Coiled Coil Domain Containing Protein 33 (CCDC33)

The CCDC33 protein has been reported to be a cancer/testis (CT) antigen. Mouse Ccdc33 is predominantly expressed in the testis and undergoes alternative splicing to produce at least 4 different transcripts. The protein encoded by Ccdc33 contains 3 coiled-coil domains, a C2-domain, 2 ER membrane retention signal-like motifs and 2 putative peroxisomal targeting signals type 2 (PTS2). Moreover, in HeLa cells CCDC33-dsRED fusion protein co-localized with a known peroxisomal protein, namely PXT1, and showed punctuate intracellular distribution. Taken together, the mouse Ccdc33 encodes a putative peroxisomal protein and is predominantly expressed in male germ cells. The expression starts at the primary spermatocyte stage, suggesting an important role of this protein during spermatogenesis.