Phosphorylation of mouse sperm axoneme central apparatus protein SPAG16L by a testis-specific kinase, TSSK2.

The mammalian protein the ortholog of Chlamydomonas Pf20, is an axoneme central apparatus protein necessary for flagellar motility. The protein sequence contains multiple potential phosphorylation sites, and the protein was confirmed to be phosphorylated in vivo. A yeast two-hybrid screen identified the testis-specific kinase, TSSK2, to be a potential duanyu1842G16L binding partner. duanyu1842G16L and TSSK2 interactions were confirmed by coimmunoprecipitation of both proteins from testis extracts and cell lysates expressing these proteins, and their colocalization was also noted by confocal microscopy in Chinese hamster ovary cells, where they were coexpressed. TSSK2 associates with duanyu1842G16L via its C-terminal domain bearing WD repeats. The N-terminal domain containing a coiled coil motif does not associate with TSSK2. duanyu1842G16L can be phosphorylated by TSSK2 in vitro. Finally, TSSK2 is absent or markedly reduced from the testes in most of the mice. These data support the conclusion that duanyu1842G16L is a TSSK2 substrate.

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