Proteomics of ionomycin-induced ascidian sperm reaction: Released and exposed sperm proteins in the ascidian Ciona intestinalis

• Published in: Proteomics (Weinheim) Vol. 15; no. 23-24; pp. 4064 - 4079
• Main Authors: Nakazawa, Shiori, Shirae-Kurabayashi, Maki, Otsuka, Kei, Sawada, Hitoshi
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 01.12.2015; Wiley Subscription Services, Inc
• Subjects: Animals; Ascidian; Calcium Ionophores - pharmacology; Cell biology; Ciona intestinalis; Ciona intestinalis - drug effects; Ciona intestinalis - metabolism; Fertilization; Ionomycin - pharmacology; Male; Protease; Proteasome; Proteasome Endopeptidase Complex - metabolism; Proteins; Proteomics; Sperm; Spermatozoa - drug effects; Spermatozoa - metabolism; Ubiquitin; Ubiquitin - metabolism; Ubiquitin; Cell biology; Fertilization; Ascidian; Protease; Proteasome
• ISSN: 1615-9853; 1615-9861
• DOI: 10.1002/pmic.201500162

Sperm proteins mediating sperm–egg interaction should be exhibited on the sperm surface, or exposed or released when sperm approach an egg. In ascidians (protochordates), sperm undergo a sperm reaction, characterized by enhanced sperm motility and mitochondrial swelling and shedding on contact with the vitelline coat (VC) or by treatment with Ca2+ ionophore. Here, proteomic analysis was conducted on sperm exudates and sperm surface proteins using ionomycin‐induced sperm reaction and cell‐impermeable labeling in Ciona intestinalis type A (C. robusta). In the exudate from sperm treated with ionomycin, membrane proteins including a possible VC receptor CiUrabin were abundant, indicating the release of membranous compartments during sperm reaction. Among the surface proteins XP_009859314.1 (uncharacterized protein exhibiting homology to HrTTSP‐1) was most abundant before the sperm reaction, but XP_004227079.1 (unknown Ig superfamily protein) appears to be most abundantly exposed by the sperm reaction. Moreover, proteins containing a notable set of domains, astacin‐like metalloprotease domain and thrombospondin type 1 repeat(s), were found in this fraction. Possible roles in fertilization as well as localizations and behaviors of these proteins are discussed.