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A proton pump ATPase with testis-specific E1-subunit isoform required for acrosome acidification
Ge-Hong Sun-Wada1, Yoko Imai-Senga, Akitsugu Yamamoto
1Division of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Corp., Osaka 567-0047, Japan.
The Journal of Biological Chemistry
|March 2, 2002
Summary
Two novel vacuolar-type H(+)-ATPases (V-ATPases) subunit E isoforms, E1 and E2, were identified in mice. The testis-specific E1 isoform is crucial for acrosome acidification, essential for sperm development.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Vacuolar-type H(+)-ATPases (V-ATPases) are vital proton pumps in numerous physiological processes.
- Understanding V-ATPase subunit diversity is key to elucidating their specific functions.
Purpose of the Study:
- To identify and characterize novel V-ATPase subunit E isoforms in mice.
- To investigate the specific roles of these isoforms, particularly in spermatogenesis.
Main Methods:
- Gene identification and cloning of novel mouse V-ATPase subunit E isoforms (Atp6e1 and Atp6e2).
- Expression analysis using quantitative PCR and immunohistochemistry.
- Functional complementation assays in yeast and biochemical characterization of chimeric enzymes.
Main Results:
- Identified testis-specific E1 and ubiquitous E2 V-ATPase subunit E isoforms.
- E1 expression correlates with meiosis onset and is localized to developing acrosomes.
- Both E1 and E2 isoforms functionally complement yeast VMA4 mutations, confirming their roles as V-ATPase subunits.
Conclusions:
- The testis-specific E1 isoform is essential for acrosome acidification, a critical step in sperm maturation.
- The E1 isoform plays a vital role in energy coupling for proton transport within the acrosome.
- The distinct expression patterns of E1 and E2 highlight isoform-specific functions within the V-ATPase family.