Abstract
Sperm motility is essential for the natural fertilization process in most animal species. Despite the fact that evolution took place under conditions of constant gravity, the motility of spermatozoa of insects and mammals under microgravity conditions changes in different ways. In this work, an attempt was made to explain this effect. The sperm motility of the fruit fly Drosophila melanogaster and the mouse was evaluated after exposure to a random positioning machine for 6 h. Sodium fluoride was used to inhibit serine/threonine phosphatases, sodium orthovanadate was used to inhibit tyrosine phosphatases, and 6-(dimethylamino)purine was used to inhibit protein kinases. The results obtained indicate that simulated microgravity leads to an increase in the speed of movement of fly spermatozoa by 30% (p < 0.05), and this effect is blocked by sodium fluoride. In contrast, a 29% (p < 0.05) decrease in the speed of movement of mouse spermatozoa under simulated microgravity is prevented by 6-(dimethylamino)purine. Moreover, after 6 h of exposure, the content of tubulin cytoskeleton and actin proteins remains at the control level in the spermatozoa of flies and mice. However, the content of the actin-binding protein alpha-actinin in fly sperm decreases by 29% (p < 0.05), while in mouse sperm, the relative content of alpha-actinin1 increases by 94% (p < 0.05) and alpha-actinin4 by 121% (p < 0.05) relative to the control, as determined by 6 simulated microgravity tests. It can be assumed that the effect of simulated microgravity on the motility of mammalian spermatozoa is mediated through the regulation of phosphorylation and that of insects through the regulation of dephosphorylation of motor proteins; moreover, the development of a response to changes in external mechanical conditions has a different time scale.
Highlights
The motor activity of spermatozoa, which is a prerequisite for successful fertilization in most animal species, is provided by the structure of the cytoskeleton of their tails, called the axoneme
6-(dimethylamino)purine (6-DMAP) for a wide range of kinases), we showed that under microgravity, changes in the motor activity of higher and lower animals can be associated with differential regulation of the dynamic equilibrium of phosphorylation-dephosphorylation
According to the UniProt database, dynein has a large number of phosphorylation sites, both for tyrosine and for serine and threonine, which significantly increases the number of possible regulatory pathways
Summary
The motor activity of spermatozoa, which is a prerequisite for successful fertilization in most animal species, is provided by the structure of the cytoskeleton of their tails, called the axoneme. The axoneme is a system of microtubules formed by tubulin heterodimers according to the 9 + 2 scheme, of which 2 are central singlet microtubules, and 9 are peripheral doublets (A and B microtubules). Dynein is a motor protein that moves towards the minus end of microtubules due to hydrolysis of ATP, ensuring the movement of the flagellum [2]. Despite the high homology of structural proteins and the constant gravity during the evolutionary process, with changes in gravity, the motor activity of spermatozoa in lower and higher animals changes in different ways
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