Introduction + + 2+ 1 2 1–7 1 5 7 3 8 9 1 3 2 4 7 2 3 2+3 10 15 3 2+3 3 2+3 16 17 18 1 3 16 18 2 18 18 20 19 1 2 3 16 19 20 Fig. 1 2 3 a 3 12 14 b c 2 d 3 Gray areas e 2 3 2+  2 3 3 3 21 2 Materials and methods Materials The sources of antibodies, enzymes or peptide substrates are specified at the appropriate places in the text. Chemicals not otherwise specified were purchased in the highest available quality from Sigma-Aldrich (Taufkirchen, Germany) or Merck (Darmstadt, Germany). 1 2 3 1 2 3 1 2 3 cDNA constructs 1 1 2 2 3 3 22 3 8 2 2 23 Xenopus laevis 22 X. laevis 24 2 2 Heterologous expression in HEK293 cells cDNAs encoding P2X subunits in pcDNA3.1 vector (Invitrogen, Karlsruhe, Germany) or the splicing factor SF3B1 in EGFP-C1 vector were transiently transfected into HEK293 cells using Lipofectamine LTX (Invitrogen, Karlsruhe, Germany). Cells were cultured at 37°C in Dulbecco’s modified Eagle’s medium (DMEM) (Invitrogen) supplemented with 10% (v/v) fetal calf serum (FCS) (PAA Laboratories, Linz, Austria), 100 U/ml of penicillin G and 100 μg/ml of streptomycin. 35 35 L 35 Surface fluorescence labelling of oocytes 2 X. laevis 2+ 3 8 25 4 2 7 2+ Xenopus 4 2 7 g 2 3 In vitro PKC phosphorylation assay 26 32 2 2 In vivo phosphorylation assay 32 SDS-PAGE 14 Immunoblotting 2 3 Two-electrode voltage clamp current recordings and electrical capacitance measurements X. laevis 27 29 2+ 2+ − V 10 mV I cap cap C m Q cap V 30 32 2 X. laevis Data analysis t p Results 2 3 X. laevis 2 1 2 1 18 1 20 1 20 18 19 18 20 2 3 1 2 3 12 14 3 1 1 3 2 2 3 2 3 X. laevis 31 32 + + 2 Fig. 2 2 3 X. laevis a bar m b c black bar 2 b 3 c Gray areas  2 2 3 2 2 3 2 3 2 3 X. laevis 18 20 2 18 19 3 2 2+ 35 3 35 2 3 3 Fig. 3 2 3 2+ 35 X. laevis a 2 3 b 35 c Left panel 2 2 2 2 2 middle panel 35 right panel  3 2 2 2 3 2 3 2 35 3 19 2 2 3 3 2 2 4 2 3 4 4 2 3 X. laevis Fig. 4 2 3 3 a 3 2 23 b 2 3  2 3 1 2 3 2+ X. laevis X. laevis 5 5 32 5 32 1 3 2 1 2 3 1 2 3 5 X. laevis Fig. 5 X. laevis 2 3 2+ X. laevis 32 a b 32 Arrows 1 2 3 Arrowhead X. laevis c 2 3  2 3 2 3 32 6 6 2 3 6 6 Fig. 6 2 3 2 3 X. laevis 32 2+ 42 32 left panel middle panel 32 2 3 right panel  3 32 3 32 32 3 7 3 7 Fig. 7 3 3 32 3 3 arrow 32 3 3 3 bottom panel  Discussion 3 2+3 3 2+3 3 17 33 Evidence for a control of P2X receptor channel function by PKC-mediated phosphorylation 1 2 3 16 19 20 34 5 35 18 20 2 1 3 16 20 34 5 35 1 36 3 16 18 21 2 2 19 37 2 2 2 38 2 2 2 19 1 34 3 3 3 39 40 Evidence against a control of P2X receptor channel function by PKC-mediated phosphorylation 19 2 X. laevis 2 3 1 2 1 19 2 41 2 2 3 21 1 1 1 1 1 18 1 36 1 34 3 16 1 36 1 3 1 3 1 2 4 3