Use of in vivo biotinylated GST fusion proteins to select recombinant antibodies.

Over the last 20 years, continuous advances in the field of molecular biology have led to the development of new strategies to discover and produce monoclonal antibodies, notably by phage display.Here we describe a simple procedure for antibody selection that reduces considerably the undesired selection of non-specific antibodies, based on the use of biotinylated GST proteins fused to a target antigenic sequence. This procedure was tested on a collection of 7 different targets and resulted in the selection of a high percentage (71%) of antibodies specific for each target.

Dictyostelium ACAP-A is an ArfGAP involved in cytokinesis, cell migration and actin cytoskeleton dynamics.

ACAPs and ASAPs are Arf-GTPase-activating proteins with BAR, PH, GAP and ankyrin repeat domains and are known to regulate vesicular traffic and actin cytoskeleton dynamics in mammalian cells. The amoeba Dictyostelium has only two proteins with this domain organization, instead of the six in human, enabling a more precise functional analysis. Genetic invalidation of acapA resulted in multinucleated cells with cytokinesis defects.

Dictyostelium Tom1 participates to an ancestral ESCRT-0 complex.

Sorting of ubiquitinated proteins to multivesicular bodies (MVBs) in mammalian cells relies on proteins with a Vps27/Hrs/STAM (VHS) domain. Here, we show that the amoeba Dictyostelium presents only one protein with a VHS domain: DdTom1. We demonstrate that the VHS domain of DdTom1 is followed by a Golgi-localized, gamma-ear-containing, ADP-ribosylation-factor-binding and Tom1 (GAT) domain that binds ubiquitin, and by a non-conserved C-terminal domain that can recruit clathrin, EGFr pathway substrate 15 and tumor susceptibility gene 101, a component of the MVB biogenesis machinery [endosomal complexes required for transport (ESCRT) complexes].

A Phg2-Adrm1 pathway participates in the nutrient-controlled developmental response in Dictyostelium.

Dictyostelium amoebae grow as single cells but upon starvation they initiate multicellular development. Phg2 was characterized previously as a kinase controlling cellular adhesion and the organization of the actin cytoskeleton. Here we report that Phg2 also plays a role during the transition between growth and multicellular development, as evidenced by the fact that phg2 mutant cells can initiate development even in the presence of nutrients.

Acidic clusters target transmembrane proteins to the contractile vacuole in Dictyostelium cells.

The mechanisms responsible for the targeting of transmembrane integral proteins to the contractile vacuole (CV) network in Dictyostelium discoideum are unknown. Here we show that the transfer of the cytoplasmic domain of a CV-resident protein (Rh50) to a reporter transmembrane protein (CsA) is sufficient to address the chimera (CsA-Rh50) to the CV. We identified two clusters of acidic residues responsible for this targeting, and these motifs interacted with the gamma-adaptin AP-1 subunit in a yeast protein-protein interaction assay.

A novel phosphatidylinositol 4,5-bisphosphate-binding domain targeting the Phg2 kinase to the membrane in Dictyostelium cells.

Phg2 is a ser/thr kinase involved in adhesion, motility, actin cytoskeleton dynamics, and phagocytosis in Dictyostelium cells. In a search for Phg2 domains required for its localization to the plasma membrane, we identified a new domain interacting with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and phosphatidylinositol 4-phosphate (PI(4)P) membrane phosphoinositides. Deletion of this domain prevented membrane recruitment of Phg2 and proper function of the protein in the phagocytic process.