Proline rich acidic protein and uses thereof

#The present invention relates to proline-rich acidic protein (PRAP) and PRAP isoforms and polynucleotides which identify and encode them. In addition, the invention provides expression vectors and host cells, agonists, antibodies. In particular, the invention provides methods for preventing or treating disorders associated with the expression of PRAP.

#The Proline-rich acidic protein (PRAP) gene was first identified in the mouse as a pregnant-specific uterine protein (psup) (Kasik and Rice, 1997). The gene was expressed in the mouse uterus from day 12 of pregnancy to the third day after parturition. Studies conducted in the laboratory demonstrated that PRAP expression was not limited to the late pregnant uterus (Zhang et al., 2000). PRAP mRNA was found abundantly expressed in the proximal small intestine of both the rat and mouse. Expression was highest in the proximal small intestine. Expression decreased distally and was undetectable in the terminal ileum in Northern blots.

#The PRAP gene encodes a novel protein expressed at high concentrations in human kidney, liver and the gastrointestinal tract. It has no homology to known proteins. However, the presence of a signal peptide in the N-terminal part of the protein suggests that it is a secreted protein.

#FIG. 1: Nucleotide and predicted amino acid sequence of PRAP. The cDNA sequence and predicted open reading frame (single letter codes) are shown. Gene-specific primers used in the 5′- and 3′-RACE are indicated by arrows: forward primers prapF1 and prapF2, and reverse primers prapR1 and prapR2. The respective translation initiation and termination sites are indicated in bold. The primers used for the amplification of the probe for Northern hybridisations (F0 and R0) and real-time RT-PCR (F3 and R3) are indicated by arrows. The conserved GenBank expressed sequence tag sequence is shaded. Potential casein kinase II phosphorylation sites are boxed.

#FIG. 2: Northern blot analysis of PRAP gene expression in human tissues. The human 12-lane MTN blot preloaded with 2 μg of purified polyadenylated RNA from different tissues was hybridised with PRAP probe. Lane 1: brain, Lane 2: heart, Lane 3: skeletal muscle, Lane 4: colon, Lane 5: thymus, Lane 6: spleen, Lane 7: kidney, Lane 8: liver, Lane 9: small intestine, Lane 10: placenta, Lane 11: lung, Lane 12: peripheral blood lymphocyte.

#FIG. 3: Expression of PRAP in gastrointestinal tract (GI). Summary of Northern blot data showing PRAP expression in normal mucosa of GI. The number of samples in each group (from stomach) is indicated above the bars. The relative densitometric units shown were expressed against 18S to correct for minor loading differences.

#SEQ ID NO:1 is the gene sequence of the PRAP protein.

#SEQ ID NO:2 is the amino acid sequence of PRAP protein.

#SEQ ID NO:3 is the amino acid sequence of a novel isoform of the PRAP protein.