Valosin-containing protein/p97 interacts with sperm-activating and sperm-attracting factor (SAAF) in the ascidian egg and modulates sperm-attracting activity.
Sperm chemotaxis toward an egg is observed in many animals, and the control of sperm-attracting activity is thought to play an important role in ensuring fertilization. However, the mechanism underlying the release of a sperm attractant from an egg is still obscure. In this study, we examined the systems involved in the release of sperm-activating and sperm-attracting factor (SAAF), which is the sperm attractant of the ascidian Ciona intestinalis. Here, we show that the egg acquires sperm-attracting activity after germinal vesicle breakdown. Further, since the cytoplasmic extracts of immature oocytes exhibit no sperm-attracting activity, the SAAF in oocytes may be activated after germinal vesicle breakdown. We found 13 SAAF-binding proteins in an egg plasma membrane extract and identified five proteins by proteomic analysis: valosin-containing protein (VCP)/p97, proteasome alpha 2 subunit, MGC97756 protein, proteasome subunit Y, and beta-tubulin. In particular, the interaction between VCP/p97 and SAAF was confirmed by a pull-down assay. VCP/p97 is initially localized in the germinal vesicle, and during oocyte maturation, it shifts to the endoplasmic reticulum in the cortical regions. Thus, VCP/p97 is a potential modulator of SAAF release from the egg.
Kondoh
Eri
E
Misaki Marine Biological Station, Graduate School of Science, University of Tokyo, Miura 238-0225, Japan.
Konno
Aru
A
Inaba
Kazuo
K
Oishi
Tohru
T
Murata
Michio
M
Yoshida
Manabu
M
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002938:Ciona intestinalis / Q000378:metabolism*; D005260:Female; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D010063:Ovum / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D013083:Sperm Transport / Q000502:physiology; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism*; D000074405:Valosin Containing Protein
D018797:Cell Cycle Proteins; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C046951:valosin; D000251:Adenosine Triphosphatases; D000074405:Valosin Containing Protein