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Complement C4b-binding protein as a novel murine epididymal secretory protein
Mayumi I Nonaka1, Yoshitaka Hishikawa, Nobuo Moriyama
1Department of Biological Sciences, University of Tokyo, Tokyo 133-0033, Japan. nmayumi@biol.s.u-tokyo.ac.jp
Biology of Reproduction
|August 22, 2003
Summary
Complement C4b-binding protein (C4BP) is synthesized in the epididymis and binds to sperm. This study reveals C4BP
Area of Science:
- Immunology
- Reproductive Biology
- Molecular Biology
Background:
- Complement C4b-binding protein (C4BP) regulates the complement system.
- C4BP alpha chain (C4BPalpha) mRNA is expressed in the epididymis in an androgen-dependent manner.
Purpose of the Study:
- To analyze the murine C4bpa gene and investigate C4BP localization and function in the epididymis.
Main Methods:
- Gene analysis of murine C4bpa.
- Immunohistochemistry using anti-C4BP antiserum.
- Indirect immunofluorescence and immunoelectron microscopy on spermatozoa.
Main Results:
- Epididymal and liver C4BPalpha mRNAs originate from a single gene but use distinct transcription start sites.
- C4BP is localized in epididymal epithelial cells and on sperm surfaces (head region) from distal caput to cauda.
- C4BP is found on sperm plasma and outer acrosomal membranes.
Conclusions:
- Epididymal C4BP is synthesized, secreted in a region-specific manner, and acquired by sperm during passage.
- C4BP functions as an epididymal secretory protein potentially involved in sperm maturation.