Fig. 4. Expression of paracellin-1 mutants. (A) Amino acid sequence of the first extracellular loop of paracellin-1. Negatively charged amino acids are labeled in bold and underlined; positively charged amino acids are in bold italics. (B-D) Protein immunoblots of expression of paracellin-1 mutants. (B) Mutations to replace the negatively charged amino acids (D or E) with S or T. Names of mutants are shown underneath the blot, followed by the positions of mutations. (C) Mutations to replace the positively charged amino acids (K or R) with S or T. (D) Mutations found in human patients with FHHNC. (E) Gallery of epifluorescence images showing mis-targeted localization of paracellin-1 mutants in LLC-PK1 cells. D97S, R149T, R149L and S235P in the ER; G239R in the Golgi apparatus. The ER shows a reticular cytoplasmic and perinuclear distribution and the Golgi apparatus tubular structures close to the periphery of the nucleus. Bar, 10 µm.