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Activation of Ca 2+ Transport System of Sea Urchin Sperm by High External pH: 220 kD Membrane Glycoprotein is Involved in the Regulation of the Ca 2+ Entry
Author(s) -
Sendai Yutaka,
Aketa Kenji
Publication year - 1991
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.1991.00101.x
Subject(s) - sea urchin , chemistry , acrosome reaction , hemicentrotus , sperm , wheat germ agglutinin , biophysics , ruthenium red , biochemistry , verapamil , lectin , calcium , microbiology and biotechnology , biology , botany , organic chemistry , in vitro
When sperm of the sea urchin, Hemicentrotus pulcherrimus , were exposed to high pH (9.0) sea water, they showed large increases in intracellular Ca 2+ ([Ca 2+ ]i) and pH (pHi) and underwent the acrosome reaction (AR) without the aid of the egg jelly. Not only [Ca 2+ ]i increase but also pHi rise did not occur under Ca 2+ ‐free conditions. Both the increases in [Ca 2+ ]i and pHi and the AR by high pH were inhibited by a Ca 2+ channel blockers, verapamil and nisoldipine, and by a lectin, wheat germ agglutinin (WGA) which interacts with a 220 kD membrane glycoprotein of sperm. These reagents inhibited also the AR by the egg jelly. The inhibitory effects of WGA were immediately canceled by the addition of N‐acetyl‐D‐glucosamine, a sugar which is known to remove WGA from its binding site. These results suggest that 1) the same Ca 2+ transport system is activated by high external pH and the egg jelly, 2) increase in [Ca 2+ ]i is prerequisite for the stimulation of the H + ‐efflux system(s) and 3) the 220 kD WGA‐binding membrane protein functions as a regulator protein of Ca 2+ transport system.