Serines 831, 839, 845 and threonines 838 and 840 were mutated to alanine by PCR mutagenesis prior to homologous recombination. A floxed neo cassette was inserted upstream of the last conding exon was removed by cre-mediated recombination following a cross to mice containing Tg(CMV-cre)1Nagy. Western blot analysis with was performed to confirm the presence of the protein but loss of the phosphorylation sites.