Isoform 1 is strongly expressed in the liver. Isoform 4 is widely expressed, but strongly expressed in all spermatogenesis-related tissues, including the testis, the epithelium of cauda and the corpus epididymis. Isoform 4 is present in the spermatid and mature sperm. Isoform 4 is also expressed in Leydig cells. Isoform 3 is expressed in the testis.
Isoform 4 is phosphorylated by PKA.
Cytoplasm. Mitochondrion. Isoform 4 is found in the mitochondria and localized in the neck of the sperm.