Homology cloning of aspartic proteases from an endocrine cell line using the polymerase chain reaction

Oligonucleotides directed towards the active site regions of aspartic proteases were used as primers for the polymerase chain reaction to identify a unique sequence (asppcr1) from the AtT-20 anterior pituitary corticotrope cell line. Asppcr1 showed the greatest similarity (85% identity) to human cathepsin E [(1989) J. Biol. Chem. 264, 16748-16753]. Northern blot analysis of AtT-20 RNA revealed a single 1.9 kB message. Nuclease protection experiments indicated that asppcr1 mRNA was present in pancreas, spleen, testis and liver at low levels and undetectable in heart and brain. This contrasted with the lysosomal aspartic protease, cathepsin D whose mRNA showed a broader tissue distribution. The restricted message distribution of asppcr1 supports a more specific role for this aspartic protease in aspect(s) of cellular physiology.