Fig. 4. Endocytosis in fission yeast is associated with actin. (A) Crn1-GFP cells were labelled with FM4-64 examined under the microscope within 1-2 minutes. A subset of endocytic vesicles (red) and Crn1-GFP spots (actin patches, green) are superimposable (yellow). (B) Endocytosis is inhibited Lat B. Crn1-GFP cells were treated with 10 µM Lat B for 10 minutes prior to the addition of FM4-64. Fluorescence remained associated with the cell membrane, particularly at the cell equator, and with some residual structures at the cell membrane. No transfer to internal compartments was observed. (C,D) Effect of drugs on FM4-64 and CDCFDA uptake. Whereas FM4-64 uptake was inhibited by Lat B, CDCFDA uptake was not. TBZ had no effect on the uptake of either probe. (E) In cells preloaded with FM4-64 3 minutes prior to the addition of Lat B or TBZ (arrow) the dye trafficked normally to the vacuole (F). Thus later events of the endocytosis pathway are independent of both actin and microtubules. Bars, 10 µm.