Real-time analysis of the role of Ca(2+) in flagellar movement and motility in single sea urchin sperm.
Eggs of many marine and mammalian species attract sperm by releasing chemoattractants that modify the bending properties of flagella to redirect sperm paths toward the egg. This process, called chemotaxis, is dependent on extracellular Ca(2+). We used stroboscopic fluorescence imaging to measure intracellular Ca(2+) concentration ([Ca(2+)]i) in the flagella of swimming sea urchin sperm. Uncaging of cyclic GMP induced Ca(2+) entry via at least two distinct pathways, and we identified a nimodipine-sensitive pathway, compartmentalized in the flagella, as a key regulator of flagellar bending and directed motility changes. We found that, contrary to current models, the degree of flagellar bending does not vary in proportion to the overall [Ca(2+)]i. Instead we propose a new model whereby flagella bending is increased by Ca(2+) flux through the nimodipine-sensitive pathway, and is unaffected by [Ca(2+)]i increases through alternative pathways.
Wood
Christopher D
CD
Department of Developmental Genetics and Molecular Physiology, Institute of Biotechnology, National Autonomous University of Mexico, Cuernavaca, Morelos 62210, Mexico. chris@ibt.unam.mx
Nishigaki
Takuya
T
Furuta
Toshiaki
T
Baba
Shoji A
SA
Darszon
Alberto
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism; D005306:Fertilization / Q000502:physiology; D005407:Flagella / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*; D047270:Strongylocentrotus purpuratus / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D006152:Cyclic GMP; D002118:Calcium