• PMID: 20731842
• Gene Name: CABYR
• Condition: Participates in the assembly of complexes in the Fibrous sheath
• Association: Associated
• Sex: Male
• Infertility type: Male infertility
• Other associated phenotypes: Participates in the assembly of complexes in the Fibrous sheath

CABYR isoforms expressed in late steps of spermiogenesis bind with AKAPs and ropporin in mouse sperm fibrous sheath

Li YF, He W, Kim YH, Mandal A, Digilio L, Klotz K, Flickinger CJ, Herr JC.

BACKGROUND: CABYR is a polymorphic calcium-binding protein of the sperm fibrous sheath (FS) which gene contains two coding regions (CR-A and CR-B) and is tyrosine as well as serine/threonine phosphorylated during in vitro sperm capacitation. Thus far, the detailed information on CABYR protein expression in mouse spermatogenesis is lacking. Moreover, because of the complexity of this polymorphic protein, there are no data on how CABYR isoforms associate and assemble into the FS. METHODS: The capacity of mouse CABYR isoforms to associate into dimers and oligomers, and the relationships between CABYR and other FS proteins were studied by gel electrophoresis, Western blotting, immunofluorescence, immunoprecipitation and yeast two-hybrid analyses. RESULTS: The predominant form of mouse CABYR in the FS is an 80 kDa variant that contains only CABYR-A encoded by coding region A. CABYR isoforms form dimers by combining the 80 kDa CABYR-A-only variant with the 50 kDa variant that contains both CABYR-A and CABYR-B encoded by full length or truncated coding region A and B. It is proposed that this step is followed by the formation of larger oligomers, which then participate in the formation of the supramolecular structure of the FS in mouse sperm. The initial expression of CABYR occurs in the cytoplasm of spermatids at step 11 of spermiogenesis and increases progressively during steps 12-15. CABYR protein gradually migrates into the sperm flagellum and localizes to the FS of the principal piece during steps 15-16. Deletion of the CABYR RII domain abolished the interaction between CABYR and AKAP3/AKAP4 but did not abolish the interaction between CABYR and ropporin suggesting that CABYR binds to AKAP3/AKAP4 by its RII domain but binds to ropporin through another as yet undefined region. CONCLUSIONS: CABYR expresses at the late stage of spermiogenesis and its isoforms oligomerize and bind with AKAPs and ropporin. These interactions strongly suggest that CABYR participates in the assembly of complexes in the FS, which may be related to calcium signaling. FAU - Li, Yan-Feng AU - Li YF AD - Department of Urology, Daping Hospital, Institute of Surgery Research, Third Military Medical University, Chongqing, PR China. lyf1000@yahoo.com.cn FAU - He, Wei AU - He W FAU - Kim, Young-Hwan AU - Kim YH FAU - Mandal, Arabinda AU - Mandal A FAU - Digilio, Laura AU - Digilio L FAU - Klotz, Ken AU - Klotz K FAU - Flickinger, Charles J AU - Flickinger CJ