Localization of γ-tubulin in resting and activated platelets. (A) Purified mouse platelets labeled with anti–γ-tubulin antibody show the localization of microtubule minus ends along the microtubule coil. γ-Tubulin foci averaged 9.06 (± 1.61) signals along the microtubule coil of each platelet (N = 31). (B) Histogram of γ-tubulin signals along the marginal band of mouse platelets. The number of signals ranged from 6 to 12, with a median of 9. (C) Anti–γ-tubulin–stained human platelets show localization at multiple points along the microtubule coil. An average of 9.2 (± 1.7; n = 33) γ-tubulin signals are seen along the coil. (D) Histogram of γ-tubulin signals on the marginal band of human platelets. The number of signals per platelets ranged from 6 to 13, with a median of 9. (E) Western blot detection of γ-tubulin in mouse and human platelet lysates, and HEK 293 cell lysate. Samples of equal protein concentrations were examined. The single protein band detected in each lane shows a relative mobility of approximately 48 kDa, corresponding to the molecular weight of γ-tubulin. (F) Purified human platelets activated with thrombin were formaldehyde-fixed and incubated in anti–γ-tubulin antibody (green) and anti–αβ-tubulin antibody (red). Note the γ-tubulin labeling within the central portion of the activated platelets, while the αβ-tubulin extends outward within filopodia.