Involvement of Rabphilin-3A in cortical granule exocytosis in mouse eggs

J Cell Biol. 1996 Dec;135(6 Pt 2):1741-7. doi: 10.1083/jcb.135.6.1741.


Rabphilin-3A is a putative target protein for Rab3A, a member of the small GTP-binding protein superfamily that has been suggested to play a role in regulated exocytosis in presynapses. In this study we determined the expression and the function of Rabphilin-3A in mouse eggs at fertilization. Rabphilin-3A mRNA and protein were detected by reverse transcriptase-PCR and immunoblot analysis, respectively, in metaphase II mouse eggs. Immunofluorescence analysis showed that Rabphilin-3A protein was distributed in the cortical region in eggs. Sperm induces cortical granule (CG) exocytosis via an increase in cytosolic Ca2+ at fertilization. We microinjected the NH2- or COOH-terminal fragment of recombinant Rabphilin-3A into metaphase II eggs. Neither treatments altered the sperm-induced cytosolic Ca2+ increase, but both inhibited CG exocytosis in a dose-dependent manner. The NH2-terminal fragment was more effective than the COOH-terminal fragment. Full-length Rabphilin-3A did not affect CG exocytosis, but it attenuated the inhibition of CG exocytosis by the NH2-terminal fragment. These results show that Rabphilin-3A is involved in Ca(2+)-dependent CG exocytosis at fertilization in mouse eggs.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Calcium / metabolism
  • Cytoplasmic Granules / physiology*
  • Exocytosis / drug effects
  • Exocytosis / physiology*
  • Female
  • Fertilization / physiology
  • GTP-Binding Proteins / analysis
  • GTP-Binding Proteins / genetics*
  • Gene Expression / physiology
  • Glutathione Transferase / pharmacology
  • Hemagglutinins / pharmacology
  • Male
  • Metaphase / physiology
  • Mice
  • Mice, Inbred Strains
  • Molecular Sequence Data
  • Nerve Tissue Proteins / analysis
  • Nerve Tissue Proteins / genetics*
  • Ovum / chemistry*
  • Ovum / cytology
  • Ovum / physiology
  • Peptide Fragments / pharmacology
  • RNA, Messenger / metabolism
  • Signal Transduction / physiology
  • Vesicular Transport Proteins
  • rab GTP-Binding Proteins*


  • Adaptor Proteins, Signal Transducing
  • Hemagglutinins
  • Nerve Tissue Proteins
  • Peptide Fragments
  • RNA, Messenger
  • Vesicular Transport Proteins
  • rabphilin-3A
  • Glutathione Transferase
  • GTP-Binding Proteins
  • rab GTP-Binding Proteins
  • Calcium

Associated data

  • GENBANK/D29965