Signal transduction mechanisms for the regulation of sperm motility

独特的是，禽类精子表现出可逆的、依赖于温度的运动抑制现象：在体外的简单盐溶液中，它们在禽类体温为40-41ﾟC时不活动，但在降温至30ﾟC时恢复运动。然而，参与运动调节的细胞内分子级联仍有待确定。细胞内游离Ca~(2+)似乎是维持运动能力所必需的，因为在40ﾟC时，添加Ca~(2+)&gt；可恢复完整精子的运动能力。此外，在30ﾟ℃下，含有胞内Ca~(2+)和AM的完整精子的活力可以忽略不计，但可以通过随后添加Ca~(2+)和Ca~(2+)而立即恢复。然而，即使在有Ca~(2+)存在的情况下，添加钙调素拮抗剂，如W-7和三氟拉嗪，在30ﾟC和40ﾟ时抑制精子的活力。存在于鸡精子轴丝中的蛋白磷酸酶1(Pp1)的激活可能与…有关。在40ﾟC时，对鸡精子活力的抑制作用大于对精子活力的抑制，因为在40ﾟC时，除花盏花素A和冈田酸外，PP1的特异性抑制剂1和2也能刺激去膜精子的活力。/钙调素依赖的蛋白激酶，因为在加入MLCK的特异性抑制剂ML-9后，完整的和去膜的鸡精子在30ﾟC时的活力都显著降低，但在加入特异性抑制剂H-8或cAMP依赖的蛋白激酶后并不显著。在30 kDa的蛋白质中观察到了显著的磷酸化差异。在加入PKA底物多肽Kemptie和对照样品后，该蛋白被强烈磷酸化，但在存在肌球蛋白轻链激酶底物多肽的情况下，该蛋白仅轻微磷酸化。这些结果表明，钙/钙调蛋白依赖蛋白激酶的磷酸化可能是维持鸡精子活力的调节步骤，而不是PKA，MLCK或类似肌球蛋白轻链激酶的蛋白对30ﾟ的蛋白的磷酸化可能参与了30 kDa的鞭毛运动的调节。

Uniquely, fowl spermatozoa display the phenomenon of reversible, temperature-dependent motility inhibition : in simple salt solutions in vitro, they are immotile at the avian body temperature of 40-41ﾟC,but regain motility on reduction of the temperature to 30ﾟC.However, the intracellular molecular cascades involved in the regulation of motility remain to be determined.Intracellular free Ca^<2+> seems to be essential for the maintenance of motility, since the motility of intact spermatozoa at 40ﾟC can be restored by the addition of Ca^<2+>. Furthermore, the motility of intact spermatozoa loaded with an intracellular Ca^<2+> chelator, BAPTA/AM is negligible at 30ﾟC,but can be instantly restored by the subsequent addition of Ca^<2+>. However, even in the presence of Ca^<2+>, the addition of calmodulin antagonists such as W-7 and trifluoperazine inhibited sperm motility at 30ﾟC and 40ﾟCThe activation of protein phosphatase type 1 (PP1), present in the fowl sperm axoneme, may be involved i … More n the inhibition of fowl sperm motility at 40ﾟC,since, in addition to calyculin A and okadaic acid, specific inhibitors of PP1, inhibitors 1 and 2, also stimulated the motility of demembranated spermatozoa at 40ﾟC.Furthermore, the involvement of myosin light chain kinase (MLCK), or a MLCK-like protein, has been proposed to be a candidate of Ca^<2+>/calmodulin dependent protein kinase, since the motility of both intact and demembranated fowl spermatozoa at 30ﾟC decreased markedly following the addition of ML-9, a specific inhibitor of MLCK,but not following the addition of H-8, a specific inhibitor or cAMP-dependent protein kinase (PKA). A marked difference in phosphorylation was observed in a 30 kDa protein. This protein was strongly phosphorylated after the addition of Kemptide, a PKA substrate peptide as well as control samples but only slightly phosphorylated in the presence of a myosin light chain kinase (MLCK) substrate peptide.These results suggest that phosphorylation by Ca^<2+>/calmodulin-dependent protein kinases, rather tha PKA,is likely to be a regulatory step in the maintenance of fowl sperm motility, and that phosphorylation of a 30 kDa protein by MLCK or a MLCK-like proteinis may be involved in the regulation of flagellar movement at 30ﾟC. Less