SEPT5 levels in platelet and brain lysates. (A) Protein concentrations in mouse platelet lysates samples were determined and similar protein amounts were loaded into a reducing 4% to 20% SDS-PAGE. After electrophoresis, the proteins were transferred to nitrocellulose and immunoblotted with an anti-SEPT5 monoclonal antibody (LJ-33). As previously shown, the predominant SEPT5 signal present in platelet lysates is approximately 45 kDa. Quantitation revealed a 2- to 3-fold increase in SEPT5 levels in platelets from GP Ibβ^Null animals. (B) The same membrane was subsequently reacted with an anti-14-3-3ζ polyclonal antibody to document the approximate protein load for each lane using 14-3-3ζ (32 kDa) as an internal standard. (C) Equal quantities of brain lysates protein were analyzed by SDS-PAGE and immunoblotting for the septin protein, SEPT5. (D) The filter shown in panel C was reprobed for 14-3-3ζ protein and is shown for comparison.