title: Uncovering a role for the tail of the Dictyostelium discoideum SadA protein in cell-substrate adhesion.
abstract: Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA.
authors: Integrated Graduate Program in the Life Sciences, Northwestern University, Chicago, IL 60611, USA.
authors: Anthony S
authors: AS
authors: Kowal
authors: Rex L
authors: RL
authors: Chisholm
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004023:Dictyostelium / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D015800:Protozoan Proteins