High molecular mass egg fucose sulfate polymer is required for opening both Ca2+ channels involved in triggering the sea urchin sperm acrosome reaction.
A linear fucose sulfate polymer (FSP), >10(6) daltons, is a major component of sea urchin egg jelly. FSP induces the sperm acrosome reaction (AR), an exocytotic process required for animal fertilization. Two Ca(2+) channels activate during AR induction, the first opens 1 s after FSP addition, and the second opens 5 s after the first. Mild acid hydrolysis of FSP results in a linear decrease in polymer size. The ability of FSP to induce the AR and activate sperm Ca(2+) channels decreases with increasing time of hydrolysis. Hydrolyzed FSP of approximately 60 kDa blocks intact FSP from inducing the AR. At 44 microg/ml hydrolyzed FSP, Ca(2+) entry into sperm is almost equal to that occurring in 3.8 microg/ml intact FSP; however the AR is not induced. The shape of the [Ca(2+)](i) increase curve and use of the Ca(2+) channel blockers nifidipine and Ni(2+) indicate that hydrolyzed FSP opens the second Ca(2+) channel, but not the first, and thus does not induce the AR. The giant size of intact FSP is required to open both Ca(2+) channels involved in triggering the AR.
Hirohashi
Noritaka
N
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202, USA. nhirohashi@ucsd.edu
Vacquier
Victor D
VD
D020101:Acrosome Reaction / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D005643:Fucose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006001:Glycoconjugates / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008297:Male; D008970:Molecular Weight; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D010063:Ovum / Q000737:chemistry* / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000378:metabolism; D012617:Sea Urchins / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism*; D013464:Sulfuric Acids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D006001:Glycoconjugates; D011956:Receptors, Cell Surface; D013464:Sulfuric Acids; C099881:egg jelly ligand receptors, Strongylocentrotus purpuratus; C061711:fucose-sulfate glycoconjugate; D005643:Fucose; D009532:Nickel; D009543:Nifedipine; D002118:Calcium