cDNA cloning and expression of a novel human desmocollin

We have cloned a human cDNA encoding for a novel transmembrane protein from a bladder carcinoma cell line (HT-1376) cDNA library. Sequence analysis of this clone revealed an open reading frame of 2,691 bases encoding a protein of 896 amino acids. Sequence comparison showed that this clone has significantly homology to desmocollins, intracellular adhesion molecules belonging to the cadherin superfamily. This protein consists of a signal peptide of 30 amino acids, a precursor segment of 105 amino acids, and a mature protein of 761 amino acids. We expressed this cDNA clone in COS1 cells and found that the predicted cell adhesion molecule remained in the membrane fraction. Antibodies recognizing the predicted mature adhesion molecule of the protein stained antigens along the cell boundaries of both HT-1376 cells and normal human keratinocytes resembling the pattern of desmosome localization. These findings suggest that our clone might be a new member of the desmocollin family, and we have tentatively called this clone human desmocollin type 4.