Valosin‐containing protein/p97 interacts with sperm‐activating and sperm‐attracting factor (SAAF) in the ascidian egg and modulates sperm‐attracting activity

Abstract

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.

Transcriptome Analysis Reveals Strain-Specific and Conserved Stemness Genes in Schmidtea mediterranea

“…These results are consistent with earlier findings that planarian small RNAs exhibit differential patterns of expression in sexual and asexual strains [10], [49]. Using RT-PCR, we verified the strain-specific expression of genes likely to play roles in sexual reproduction, and found that the gene encoding a homolog of Vcp/p97 (valosin-containing protein/p97 (CUFF.138192.0)) , which has been implicated in sexual reproduction by way of sperm-attracting activity in ascidians [56], is expressed specifically in sexual animals (Figure 2B). We also found that Smed-hnRNPA2 (CUFF.177545.0) , which encodes a homolog of hnRNPA2, and Smed-rap55 (CUFF.414275.0) , which encodes a RAP55 homolog, are much more strongly expressed in sexual animals than asexual animals (Figure 2B).…”

Calcium Channels in the Development, Maturation, and Function of Spermatozoa

“…Spermatozoa of the sea squirt Ciona intestinalis display clear chemotaxis in response to gradients of a sulfated steroid named SAAF (sperm-activating and attracting factor), which is released only from unfertilized mature oocytes (296,576,578). Since the SAAF receptor has not been identified, the signaling mechanism is not well characterized.…”

Characterization, expression and localization of valosin-containing protein in ovaries of the giant tiger shrimp Penaeus monodon

“…After GVBD, the protein was observed in the nucleo-cytoplasmic compartment, the cytoskeletal architecture and the plasma membrane of oocytes. Similarly, p97/VCP in Ciona was reported to be localized first in the endoplasmic reticulum (ER) region and cortical region of oocytes, later in the germinal vesicle (GV) and finally in the cortical ER region after GVBD (Kondoh et al, 2008).…”

“…Characterization of p97/VCP/ Cdc48-depleted embryos and oocytes revealed that this protein was required not only for progression of meiotic metaphase I but also for chromosome condensation at the diakinesis phase in meiotic prophase I (Sasagawa et al, 2007). Kondoh et al (2008) studied binding proteins of sperm-activating and sperm-attracting factor (SAAF) in eggs of the ascidian (Ciona intestinalis). A total of 13 SAAF-binding proteins were found in an egg plasma membrane extract and five were further analyzed by proteomic analysis: p97/VCP/Cdc48, proteasome alpha 2 subunit, MGC97756 protein, proteasome subunit Y and β-tubulin.…”

“…Valosin-containing protein (VCP also known as p97 in mammals, Cdc48 in yeast, TER94 in insects and VAT in archaea) (Kondoh et al, 2008) belongs to the ATPase-associated with diverse cellular activity (AAA) family of ATPase (Bug and Meyer, 2012). VCP is a highly conserved protein in eukaryotes.…”