocal co-IPs using gene-tagged strains confirmed the interaction and their similar transcript expression profiles during multicellular development suggest they function together. FbxWD overexpression and proteasome inhibitors did not affect Vwa1 levels suggesting a non-substrate relationship. Forced FbxwD overexpression in slug tip cells where it is normally expressed blocked culmination by a mechanism that depended on its F-box and RING domains, and on Vwa1 expression itself. However, vwa1-disruption alone did not affect development. In contrast, overexpression of either of its three conserved domains arrested development but the effect depended on Vwa1 expression. Based on structure predictions, we propose that the Vwa1 domains exert their negative effect by artificially activating Vwa1 which in turn imbalances its synergistic function with FbxWD. Autoinhibition or homodimerization might be relevant to the poorly understood tumor suppressor role of the evolutionarily related VWA5A/BCSC-1 in humans.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Dictyostelium Discoideum (slime Mold)

SUBMITTER: Christopher West  

LAB HEAD: Christopher Mark West

PROVIDER: PXD035634 | Pride | 2023-10-24

REPOSITORIES: Pride