Journal: bioRxiv
Article Title: MARK3-mediated Slingshot-1 phosphorylation is essential for polarized lamellipodium formation
doi: 10.1101/2023.10.15.562441
Figure Lengend Snippet: (A) MARK3-mediated Ser-937/Ser-978 phosphorylation of SSH1 promotes its binding to 14-3-3. HA-MARK3 was expressed in HEK293T cells, purified using anti-HA immunoprecipitation, and subjected to in vitro kinase reaction using recombinant [Myc+(His) 6 ]-SSH1(WT or 2SA) as a substrate. After centrifugation, supernatants were subjected to in vitro pull-down assay with GST-14-3-3γ bound to glutathione-Sepharose, and the precipitates were analyzed by immunoblotting with anti-Myc and anti-pS-978 antibodies. GST-14-3-3γ was analyzed by CBB staining. The initial supernatants were directly subjected to SDS-PAGE and immunoblotted with anti-Myc and anti-pS-978 antibodies. (B) MARK3 knockdown reduces the interaction between SSH1 and 14-3-3 proteins in cells. HEK293T cells were transfected with the control or MARK3-targeting shRNAs. Endogenous MARK3 expression was analyzed by immunoblotting using an anti-MARK3 antibody. Cell lysates were immunoprecipitated with an anti-SSH1 antibody and the immunoprecipitates were analyzed by immunoblotting with anti-SSH1 and anti-14-3-3 antibodies. Quantitative data are shown as the means ± S.D. of three independent experiments. *, p<0.01. (C) MARK3-mediated Ser-937/Ser-978 phosphorylation and subsequent 14-3-3 binding suppress the cofilin-phosphatase activity of SSH1. [Myc+(His) 6 ]-SSH1(WT or 2SA) was phosphorylated by HA-MARK3 as shown in (B). After centrifugation, the supernatants were incubated with indicated amount of GST-14-3-3γ, and then subjected to in vitro cofilin-phosphatase assay, using P-cofilin as a substrate, in the presence of F-actin. P-cofilin and total cofilin were detected using Pro-Q and CBB staining, respectively.
Article Snippet: P-cofilin and total cofilin were analyzed by Pro-Q Diamond phosphoprotein gel stain kit (Invitrogen) and Coomassie brilliant blue (CBB) staining, respectively.
Techniques: Binding Assay, Purification, Immunoprecipitation, In Vitro, Recombinant, Centrifugation, Pull Down Assay, Western Blot, Staining, SDS Page, Transfection, Expressing, Activity Assay, Incubation, Phosphatase Assay