To the time period and the number of washing cycles (cf. Fig. S1). The second set of plates was used as control to normalize the specifically bound radioactivity to the protein content. For this purpose, the cells of the control wells were lysed with a buffer (50?100 mL, volume dependent on the protein concentration), consisting of 25 mM Tricine (pH 7.8), 10 glycerol, 1 TritonTM X-100 (Serva) and 1 mM dithiothreitol (Sigma), for 30 min under shaking. 5 mL of each lysate were analyzed by the Bradford protein assay after appropriate dilution.Cy5-pNPY (100 mL of a two-fold concentrated solution in L15 medium) for total binding as well as with the competing agent (100 mL of a two-fold concentrated solution in 23727046 L15 medium) and Cy5-pNPY (100 mL of a two-fold concentrated solution in L15 medium) for displacement. Images were acquired after an incubation period of 7? min (excitation at 633 nm (10 laser transmission), 650 nm long-pass filter). Visualization of Y1Rs using the fluorescent Y1R-JW 74 web selective ligand UR-MK22 was performed as reported [27] with the following variations: on the day of the experiment confluence of the cells was about 70?0 . Images were acquired after an incubation period of 16 min (excitation at 488 nm (5.1 laser transmission), 560 nm long-pass filter).Calcium AssayThe intracellular Ca2+ concentration in MCF-7 (L) cells was measured by a spectrofluorimetric assay with the fluorescent Ca2+ indicator fura-2. The assay was performed by analogy with a protocol established for HEL cells in our laboratory [28]. Prior to the assay, MCF-7 cells were incubated with 1 nM 17b-estradiol alone or in combination with 100 nM fulvestrant, or the respective vehicle, for 45 h. Calcium mobilization in MCF-7 cells was stimulated by 10 nM pNPY. To antagonize the Y1R mediated calcium mobilization, BIBP3226 (100 nM) was added 1 min prior to the addition of pNPY. The ratio R of fluorescence intensities at 510 nm after excitation at 340 and 380 nm was used for the calculation of the calcium concentration according to the Grynkiewicz equation [29]: [Ca2+] = KD ? (R – Rmin)/(Rmax – R)Confocal MicroscopyImages were acquired with a Zeiss Axiovert 200 M microscope equipped with the LSM 510 laser scanner. Two days before the experiment MCF-7 (L) cells were trypsinized and seeded in ibiTreat m-slide 8-well cover glasses (Ibidi, Planegg, Germany) in EMEM containing 1 nM 17-b-estradiol and 5 FCS. At a confluence of the cells of about 80 the culture medium was removed, the cells were washed with Leibowitz L15 culture medium (200 mL) and covered with L15 medium (100 mL) andNPY Y1 Receptor Down-Regulation by AntiestrogensFigure 4. NPY Y1R expression in MCF-7 cells. Detection of NPY receptor subtype(s) expressed by MCF-7 (L) cells (216th (A ) and 172th (E,F) Docosahexaenoyl ethanolamide cost passage) using confocal microscopy. A (rainbow): Cells were incubated with the fluorescent Y1, Y2 and Y5 receptor agonist Cy5-pNPY (10 nM) alone (A) or in combination with selective antagonists (Y1R: BIBP3226 (B), Y2R: BIIE0246 (C), Y5R: CPG71683 (D)) at a concentration of 1 mM each (100-fold excess to Cy5-pNPY). Cy5-pNPY was displaced by the Y1R selective antagonist only (B). E,F (glow scale): Binding of the Y1R selective fluorescent antagonist UR-MK22 (60 nM) to Y1Rs in the cell membrane. E: total binding, F: unspecific binding in the presence of BIBP3226 (100-fold excess). doi:10.1371/journal.pone.0051032.g? SFB (KD: dissociation constant of the fura-2-Ca2+ complex = 224 nM; Rmax: fluorescence ratio.To the time period and the number of washing cycles (cf. Fig. S1). The second set of plates was used as control to normalize the specifically bound radioactivity to the protein content. For this purpose, the cells of the control wells were lysed with a buffer (50?100 mL, volume dependent on the protein concentration), consisting of 25 mM Tricine (pH 7.8), 10 glycerol, 1 TritonTM X-100 (Serva) and 1 mM dithiothreitol (Sigma), for 30 min under shaking. 5 mL of each lysate were analyzed by the Bradford protein assay after appropriate dilution.Cy5-pNPY (100 mL of a two-fold concentrated solution in L15 medium) for total binding as well as with the competing agent (100 mL of a two-fold concentrated solution in 23727046 L15 medium) and Cy5-pNPY (100 mL of a two-fold concentrated solution in L15 medium) for displacement. Images were acquired after an incubation period of 7? min (excitation at 633 nm (10 laser transmission), 650 nm long-pass filter). Visualization of Y1Rs using the fluorescent Y1R-selective ligand UR-MK22 was performed as reported [27] with the following variations: on the day of the experiment confluence of the cells was about 70?0 . Images were acquired after an incubation period of 16 min (excitation at 488 nm (5.1 laser transmission), 560 nm long-pass filter).Calcium AssayThe intracellular Ca2+ concentration in MCF-7 (L) cells was measured by a spectrofluorimetric assay with the fluorescent Ca2+ indicator fura-2. The assay was performed by analogy with a protocol established for HEL cells in our laboratory [28]. Prior to the assay, MCF-7 cells were incubated with 1 nM 17b-estradiol alone or in combination with 100 nM fulvestrant, or the respective vehicle, for 45 h. Calcium mobilization in MCF-7 cells was stimulated by 10 nM pNPY. To antagonize the Y1R mediated calcium mobilization, BIBP3226 (100 nM) was added 1 min prior to the addition of pNPY. The ratio R of fluorescence intensities at 510 nm after excitation at 340 and 380 nm was used for the calculation of the calcium concentration according to the Grynkiewicz equation [29]: [Ca2+] = KD ? (R – Rmin)/(Rmax – R)Confocal MicroscopyImages were acquired with a Zeiss Axiovert 200 M microscope equipped with the LSM 510 laser scanner. Two days before the experiment MCF-7 (L) cells were trypsinized and seeded in ibiTreat m-slide 8-well cover glasses (Ibidi, Planegg, Germany) in EMEM containing 1 nM 17-b-estradiol and 5 FCS. At a confluence of the cells of about 80 the culture medium was removed, the cells were washed with Leibowitz L15 culture medium (200 mL) and covered with L15 medium (100 mL) andNPY Y1 Receptor Down-Regulation by AntiestrogensFigure 4. NPY Y1R expression in MCF-7 cells. Detection of NPY receptor subtype(s) expressed by MCF-7 (L) cells (216th (A ) and 172th (E,F) passage) using confocal microscopy. A (rainbow): Cells were incubated with the fluorescent Y1, Y2 and Y5 receptor agonist Cy5-pNPY (10 nM) alone (A) or in combination with selective antagonists (Y1R: BIBP3226 (B), Y2R: BIIE0246 (C), Y5R: CPG71683 (D)) at a concentration of 1 mM each (100-fold excess to Cy5-pNPY). Cy5-pNPY was displaced by the Y1R selective antagonist only (B). E,F (glow scale): Binding of the Y1R selective fluorescent antagonist UR-MK22 (60 nM) to Y1Rs in the cell membrane. E: total binding, F: unspecific binding in the presence of BIBP3226 (100-fold excess). doi:10.1371/journal.pone.0051032.g? SFB (KD: dissociation constant of the fura-2-Ca2+ complex = 224 nM; Rmax: fluorescence ratio.
