(A) The GFP-fused Rgd1p F-BAR domain was expressed in wild-type yeast cells (left), cells with a temperature sensitive mutation in Mss4p, the major PtdIns4P 5-kinase (mss4ts; middle), or cells with temperature sensitive mutations in both major PtdIns 4-kinases Stt4p and Pik1p (stt4ts/pik1ts; right). Experiments were performed at (37°C) or below (26°C) the restrictive temperature. PtdIns(4,5)P2 levels are greatly reduced in the mutant strains even at 26°C (Audhya et al., 2000; Stefan et al., 2002). Images are representative of >90% of cells observed, with >100 cells observed in each of at least three independent experiments. (B) Comparison of localization of GFP-fused Rgd1p, Bzz1p, and Hof1p F-BAR domains in HeLa cells (upper panels) and wild-type S. cerevisiae cells (lower panels). Representative cells from >300 analyzed are shown.