Cloning, expression, genomic localization, and enzymatic activities of the mouse homolog of prostate-specific membrane antigen/NAALADase/folate hydrolase

Abstract

Human Prostate Specific Membrane Antigen (PSMA), also known as folate hydrolase I (FOLH1), is a 750-amino acid type II membrane glycoprotein, which is primarily expressed in normal human prostate epithelium and is upregulated in prostate cancer, including metastatic disease. We have cloned and sequenced the mouse homolog of PSMA, which we have termed Folh1, and have found that it is not expressed in the mouse prostate, but primarily in the brain and kidney. We have demonstrated that Folh1, like its human counterpart, is a glutamate-preferring carboxypeptidase, which has at least two enzymatic activities: (1) N-acetylated alpha-linked L-amino dipeptidase (NAALADase), an enzyme involved in regulation of excitatory signaling in the brain, and (2) a gamma-glutamyl carboxypeptidase (folate hydrolase). The 2,256-nt open reading frame of Folh1 encodes for a 752-amino acid protein, with 86% identity and 91% similarity to the human PSMA amino acid sequence. Cells transfected with Folh1 gained both NAALADase and folate hydrolase activities. Examination of tissues for NAALADase activity correlated with the mRNA expression pattern for Folh1. Fluorescent in situ hybridization (FISH) revealed Folh1 maps to only one locus in the mouse genome, Chromosome 7D1-2.

Induction of autoantibodies to syngeneic prostate‐specific membrane antigen by xenogeneic vaccination

“…32 Using this paradigm, we have immunized mice with xenogeneic human PSMA (hPSMA), which shares 85% identity with mouse PSMA (mPSMA) at the amino acid level and has a similar tissue distribution. 33,34 This pattern of expression supports the clinical relevance of a murine model that targets mPSMA.…”

Promoter analysis of human glutamate carboxypeptidase II

“…Human GCP II appears identical to hPSMA and FOLH1 based on cDNA sequence, enzymatic activity and immunoreactivity (Pinto et al, 1996;Luthi-Carter et al, 1998;Halsted et al, 1998;Bacich et al, 2001;Watt et al, 2001). Previous studies reported that 2 Kb and 1.2 Kb of the 5′ promoter of the PSMA gene were effective in driving reporter gene expression in prostate-derived cell lines and non-prostate cell lines but not in CNS-derived cell lines (O'Keefe et al, 1998;Good et al, 1999).…”

“…In the brain, GCP II is primarily, if not exclusively, expressed in astrocytes (Slusher et al, 1992;Berger et al, 1999;Ghose et al, 2004;Sacha et al, 2007). Enzymatic and molecular cloning studies further suggest that GCP II expressed in the human cerebellum, prostate specific membrane antigen (PSMA) expressed on hormone refractory metastatic prostate cancer cells (Israeli et al, 1993), and folate hydrolase I (FOLH1) in the small intestine are identical proteins (Pinto et al, 1996;Luthi-Carter et al, 1998;Halsted, et al,1998;Bacich et al, 2001;Watt et al, 2001). However, their biological functions may significantly differ.…”

Targeting epitopes in prostate-specific membrane antigen for antibody therapy of prostate cancer

“…All the antibodies also reacted with prostate epithelial cells in formalin-fixed prostate tissue (Figure 1). Since mouse and rat kidneys express glutamate carboxypeptidase, 17,18 this tissue was used to test the specificity of 24.4E6 and 14.3C8. Mouse and rat renal cortical tubule cells were stained with 14.3C8, but not with 24.4E6 (photos not shown).…”