蛋白质组学技术在精子蛋白研究中的应用

从蛋白质组学研究的技术手段、蛋白质组学在人类不育及精卵相互识别并结合的机理研究、免疫法开展男性避孕方法的研究及蛋白质组学研究方法在家畜繁殖环节中的应用等几个方面阐述了蛋白质组学在人类生殖及动物繁殖环节相关研究中的重要作用。说明蛋白质组学已经成为生命科学未来发展的主要分支之一,为揭示生命个体的蛋白质动态变化提供了技术手段和理论基础,并将在药物开发,生命活动机理研究等方面发挥巨大作用,也必将会在家畜繁殖学领域发挥其应有的作用。     

二维电泳分离牛精子蛋白的技术研究

二维电泳是蛋白质分离技术并可由于对精子蛋白的分离。本研究旨在通过对双向电泳条件的研究摸索出一种适用于分离牛精子蛋白的二维电泳技术,并利用其对牛精子蛋白进行分离鉴定。在实验中,优化了等电聚焦程序,研究了精子蛋白的不同制备方法、不同上样量、不同胶条长度对电泳结果的影响。结果表明,采用尿素－盐酸胍两步裂解法裂解精子细胞制备蛋白,使用13cm非线性胶条进行蛋白二维电泳,能获得较好的电泳图谱。图谱经二维电泳软件分析,可检测出约800多个蛋白质点,分子量基本分布在10~100KD、等电点约为4~9的区域内。对精子蛋白二维电泳条件的摸索,为后续牛精子X、Y差异蛋白的检测和分析奠定了理论基础。     

高畸形率水牛精子与正常水牛精子差异表达蛋白的分离和鉴定

旨在分析高畸形率和正常水牛精子的差异表达蛋白.运用双向凝胶电泳以及基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS/MS)分析鉴定出高畸形率和正常的水牛精子的差异表达蛋白,并对部分蛋白进行生物信息学分析.结果显示,高畸形率和正常水牛精子之间存在16个表达差异明显的蛋白点,与正常水牛精子相比,5个蛋白斑点表达量上调,6个蛋白斑点下调,3个蛋白斑点缺失,2个蛋白斑点在畸形率高的水牛精子特有.质谱鉴定16个差异蛋白,成功鉴定出6个差异蛋白斑点,对应4种蛋白:左旋天冬酰胺酶、热应激蛋白β-9、半乳糖激酶、β-微管蛋白-2C.研究表明,高畸形率和正常水牛精子蛋白质表达存在一定的差异.     

甘油浓度对蓝狐精子深低温冷冻保存的影响及冻融前后精子的超微结构

人工采取8只优质芬兰雄性蓝狐的精液,分别利用2％、4％、6％和8％甘油浓度的卵黄-Tris-果糖-柠檬酸钠稀释液进行稀释,制成细管冻精。在冻融后0、O．5、2、4、6h检测4种浓度组的精子运动度、质膜完整率、顶体完整率;并利用透射电镜观察冻融前后精子的超微结构变化。冻融后0h,4％甘油浓度组冻融精子的运动度、质膜完整率、顶体的完整率均最高(分别为41．8％、43．6％、48．4％),2％浓度组最低(分别为24．5％、27．6％、31．7％);随着检测时间延长,2％与4％组的精子特性差异显著,但2％、6％、8％3个组间差异不显著;6h时各组间精子的运动度均不超过10％,最高质膜完整率和顶体完整率分别为11．8％、12．7％。说明蓝狐精液稀释剂中甘油的适宜浓度应为4％,冻融后精子的活力维持时间较短。蓝狐精子冻融过程中质膜极易发生膨胀或断裂、顶体囊泡化或溃散,而质膜和顶体丢失现象较少。     

获能期间精子蛋白的酪氨酸磷酸化

哺乳动物精了获能是精子与卵子成功受精的前提。蛋白酪氨酸磷酸化对精子获能十分重要。精了获能期蛋白酪氨酸磷酸化程度增高与sAC/cAMP/PKA途径、受体酪氨酸激酶途径和非受体蛋白酪氨酸激酶途径调节有关。获能过程中酪氨酸磷酸化蛋白分布于精子细胞的不同区域,蛋白的酪氨酸磷酸化与精子功能密切相关。     

重组人睾丸精子结合蛋白对人精子蛋白激酶A及蛋白激酶C活性的影响

为探讨人睾丸精子结合蛋白(human testis sperm binding protein,hTSBP)促进人精子获能的分子机制,检测了重组hTSBP对人精子蛋白激酶A(PICA)和蛋白激酶C(PKC)活性的影响.用重组载体pcDNA3.1/myc-His(-)B-tsbp转染真核细胞后,金属亲和层析纯化表达的重组蛋白质His6-TSBP;重组蛋白质处理健康成人精子后,分别提取精子胞浆及胞膜蛋白组分,发现重组蛋白质可以与精子胞膜结合;经放射自显影检测,发现0.1 mg/ml重组蛋白质可以提高人精子中PKA的活性,对精子膜PKC活性无显著影响.     

少弱精子症患者精子候选差异蛋白Trx 2、TrxR 1的验证及在少精、弱精子症中的表达研究

目的:根据TMT技术筛选少弱精子症患者精子差异蛋白的结果,选取硫氧还蛋白2(thioredoxin 2,Trx 2)、硫氧还蛋白还原酶1(thioredoxin reductase 1,TrxR 1)进行验证,探讨二者在少精、弱精和少弱精子症中的表达变化及其意义。方法:收集105例少精子症组(O组)、150例弱精子症组(A组)、50例少弱精子症组(OA组)和106例正常精液男性(N组)精液,分离出精子,对少弱精子症进行串联质谱标签(Tandem Mass Tag,TMT)技术蛋白质组学分析,根据少弱精子症组的精子差异蛋白结果选取Trx 2、TrxR 1,通过免疫荧光和免疫印迹方法检测其在O组、A组、OA组的表达情况。结果:TMT技术蛋白质组学结果显示Trx 2为上调差异蛋白(为N组的1.31倍),TrxR 1为下调差异蛋白(为N组的0.82倍)。免疫荧光和免疫印迹结果显示O组、A组、OA组Trx 2表达显著高于N组(P0.05),O组、OA组TrxR 1的表达显著低于N组(P0.05)。二者在OA组的结果与蛋白质组学结果一致。结论:Trx 2、TrxR 1可能在少精、弱精及少弱精子症的发生中起着重要的作用,并有望成为少弱精子症患者精子的候选标志物及治疗靶点。     

精子头后部质膜融合蛋白fertilin的研究进展

精子头后部(或赤道区)表面fertilin糖蛋白由相关的两个跨膜亚基α和β构成异二体形式。这两个亚基前体均含有金属蛋白酶区(met-alloprotease domain)和整联蛋白配体区(disin-tegrin domain),属于ADAMs gene家族。α和β前体分别在睾丸和附睾中从上述两区域连接处水解后,得到成熟型亚基。受精时,穿过透明带的顶体反应后精子借助β亚基的disintegrin肽段与卵母细胞表面的整联蛋白结合,同时fertilin结构发生变化,暴露出α亚基上潜在的融合肽段(90—111aa),并介导精子与卵母细胞发生质膜融合,最终完成受精过程。     

棉花种子活力劣变的差异蛋白质组学研究

该研究以新疆本地审定且大面积推广应用的陆地棉品种‘新陆早33’、‘新陆早36’、‘新陆早50’种子为研究材料,采用高温高湿(40℃,RH100%)人工老化方法获得不同活力种子,双向电泳分离‘新陆早50’活力劣变种子总蛋白并对差异蛋白点进行二级质谱(MALDI-TOF/TOF)鉴定分析,以明确棉花种子活力劣变过程中蛋白质组表达的变化,探讨棉花种子老化的分子机制。结果显示:(1)经人工老化获得不同活力水平的种子,经生活力检测发现‘新陆早50’的种子活力随老化时间的延长呈线性下降,可作为蛋白质组研究材料。(2)TCA-丙酮法分别提取‘新陆早50’对照和劣变种子的总蛋白,经2-DE分离,获得了分辨率和重复性较好的蛋白质组差异表达图谱,在等电点4~7、分子量14.4~97.4kD之间发现约350个肉眼可辨的蛋白点,其中上调2倍以上且达到99%统计学显著水平的差异表达蛋白点30个。(3)二级质谱分析发现,有29个蛋白点被成功鉴定,生物信息学分析和功能分类结果表明,与贮藏相关的蛋白有13个,免疫相关蛋白2个,脂代谢相关蛋白1个,能量代谢相关蛋白1个,肌动蛋白2个,功能未知蛋白5个,调控相关蛋白2个,次级代谢物1个,细胞修复防御相关蛋白1个,分泌性蛋白1个。研究认为,分离鉴定的29个差异蛋白的变化可能与棉花种子活力劣变有关。     

Separation of bovine spermatozoa proteins using 2D-PAGE revealed the relationship between tektin-4 expression patterns and spermatozoa motility

Poor semen quality has long been associated with bull infertility. However, the molecular basis in spermatozoa cells underlying the mechanisms of bull infertility remain unknown. The purpose of this study was to determine whether there is any protein in bovine spermatozoa related to semen quality. Semen samples from 18 Brahman bulls, 3 to 10 yrs of age, were assessed for semen quality in terms of spermatozoa motility and spermatozoa morphology. Spermatozoa extracts were separated using 2D-PAGE followed by staining with Coomassie blue. At least one duplicate gel was performed for each sample. Each gel was scanned with an ImageScanner System and analyzed for spots by ImageMaster 2D platinum software. The related protein spot(s) with semen quality was cut from the gel and identified by LC MS/MS. The results showed that at least 600 protein spots were detected in the spermatozoa extracts of the Brahman bulls. Of all these spots, there were 3 of 56 kDa at pI 6.4, 6.6 and 6.8 (Z₁, Z₂ and Z₃, respectively) that clearly showed different expression pattern among 18 Brahman bulls. Of 18 bulls (a) five showed the presence of spot Z₁ and Z₂ (pattern A) (b) one of spot Z₃ (pattern B) (c) five of spot Z₂ and Z₃ (pattern C) (d) one of spot Z₁ (pattern D) and (e) six of spot Z₂ (pattern E). Identification of spot Z₁, Z₂ and Z₃ by LC MS/MS had a similar result as matched to the tektin-4 protein of Bos taurus with a respective score of 171, 557 and 591. The statistical analysis of the 56 kDa protein patterns, tektin-4, indicated a significant effect on spermatozoa motility (P < 0.05) albeit non-significant on spermatozoa morphology. The bulls which showed pattern A had a higher percentage of spermatozoa motility than pattern E (P < 0.05) and not different from pattern C (P > 0.05). The statistical analysis also revealed that the presence of spot Z₁ had an effect on the percentage of spermatozoa motility (P < 0.01), whereas the presence of spot Z₂ and Z₃ had no effect (P > 0.05). The correlation coefficient between the relative protein content of spot Z₁ and the percentage of spermatozoa motility was 0.49. Our study demonstrates that the expression patterns of tektin-4 were a proxy for an effect on spermatozoa motility and consequently bull infertility. It may be that these protein patterns can be used as markers for improving bovine reproduction.     

Distribution of calmodulin and calmodulin-binding proteins in membranes from bovine epididymal spermatozoa

Reproducible concentrations of calmodulin representing approximately 0.1% of the membrane protein were detected in purified plasma membranes from bovine epididymal spermatozoa. When membranes were isolated in the presence of 1 mM EGTA, the amount of calmodulin associated with the plasma membranes was not reduced. Calmodulin-binding proteins were detected in both purified plasma membranes and in a mixed membrane fraction containing both plasma membranes and cytoplasmic droplet membranes. A calcium-dependent, calmodulin-binding protein of apparent molecular weight 123,000 was detected in both fractions. In the presence of 1 mM EDTA, putative calcium-independent calmodulin-binding proteins of apparent molecular weights 93,000, 32,000, 18,000, and 15,000 were detected in the plasma membrane fraction. The 15,000 Mr polypeptide was also present in the mixed membrane fraction but the three proteins of higher molecular weight were reduced or absent in this fraction.     

Effect of prostatic fluid on the quality of fresh and frozen-thawed canine epididymal spermatozoa

Canine epididymal spermatozoa have a low freeze-tolerance ability compared with ejaculated spermatozoa, which could arise from the absence of prostatic fluid (PF). Therefore, the purpose of this work was to elucidate the influence of PF on the quality of canine epididymal sperm before and after freezing. Caudae epididymides were retrieved from eight dogs after routine castration. Spermatozoa were released by slicing the tissue and were extended in either Tris solution or PF before freezing. Frozen sperm samples were thawed at 70 °C for 8 seconds in a waterbath. Sperm concentration, motility using computer-assisted sperm analysis, morphology, plasma membrane, acrosome and chromatin integrity were assessed in the fresh sperm samples (after 20 minutes incubation) and at 0 and 4 hours after thawing. Progressive motility, distance straight line, distance average path, average path velocity, curvilinear velocity, straight line velocity, straightness, linearity, wobble, and beat cross frequency were significantly increased after extraction into PF. There was a higher proportion of spermatozoa with DNA damage in the PF treatment group at 4 hours after thawing than in the Tris treatment group (15.8% vs. 6.7%, P < 0.05). These results suggest that the addition of PF to canine spermatozoa activates sperm motility in fresh spermatozoa but has a negative effect on chromatin integrity after freezing–thawing.     

Temporal synthesis of mitochondrial proteins from mouse epididymal spermatozoa

Mitochondria from ejaculated bovine spermatozoa contain a group of polypeptides ranging in molecular weights from 13,000 to 35,000 not found in other bovine or murine testicular mitochondria [Hecht and Bradley, 1981]. These proteins are present in the mitochondria isolated from both epididymal and ejaculated spermatozoa. To establish when during epididymal transport, spermiogenesis, and/or meiosis these proteins are synthesized, the synthesis intervals for the mitochondrial proteins from cauda epididymal spermatozoa were established following intratesticular injection of (³⁵S)methionine. Mice were killed every third day over a 33-day period and cauda epididymal spermatozoa were fractionated into mitochondrial and head components. Radioactivity in each fraction was monitored by liquid scintillation counting. Maximal incorporation was observed during spermiogenesis, although substantial amounts of protein were synthesized during meiosis. Analysis of the mitochondrial polypeptides by gel electrophoresis revealed that many polypeptides such as the cysteine-rich structural protein of the mitochondrial capsule were synthesized over prolonged intervals of spermiogenesis and meiosis rather than in a brief specific time period. These results suggest that spermatozoal mitochondria are produced by a sequential substitution of new proteins into the differentiating mitochondria rather than the abrupt appearance of a new class of mitochondria during spermatogenesis.     

Cell surface changes in the proteins of rabbit spermatozoa during epididymal passage

Differences in the exposure of spermatozoa surface components during epididymal passage have been examined using lactoperoxidase-catalyzed ¹²⁵I-iodination or labeling with ¹²⁵I-diazodiiodosulfanilic acid. Labeled surface proteins obtained from caput and cauda epididymides were solubilized in detergent, separated by sodium dodecylsulfate polyacrylamide slab gel electrophoresis, and identified by radiography. Densitometer scans of autoradiograms revealed increased amounts or exposures of surface proteins of ～35,000, ～39,000, ～50,000, and ～78,000 molecular weight on the cauda epididymal spermatozoa.     

Study on the role of calmodulin in sperm function through the enrichment and identification of calmodulin-binding proteins in bovine ejaculated spermatozoa

Calmodulin is a small, highly conserved acidic protein present at high levels in spermatozoa that mediates numerous intracellular Ca²⁺-dependent events. Sperm motility and fertilizing ability results from an array of biochemical pathways under Ca²⁺ control, in which the importance of calmodulin is not fully understood. The role of calmodulin in sperm function has been mostly assessed using antagonists. Nevertheless, few known calmodulin-regulated enzymes have been described in spermatozoa regarding their involvement in sperm function. To further understand the role of this important Ca²⁺ mediator in spermatozoa, different studies were also undertaken to investigate and to identify sperm calmodulin-binding proteins and determine their localization and subcellular distribution as an attempt to elucidate the role of this important Ca²⁺ mediator. In the present study, sperm calmodulin-binding proteins were identified by mass spectrometry after Ca²⁺-dependent biotinylated-calmodulin binding on sperm head proteins subjected to 2D electrophoresis and transferred on a polyvinylidene difluoride membrane. Calmodulin binding protein identification was also done on detergent extracted whole sperm proteins pulled down in a Ca²⁺-dependent manner by calmodulin-conjugated sepharose beads. In this latter group, 300 proteins were identified in at least two experiments out of three, and those identified in the three independent experiments were analyzed for overrepresented biological processes using the Bos taurus Gene Ontology database. Proteins with known function in reproductive processes, fertilization, sperm-egg recognition, sperm binding to the zona pellucida, regulation of sperm capacitation, and sperm motility were identified and further emphasize the importance of calmodulin in sperm function.     

Capacitation status of fresh and frozen-thawed buffalo spermatozoa in relation to cholesterol level, membrane fluidity and intracellular calcium

The present study was conducted to assess the capacitation status of fresh and frozen-thawed buffalo spermatozoa and its relationship with sperm cholesterol level, membrane fluidity and intracellular calcium. Semen from seven buffalo bulls (eight ejaculates each) was divided into two parts. Part I was used as fresh semen and part II was extended in Tris–egg yolk extender, equilibrated (4 °C for 4 h) and frozen at −196 °C in LN₂. The fresh and frozen-thawed spermatozoa were assessed for capacitation status using chlortetracycline (CTC) fluorescent assay, membrane fluidity using merocyanine 540/Yo-Pro-1 assay and intracellular calcium using Fluo-3 AM with flowcytometry. Results revealed a significant (P < 0.01) increase in capacitated sperm population in frozen-thawed semen compared to fresh semen (42.21% vs 14.32%). Similarly, a significantly (P < 0.01) higher proportion of frozen-thawed live spermatozoa showed high membrane fluidity (53.62% vs 25.67%) and high intracellular calcium (43.68% vs 11.72%) compared to fresh semen. The sperm cholesterol was significantly (P < 0.01) reduced after freezing–thawing as compared to fresh semen. The proportion of capacitated spermatozoa (CTC pattern B) was positively correlated with the proportion of sperm with high intracellular calcium (r = 0.81) and high membrane fluidity (r = 0.65), and negatively correlated with cholesterol level (r = −0.56) in frozen-thawed semen. The membrane fluidity was also strongly associated with the cholesterol level and intracellular calcium. The study concluded that changes in buffalo spermatozoa and established the relationship among capacitation status, sperm cholesterol level, membrane fluidity and intracellular calcium concentration in frozen-thawed spermatozoa.     

Selective binding of specific rat epididymal secretory proteins to spermatozoa and erythrocytes

Tissue pieces from the caput epididymidis of the rat were incubated in vitro with (³⁵S) methionine to produce radioactive secretory proteins. The radioactive secretory proteins so formed were tested for their ability to bind to washed rat spermatozoa collected from the rete testis and cauda epididymidis, and to rat erythrocytes. The sperm and erythrocytes bound approximately 5% of the total radioactive protein. Binding was protein-specific in that only selected proteins became associated with the cells. Binding was not cell-specific, however, since testicular spermatozoa, caudal spermatozoa, and erythrocytes all bound the same proteins to a similar degree.     

Silver staining analysis on spermatozoa of Nucella lapillus (Gastropoda,Prosobranchia)

Summary

Sperm of Nucella lapillus was studied by electron microscopy, including the application of a cytochemical silver method. Using silver impregnation a dense precipitation of Ag granules in spermatocyte II nucleoli was seen over the fibrillar component and a slight one in the granular component. On longitudinal sections of the spermatozoon the results demonstrate that argyrophilic proteins are located in the external limiting zone of the acrosome in the anterior portion of the nucleus between the cytoplasmic and the nuclear membranes, in the posterior end of the nucleus and in the terminal portion of the middle region. These data indicate an affinity for silver in areas of the cytoplasm containing microtubules and in zones of transition.     

Intracellular signaling cascades induced by relaxin in the stimulation of capacitation and acrosome reaction in fresh and frozen-thawed bovine spermatozoa

Relaxin is one of the 6-kDa peptide hormones, which acts as a pleiotropic endocrine and paracrine factor. Our previous studies revealed that sperm capacitating medium containing relaxin induced capacitation and acrosome reaction (AR) in fresh and frozen-thawed porcine or bovine spermatozoa. However, the intracellular signaling cascades involved with capacitation or AR induced by relaxin was unknown. Therefore, the present study was designed to investigate the intracellular signaling cascades involved with capacitation and AR induced by relaxin in fresh and frozen-thawed bovine spermatozoa. Spermatozoa were incubated in sperm Tyrode's albumin lactate pyruvate (Sp-TALP) medium supplemented with (40 ng ml(-1)) or without relaxin, and subjected to evaluation of chlortetracycline staining pattern, cholesterol efflux, Ca(2+)-influx, intracellular cyclic adenosine monophosphate (cAMP) and protein tyrosine phosphorylation. Capacitation and AR were increased (P<0.05) in both fresh and frozen-thawed spermatozoa incubated with relaxin. Cholesterol effluxes were greater in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa incubated with relaxin than the spermatozoa incubated without relaxin. Ca(2+)-influxes were also significantly stimulated by relaxin in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa. The Sp-TALP medium containing relaxin influenced the generation of intracellular cAMP in the fresh (P<0.01) and frozen-thawed (P<0.05) spermatozoa, and exhibited higher exposure of protein tyrosine phosphorylation in both sperm types than the medium devoid of relaxin. Therefore, the results postulate that relaxin exerts the intracellular signaling cascades involved with capacitation and AR through accelerating the cholesterol efflux, Ca(2+)-influx, intracellular cAMP and protein tyrosine phosphorylation in fresh and frozen-thawed bovine spermatozoa.