Abstract
A molecular entity for Ca2+-dependent Cl−-transport has not been well characterized in rat salivary glands. We previously identified a new member of the CLCA family, rCLCA, which we isolated from rat ileum by a PCR-based strategy. Here, we report that rCLCA isoforms are expressed in the submandibular gland (SMG). The full length of rCLCA mRNA is 3.3 kb, and the predicted ORF encodes a 903-a.a. protein. The amino acid sequence of rCLCA protein has 83% homology to murine CLCA1 and 2. Transient transfection of HEK293 cells with rCLCA cDNA resulted in a marked Ca2+-dependent Cl−-conductance with an outward rectification in the I-V relationship. Intense immunostaining was detected in the striated ducts of SMG, but not in the acinar cells. Immunoblot of the membrane fraction of the SMG yielded N-glycosylated 137- and 90-kDa bands. Interestingly, we also found the expression of a truncated isoform (60 kDa, presumably 514 a.a.) including the N-terminal 455 a.a. of the full-length form. Comparison of this mRNA with that of the full-length form revealed that exon 10 is truncated in this isoform. The full-length of rCLCA is likely to be responsible for modulation of Ca2+-dependent Cl− transport in the ductal cells, although the function of the trancated isoform was not defined. [J Physiol Sci. 2006;56 Suppl:S81]
