Document Detail

Extracellular ubiquitination and proteasome-mediated degradation of the ascidian sperm receptor.
MedLine Citation:
PMID:  11818546     Owner:  NLM     Status:  MEDLINE    
The ubiquitin-proteasome system is essential for intracellular protein degradation, but an extracellular role of this system has not been known until now. We have previously reported that the proteasome is secreted into the surrounding seawater from sperm of the ascidian (Urochordata) Halocynthia roretzi on sperm activation, and that the sperm proteasome plays a key role in fertilization. Here, we show that a 70-kDa component (HrVC70) of the vitelline coat is the physiological substrate for the ubiquitin-proteasome system during fertilization of H. roretzi. A cDNA clone encoding the HrVC70 precursor (HrVC120) was isolated, and a homology search revealed that HrVC120 contains 13 epidermal growth factor-like repeats and a mammalian zona pellucida glycoprotein-homologous domain. HrVC70 functions as a sperm receptor. We demonstrate that HrVC70 is ubiquitinated both in vitro and in vivo. The immunocytochemical localization of multiubiquitin chains in the vitelline coat and the inhibitory effect of monoclonal antibodies against the multiubiquitin chains on fertilization strongly support the role of the ubiquitin-proteasome system in ascidian fertilization. Taken together, these results indicate that the ubiquitin-proteasome system is responsible for extracellular degradation of the sperm receptor HrVC70 and, consequently, for sperm penetration of the vitelline coat during fertilization.
Hitoshi Sawada; Naoyuki Sakai; Yukichi Abe; Etsuko Tanaka; Youko Takahashi; Junko Fujino; Eri Kodama; Satoshi Takizawa; Hideyoshi Yokosawa
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2002-01-29
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  99     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2002 Feb 
Date Detail:
Created Date:  2002-02-06     Completed Date:  2002-03-07     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1223-8     Citation Subset:  IM    
Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812 Japan.
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MeSH Terms
Amino Acid Sequence
Cloning, Molecular
Cysteine Endopeptidases / metabolism*
Extracellular Space / physiology
Molecular Sequence Data
Multienzyme Complexes / metabolism*
Mutagenesis, Site-Directed
Proteasome Endopeptidase Complex
Receptors, Cell Surface / chemistry,  genetics,  metabolism*
Recombinant Fusion Proteins / chemistry,  metabolism
Recombinant Proteins / chemistry,  metabolism
Sequence Alignment
Sequence Homology, Amino Acid
Sperm-Ovum Interactions / physiology
Ubiquitin / metabolism*
Urochordata / physiology*
Vitelline Membrane / physiology
Reg. No./Substance:
0/Multienzyme Complexes; 0/Receptors, Cell Surface; 0/Recombinant Fusion Proteins; 0/Recombinant Proteins; 0/Ubiquitin; 0/egg surface sperm receptor; EC 3.4.22.-/Cysteine Endopeptidases; EC Endopeptidase Complex

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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