Fig. 7. Treatment of retina cells with SFRP1 is associated with phospho-Ser⁹-mediated inhibition of GSK3ß activity. (A) SFRP1-inhibits GSK3ß activity by phosphorylation at Ser⁹. SFRP1- or control-treated retina cells, harvested three or five hours after the culture, were analysed by immunoblots with antibodies -GSK3ß-phospho-Ser⁹ (inactive form), GSK3ß-phospho-Tyr²¹⁶ (active form) and -tubulin, as loading control. NDV indicate a clear increase in phospho-Ser⁹-mediated inhibition of GSK3ß activity. (B) The total and phospho-Ser⁹-fraction of GSK3ß was evaluated with specific antibodies by western blots in retina explants electroporated with either Gfp or Sfrp1-myc and collected five hours after protein expression. Total content of GSK3ß was normalised against -tubulin. Phospho-Ser⁹ positive bands were normalised against total GSK3ß content. Anti-myc demonstrates Sfrp1-myc expression after electroporation.