Fraser L R, Hanyaloglu A, Cockle S M
King's College London, Strand, London, United Kingdom.
Mol Reprod Dev. 1997 Dec;48(4):529-35. doi: 10.1002/(SICI)1098-2795(199712)48:4<529::AID-MRD14>3.0.CO;2-O.
Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2), a tripeptide structurally related to thyrotrophin releasing hormone (TRH; pGlu-His-ProNH2), is present in the prostate gland and seminal plasma of several mammalian species. FPP has been shown not only to stimulate the capacitation and fertilizing ability of epididymal mouse and ejaculated human spermatozoa, but also to inhibit spontaneous acrosome loss in mouse spermatozoa. These results suggest a possible role in vivo for FPP to maximize the fertilizing potential of the few cells that reach the ampulla. In this study we have investigated the effects of FPP-related peptides on mouse sperm capacitation and the acrosome reaction (using chlortetracycline fluorescence) and in vitro fertilizing ability. Deamidated FPP neither stimulated capacitation when tested at 50-200 nM nor interfered with FPP's stimulation of capacitation. Three neutral peptides (pGlu-Phe-ProNH2, MeO-FPP, pGlu-Gln-ProNH2) were also evaluated. pGlu-Phe-ProNH2, slightly stimulatory when used alone, had no additive effect when used in combination with FPP and the methyl derivative of FPP had no bioactivity itself and did not inhibit responses to FPP. In marked contrast, pGlu-Gln-ProNH2 (Gln-FPP), which had no bioactivity when added to uncapacitated suspensions at 50-100 nM, significantly inhibited FPP's stimulation of capacitation and fertilizing ability in vitro. Furthermore, when Gln-FPP + FPP were added to capacitated suspensions, Gln-FPP prevented FPP's inhibition of spontaneous acrosome loss. Our recent studies have indicated that FPP and adenosine can elicit similar responses but appear to act at different sites. The fact that Gln-FPP inhibited responses to FPP, but not to adenosine, indicates that Gln-FPP is acting at an FPP-specific site. We, therefore, conclude that the specific structure of the FPP molecule is crucial for biological activity. Removal of the terminal amide group abolishes bioactivity and changes to the central amino acid can have significant functional consequences. Since Gln-FPP is a candidate intermediate peptide in the FPP biosynthetic pathway and has been identified in human semen, abnormality in prostate function could lead to release of Gln-FPP along with, or instead of, FPP. Our results suggest that the relative proportions of FPP and related peptides in seminal plasma could have a significant effect on fertility in vivo.
促受精肽（FPP；焦谷氨酸 - 谷氨酸 - 脯氨酰胺）是一种结构上与促甲状腺激素释放激素（TRH；焦谷氨酸 - 组氨酸 - 脯氨酰胺）相关的三肽，存在于多种哺乳动物的前列腺和精浆中。研究表明，FPP不仅能刺激附睾小鼠和射出的人类精子的获能及受精能力，还能抑制小鼠精子的自发顶体反应丧失。这些结果表明，FPP在体内可能具有使到达壶腹的少数细胞的受精潜力最大化的作用。在本研究中，我们研究了FPP相关肽对小鼠精子获能、顶体反应（使用金霉素荧光法）及体外受精能力的影响。脱酰胺FPP在50 - 200 nM浓度下测试时既不刺激获能，也不干扰FPP对获能的刺激作用。还评估了三种中性肽（焦谷氨酸 - 苯丙氨酸 - 脯氨酰胺、甲氧基 - FPP、焦谷氨酸 - 谷氨酰胺 - 脯氨酰胺）。焦谷氨酸 - 苯丙氨酸 - 脯氨酰胺单独使用时略有刺激作用，与FPP联合使用时无相加作用，FPP的甲基衍生物本身无生物活性，也不抑制对FPP的反应。与之形成显著对比的是，焦谷氨酸 - 谷氨酰胺 - 脯氨酰胺（谷氨酰胺 - FPP）在50 - 100 nM添加到未获能的悬浮液中时无生物活性，但能显著抑制FPP在体外对获能和受精能力的刺激作用。此外，当将谷氨酰胺 - FPP + FPP添加到获能的悬浮液中时，谷氨酰胺 - FPP可阻止FPP对自发顶体反应丧失的抑制作用。我们最近的研究表明，FPP和腺苷可引发相似的反应，但似乎作用于不同位点。谷氨酰胺 - FPP抑制对FPP的反应，但不抑制对腺苷的反应，这一事实表明谷氨酰胺 - FPP作用于FPP特异性位点。因此，我们得出结论，FPP分子的特定结构对其生物活性至关重要。去除末端酰胺基团会消除生物活性，并改变中心氨基酸可能会产生显著的功能后果。由于谷氨酰胺 - FPP是FPP生物合成途径中的候选中间肽，且已在人类精液中被鉴定出来，前列腺功能异常可能导致谷氨酰胺 - FPP与FPP一起释放，或取而代之。我们的结果表明，精浆中FPP和相关肽的相对比例可能对体内生育能力产生显著影响。
