Insights into the Mechanism of ADP Action on Flagellar Motility Derived from Studies on Bull Sperm
| Autor: | Dominic W. Pelle, Kathleen A. Lesich, Charles B. Lindemann |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Male
Sodium Vanadate Dynein Biophysics Beat (acoustics) Biology Flagellum Models Biological chemistry.chemical_compound Animals Computer Simulation Flagellar motility Sperm motility Dose-Response Relationship Drug urogenital system Spermatozoa Sperm Adenosine Diphosphate Adenosine diphosphate Torque chemistry Biochemistry Flagella Cell Biophysics Sperm Motility Cattle |
| Zdroj: | Biophysical Journal. 95(1):472-482 |
| ISSN: | 0006-3495 |
| DOI: | 10.1529/biophysj.107.127951 |
| Popis: | Adenosine diphosphate (ADP) is known to have interesting effects on flagellar motility. Permeabilized and reactivated bull sperm exhibit a marked reduction in beating frequency and a greatly increased beat amplitude in the presence of 1-4 mM ADP. In this study we examined the force production of sperm reactivated with 0.1 mM ATP with and without 1 mM ADP and found that there is little or no resulting change in the stalling force produced by a bull sperm flagella in response to ADP. Because bull sperm bend to a higher curvature after ADP treatment we explored the possibility that ADP-treated sperm flagella are more flexible. We measured the stiffness of 50 mM sodium vanadate treated bull sperm in the presence of 4 mM ADP, but found no change in the passive flagellar stiffness. When we analyzed the torque that develops in ADP-treated sperm at the point of beat reversal we found that the torque developed by the flagellum is significantly increased. Our torque estimates also allow us to calculate the transverse force (t-force) acting on the flagellum at the point of beat direction reversal. We find that the t-force at the switch-point of the beat is increased significantly in the ADP treated condition, averaging 0.7 6 0.29 nN/m mi n 0.1 mM ATP and increasing to 2.9 6 1.2 nN/mm in 0.1 mM ATP plus 4 mM ADP. This suggests that ADP is exerting its effect on the beat by increasing the tenacity of dynein attachment at the B-subtubule. This could be a direct result of a regulatory effect of ADP on the binding affinity of dynein for the B-subtubule of the outer doublets. This result could also help to explain a number of previous experimental observations, as discussed. duced (7). These results suggest that the reduced beating frequency in ADP-treated sperm could be explained by a reductioninthevelocityofmicrotubuleslidinginADP-treated flagella. Paradoxically, Yagi (8) reported that inner arm dyneins actually improve their ability to translocate micro- tubules in the presence of ADP as compared to ATP alone. In line with this it has also been reported that the completeness of the disintegration is actually increased in the presence of ADP (9). This seems, at least superficially, to counter the slowing action of ADP on intact doublet sliding rates, and suggests amechanism bywhich aselective effect ontheinner arms could actually have a strengthening effect on beating amplitude and a positive effect on coordinated beating. |
| Databáze: | OpenAIRE |
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