Functional characterization of L1156F CFTR: a newly identified mutation in Japanese patients with chronic pancreatitis

Abstract

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated chloride channel that plays an important role in bicarbonate transport in the exocrine pancreas. Accumulating evidence suggests that CFTR mutations are associated with a subset of patients with chronic pancreatitis. We have identified a new point mutation (L1156F) in exon 18 in patients with chronic pancreatitis. In order to elucidate a disease associated with this mutation, we examined the function of L1156F-CFTR. The mutation was introduced in pCMV-wild type (WT) CFTR plasmid by site directed mutagenesis. Chloride channel activity was measured in HEK293 cells expressing either WT or L1156F-CFTR by whole cell current recording. The amount of CFTR proteins expressed was analyzed by immuno-blotting using an anti-CFTR antibody. When stimulated with 10μM forskolin, WT and L1156F generated a chloride current of 1534±72 and 476±45 pA (n=5), respectively. The introduction of the L1156F mutation did not affect the expression of CFTR protein compared with the WT. In conclusion the L1156F mutation reduces the CFTR chloride current by 69%. The lack of lung and intestinal symptoms and the chronic pancreatitis in these patients further highlight that low activity of CFTR is sufficient for normal lung and intestinal function and the particular susceptibility of the pancreas to mutations in CFTR. [J Physiol Sci. 2006;56 Suppl:S71]