FSCB, a Novel Protein Kinase A-phosphorylated Calcium-binding Protein, Is a CABYR-binding Partner Involved in Late Steps of Fibrous Sheath Biogenesis

We report characterization of a novel testis- and sperm-specific protein, FSCB (fibrous sheath CABYR binding), that is expressed post-meiotically and localized in mouse sperm flagella. FSCB was identified as a binding partner of CABYR, a calcium-binding protein that is tyrosine-phosphorylated during...

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Bibliographic Details
Published in:The Journal of biological chemistry 2007-11, Vol.282 (47), p.34104-34119
Main Authors: Li, Yan-Feng, He, Wei, Jha, Kula N., Klotz, Ken, Kim, Young-Hwan, Mandal, Arabinda, Pulido, Silvia, Digilio, Laura, Flickinger, Charles J., Herr, John C.
Format: Article
Language:English
Subjects:
Amino Acid Motifs - genetics
Animals
Base Sequence
Calcium - metabolism
Calcium-Binding Proteins - biosynthesis
Calcium-Binding Proteins - genetics
Calcium-Binding Proteins - metabolism
Cyclic AMP-Dependent Protein Kinases - metabolism
Humans
Male
Mice
Molecular Sequence Data
Phosphoproteins - genetics
Phosphoproteins - metabolism
Phosphorylation
Rats
Sperm Capacitation - physiology
Sperm Tail - metabolism
Sperm Tail - ultrastructure
Spermatids - metabolism
Spermatids - ultrastructure
Spermatogenesis - physiology
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Summary:We report characterization of a novel testis- and sperm-specific protein, FSCB (fibrous sheath CABYR binding), that is expressed post-meiotically and localized in mouse sperm flagella. FSCB was identified as a binding partner of CABYR, a calcium-binding protein that is tyrosine-phosphorylated during capacitation. Orthologous genes of FSCB are present in other mammals, including rat and human, and conserved motifs in FSCB include PXXP, proline-rich and extensin-like regions. FSCB is phosphorylated by protein kinase A as shown by in vitro phosphorylation assay and also by determining phosphorylation sites in native FSCB from mouse sperm. Calcium overlay assay showed that FSCB is a calcium-binding protein from sperm. FSCB is a post meiotic protein first expressed at step 11 of mouse spermatogenesis in the elongating spermatids, and it subsequently incorporates into the flagellar principal piece of the sperm. Ultrastructurally, FSCB localized to a cortical layer of intermediate electron density at the surface of the ribs and longitudinal columns of the fibrous sheath. Due to its temporal appearance during spermiogenesis and location at the cortex of the fibrous sheath, FSCB is postulated to be involved in the later stages of fibrous sheath assembly.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M702238200