Nucleotide substitutions in exon 2 result in the amino acid substitution of five serines with alanines (p.[Ser351Ala;Ser353Ala;Ser355Ala] and p.(Ser358_Ser359delinsAlaAla)). This prevents phosphorylization of the five residues and the produced protein fails to internalize correctly, but signaling is not disrupted. A loxP site flanked neomycin resistance gene cassette inserted into intron 2 was removed by subsequent cre-mediated recombination.