CATHEPSIN-K - ISOLATION AND CHARACTERIZATION OF THE MURINE CDNA AND GENOMIC SEQUENCE, THE HOMOLOG OF THE HUMAN PYCNODYSOSTOSIS GENE

Cathepsin K(EC 3.4.22.38) is a lysosomal cysteine protease that is str ongly implicated in bone resorption. The human cathepsin It gene is hi ghly expressed in osteoclasts and gene mutations cause pycnodysostosis , an autosomal recessive skeletal dysplasia. To investigate the evolut ionary relatedness of cathepsin K across species, the mouse cathepsin K gene was isolated. A mouse heart cDNA clone, pMCatKl, contained the 3' untranslated region, mature enzyme coding sequence, and most of the propeptide. The remainder of the gene was amplified from mouse melano cyte RNA using 5' rapid amplification of cDNA ends. The gene contained a 990-bp open reading frame, predicting a 329-amino-acid prepropolype ptide. The structure of the protein included a 15-amino-acid presignal , a 99-amino-acid proregion, and a 215-amino-acid mature enzyme. Two p otential N-glycosylation sites were identified, one in the proregion a nd one in the mature enzyme. The 5' untranslated region was 135 bp. Th e 3' untranslated region was 470 bp including a 9-bp poly(A) tract and contained two polyadenylation signals. The mouse cathepsin K nucleoti de and amino acid sequences were highly con served with the human, rab bit, and chicken homologues across the proregion and mature enzyme. Th e mouse cathepsin K gene was isolated from an V129 genomic library, an d characterization of its genomic structure and intron sizes revealed exons with the initiation ATG in exon 2 and termination TGA in exon 8, a genomic organization that was highly conserved with its human homol ogue. The availability of the mouse cathepsin K cDNA and genomic seque nces will facilitate generation of a mouse model of cathepsin K defici ency by gene targeting. (C) 1996 Academic Press, Inc.