Molecular cloning and characterization of prostase, an androgen-regulated serine protease with prostate-restricted expression

Abstract

The identification of genes with selective expression in specific organs or cell types provides an entry point for understanding biological processes that occur uniquely within a particular tissue. Using a subtraction approach designed to identify genes preferentially expressed in specific tissues, we have identified prostase, a human serine protease with prostate-restricted expression. The prostase cDNA encodes a putative 254-aa polypeptide with a conserved serine protease catalytic triad and an amino-terminal pre-propeptide sequence, indicating a potential secretory function. The genomic sequence comprises five exons and four introns and contains multiple copies of a chromosome 19q-specific minisatellite repeat. Northern analysis indicates that prostase mRNA is expressed in hormonally responsive normal and neoplastic prostate epithelial tissues, but not in prostate stromal constituents. Prostase shares 35% amino acid identity with prostate-specific antigen (PSA) and 78% identity with the porcine enamel matrix serine proteinase 1, an enzyme involved in enamel matrix degradation and with a putative role in the disruption of intercellular junctions. Radiation-hybrid-panel mapping localized prostase to chromosome 19q13, a region containing several other serine proteases, including protease M, pancreatic͞renal kallikrein hK1, and the prostate-specific kallikreins hK2 and hK3 (PSA). The sequence homology between prostase and other well-characterized serine proteases suggests several potential functional roles for the prostase protein that include the degradation of extracellular matrix and the activation of PSA and other proteases.

TheTMPRSS2 gene encoding transmembrane serine protease is overexpressed in a majority of prostate cancer patients: Detection of mutatedTMPRSS2 form in a case of aggressive disease

“…The link between kallikreins and TMPRSS2 is serine protease activity, which is probably involved in malignant processes. For example, prostase (KLK4) is suggested to be associated with prostate cancer, 9 and KLK15, one of the most recently discovered kallikrein genes, is upregulated in this disease. 10 KLK-L4 in turn is downregulated in breast cancer.…”

Identification of exon 1 of prostase/KLK-L1 gene

“…Exon 1, as shown here, is identical to the exon 1 predicted by computer analysis. The rest of the sequence corresponds to the known cDNA sequence of prostase/KLK-L1 (2). Based on the knowledge derived from this study, it is now possible to predict the amino acid sequence of the KLK-L1 protein with confidence.…”

“…Based on the knowledge derived from this study, it is now possible to predict the amino acid sequence of the KLK-L1 protein with confidence. Although the biological function of this protein is not yet known, the high mRNA levels found in the prostate and its upregulation in prostate cancer-derived cell culture in response to androgen (2) suggests that it may play a role in the pathogenesis of androgen-dependent prostatic neoplasia. The localization of the actual exon 1 of this gene allows the determination of the whereabouts of its promoter and aids in the finding of important promoter elements including the verification of putative ARE sequence found for KLK-L1 (4).…”

“…The identification of genes selectively expressed in the human prostate is a key step in furthering these efforts. Prostase/KLK-L1 is one such gene, discovered concurrently by our group using the positional candidate gene approach (1), and by Nelson et al (2), using a subtractive hybridization approach. This novel serine protease is now known to colocalize with PSA and hK2 to chromosome 19q13.3-13.4 (1) and to be upregulated by androgens in the LNCaP cell line (2) and by both androgens and progestins in the breast carcinoma cell line BT-474 (3).…”

“…The similarities between prostase/KLK-L1, PSA, and hK2 suggest that this gene may be a new candidate prostatic biomarker that may also play a role in the pathogenesis of prostatic malignancy. Genomic sequence analysis of this gene (1,2,4) predicted the presence of five exons; however, its PCR amplification from a human prostatic cDNA library (2) and EST libraries (1) could only confirm the presence of exons 2-5. The full characterization of this gene, and its encoded protein, requires knowledge of its first exon.…”