Bactericidal/Permeability-increasing protein is associated with the acrosome region of rodent epididymal spermatozoa.
To elucidate the molecular mechanisms involved in sperm maturation during epididymal transit, we intended to isolate secretory molecules that are region-specifically expressed along the epididymis and secreted into the lumen of epididymal ducts. By using differential display screening and DNA sequence analyses, we isolated a rat bactericidal/permeability-increasing protein (BPI) possessing a signal sequence at its N-terminal, which was expressed in the caput region of epididymis, but not in the caudal region. Reverse transcription polymerase chain reaction analysis and in situ hybridization showed that rat BPI messenger RNA (mRNA) was highly expressed in caput epididymal epithelium and that its expression level was developmentally up-regulated. Confocal laser scanning microscopy with the anti-BPI antibody revealed that in both rats and mice, BPI protein was detected on granulelike structures in the lumen of both caput and cauda epididymal ducts, as well as at the sperm surface covering the acrosome region in spermatozoa freshly isolated from epididymis. Acrosome reaction induced by calcium ionophore A23187 in vitro brought about the disappearance of BPI on mouse spermatozoa. These data suggested that BPI, which is synthesized in caput epididymis and secreted into the lumen, is associated with not only the granulelike structures, but also the sperm surface covering the acrosome region, and that BPI bound to the acrosome region is extinguished by acrosome reaction. Possibly BPI bound to the sperm surface covering the acrosome region in rodent spermatozoa is involved in sperm maturation or fertilization.
Yano
Rieko
R
Laboratory of Zoology, Graduate School of Agriculture, Kyushu University, Higashiku, Fukuoka 812-8581, Japan.
Matsuyama
Takuya
T
Kaneko
Takane
T
Kurio
Hitoshi
H
Murayama
Emi
E
Toshimori
Kiyotaka
K
Iida
Hiroshi
H
D000177:Acrosome / Q000378:metabolism*; D020101:Acrosome Reaction / Q000502:physiology*; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D004822:Epididymis / Q000378:metabolism*; D015870:Gene Expression; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D012333:RNA, Messenger; C021623:bactericidal permeability increasing protein