Department of Biological Sciences, Kent State University, Kent, Ohio.
Laboratory of Signal Transduction, Department of Medical Sciences, Institute of Biomedicine-iBiMED, University of Aveiro, Aveiro, Portugal.
J Cell Physiol. 2019 Mar;234(3):3105-3118. doi: 10.1002/jcp.27130. Epub 2018 Aug 25.
The serine/threonine protein phosphatase 1 (PP1) inhibitors PPP1R2, PPP1R7, and PPP1R11 are evolutionarily ancient and highly conserved proteins. Four PP1 isoforms, PP1α, PP1β, PP1γ1, and PP1γ2, exist; three of them except PP1γ2 are ubiquitous. The fact that PP1γ2 isoform is present only in mammalian testis and sperm led to the notion that isoform-specific regulators for PP1γ2 in sperm may be responsible for its function. In this report, we studied these inhibitors, PPP1R2, R7, and R11, to determine their spatial and temporal expression in testis and their regulatory functions in sperm. We show that, similar to PP1γ2, the three inhibitors are expressed at high levels in developing spermatogenic cells. However, the transcripts for the regulators are expressed as unique sizes in testis compared with somatic tissues. The three regulators share localization with PP1γ2 in the head and the principal piece of sperm. We show that the association of inhibitors to PP1γ2 changes during epididymal sperm maturation. In immotile caput epididymal sperm, PPP1R2 and PPP1R7 are not bound to PP1γ2, whereas in motile caudal sperm, all three inhibitors are bound as heterodimers or heterotrimers. In caudal sperm from male mice lacking sAC and glycogen synthase kinase 3, where motility and fertility are impaired, the association of PP1γ2 to the inhibitors resembles immature caput sperm. Changes in the association of the regulators with PP1γ2, due to their phosphorylation, are part of biochemical mechanisms responsible for the development of motility and fertilizing ability of sperm during their passage through the epididymis.
丝氨酸/苏氨酸蛋白磷酸酶 1（PP1）抑制剂 PPP1R2、PPP1R7 和 PPP1R11 是进化上古老且高度保守的蛋白质。存在四种 PP1 同工型，即 PP1α、PP1β、PP1γ1 和 PP1γ2，其中除 PP1γ2 外，其他三种同工型普遍存在。PP1γ2 同工型仅存在于哺乳动物睾丸和精子中，这一事实表明，精子中 PP1γ2 的同工型特异性调节剂可能负责其功能。在本报告中，我们研究了这些抑制剂 PPP1R2、R7 和 R11，以确定它们在睾丸中的时空表达及其在精子中的调节功能。我们表明，与 PP1γ2 相似，三种抑制剂在发育中的精原细胞中高水平表达。然而，与体细胞组织相比，调节剂的转录物在睾丸中以独特的大小表达。这三种调节剂与 PP1γ2 在精子头部和主段中具有相同的定位。我们表明，抑制剂与 PP1γ2 的结合在附睾精子成熟过程中发生变化。在无动力的附睾头精子中，PPP1R2 和 PPP1R7 与 PP1γ2 不结合，而在有动力的附睾尾精子中，所有三种抑制剂都作为异二聚体或异三聚体结合。在缺乏 sAC 和糖原合酶激酶 3 的雄性小鼠的附睾尾精子中，运动性和生育能力受损，PP1γ2 与抑制剂的结合类似于未成熟的附睾头精子。由于磷酸化，调节剂与 PP1γ2 的结合变化是负责精子在通过附睾时运动性和受精能力发育的生化机制的一部分。
