Provided herein are four polypeptides, named PRT5, PRT6, PRT7 and PRT8, the nucleic acids encoding the same, compositions comprising the proteins, as well as their uses in therapeutic and diagnostic methods. Antibodies which specifically recognize the polypeptides are also provided, as well as their uses. Characterization of each protein showed that PRT5 and PRT8 are involved in glucose metabolism, PRT6 is involved in androgen regulation, while PRT7 correlates with cancer.