斯钙素在哺乳动物骨组织代谢中的作用

斯钙素（stanniocalcin,STC）是一种最早在硬骨鱼中发现的糖蛋白类激素. 哺乳动物斯钙素在体内钙磷代谢、肌肉骨骼系统的发育等方面均起到重要作用,并且在心血管疾病、肿瘤发展以及神经系统疾病中也扮演重要角色. 近年,斯钙素在骨骼发育中的作用逐渐引起科学界的关注. 骨组织中STC由成软骨细胞、成骨细胞分泌,并以自分泌/旁分泌的形式作用于局部组织细胞中,主要影响软骨形成和骨重建过程.本文以斯钙素为主题,综述了其生化分子特性、其在骨组织中的表达分布特点,以及该分子在成熟骨组织骨重建过程中的作用机制. 本文将为深入了解斯钙素在骨组织代谢中的作用提供帮助.     

中华大蟾蜍斯钙素基因的组织表达及其在肾脏中的细胞定位

斯钙素(Stanniocalcin, STC)是一类首先在鱼类特有的内分泌腺--斯坦尼氏小体(Corpuscles of Stannius, CS)、随后又在人和哺乳动物中发现的同型二聚体糖蛋白激素,具有广泛的组织表达模式和多种生物学效应.为阐明两栖类动物是否存在STC1基因的表达及其表达模式,本研究基于部分已知鱼类和哺乳动物的STC1基因序列,从中华大蟾蜍(Bufo bufo gargarizans)卵巢获得了STC1基因的部分序列(GenBank注册号为EF586886).同源性分析显示,所获得的中华大蟾蜍STC1基因部分序列与鱼类STC1基因相应序列的同源性在40%-48%,而与小鼠和人STC1基因相应序列的同源性分别为41.89%和37.95%.RT-PCR分析显示STC1基因可在肾脏、性腺等多种组织中表达;原位杂交(in situ hybridization, ISH)技术表明中华大蟾蜍肾脏的近端小管、远端小管和集合管细胞内表达STC1 mRNA.这些结果首次证实两栖类动物中华大蟾蜍组织中存在STC1基因的表达     

斯钙素与哺乳动物生殖的研究进展

斯钙素(stanniocalcin,STC)是一类首先在硬骨鱼类发现的糖蛋白激素,其生理作用在于调节钙磷稳态。近年来在入和哺乳动物组织中也发现存在有STC,并且以旁分泌方式参与机体的多种生理功能。本文综述了近年来哺乳动物胚胎发育、妊娠及哺乳期间STC基因在卵巢内的表达,早期胚胎植入过程中STC基因在子宫内膜的表达,以及人绒毛膜促性腺激素(hCG)对STC分泌的调节作用及其作用机制。研究表明,新生个体的STC基因表达首先出现在卵巢的膜细胞内,随后出现于卵巢基质的间质细胞和内膜细胞;但STC基因的表达产物STC却聚积于卵母细胞和黄体细胞内,提示STC参与卵母细胞的成熟过程。胚胎植入、妊娠、分娩与哺乳期间卵巢内STC基因表达量的动态变化行为,提示STC在哺乳动物生殖过程的各个环节均发挥一定的作用。     

STC1在生殖相关肿瘤中的作用与分子机制

斯钙蛋白1(stanniocalcin 1,STC1)是一种调节血浆钙磷平衡的糖蛋白激素。之前STC1的研究多集中于钙磷平衡、氧化应激、炎症反应等过程。近来研究发现，STC1在肿瘤的发生、生长、增殖、凋亡、侵袭转移等过程中发挥了重要作用。本文对STC1在生殖相关肿瘤，如乳腺癌、卵巢癌、宫颈癌、前列腺癌和膀胱癌中的研究进展进行综述，总结了STC1在不同肿瘤中的表达、作用机制以及与肿瘤预后的关系，旨在为肿瘤治疗提供新思路。     

皮肤烫伤修复期斯钙素-1基因表达与组织过氧化氢水平变化

目的：检测皮肤烫伤修复期斯钙素-1（STC1）基因表达与组织过氧化氢（H202）水平的变化。方法：在小鼠Ⅱ度烫伤模型上,采用生物化学和RT-PCR方法检测损伤部位组织H2O2含量及STC1 mRNA水平。结果：组织H2O2水平在皮肤烫伤后12h升高,略微下降后继续升高,至烫伤后120h达到最高值;而STC1 mRNA水平始终处于较高水平,分别在烫伤后12h和120h各出现一次高峰。结论：皮肤烫伤修复期组织STC1 mRNA水平与组织H2O2水平变化具有相关性。     

一组玉米胚钙沉淀蛋白的初步研究

从玉米胚中分离出一组理化性质相似的可为钙所沉淀的蛋白。该组蛋白可被3％的三氯乙酸和55％的硫酸铵可逆沉淀,具有较高的热稳定性,在93～94℃下5min不沉淀。该组钙沉淀蛋白可被等于或大于1mmol／L的CaCl2可逆地沉淀,但不被MgCl2或NaCl沉淀。该组蛋白在EGTA存在下可与phenyl－sepharose4B结合而被含Ca2 的缓冲液所洗脱。它们由7种蛋白质组成,亚基分子量为16～103kD。它们的一些理化性质类似于从动物肌肉细胞中提取的钙结合蛋白calsequestrin,其功能可能与缓冲和调节细胞游离Ca2 水平有关。     

在斯钙素的研究进展

本文概述了近年来有关硬骨鱼类斯坦尼氏小体分泌激素－－斯钙素的研究进展。ＳＴＣ是糖蛋白类激素,为同型二聚全,其表观分子量在天然状态下从４６（大麻哈鱼）－５６（虹鳟）ｋＤａ,还原状态下则为２３－２８ｋＤａ,ＳＴＣ单体的氨基序列分析表明,大麻哈鱼、银大麻便和澳大利亚鳗鲡的氨基酸残基数分别为１７９、２２３和２３１个。研究还表明,ＳＴＣ的分泌受血钙浓度的晴天有神经参与ＳＴＣ的释放。     

胶原酶—3活性在大鼠动情周期及胚泡着床中的变化

大鼠动情周期以及胚胎着床过程中,子宫内膜会发生结缔组织的降解与重构。胶原酶3（MMP－13）是降解纤维类胶原的主要蛋白水解酶类之一。其活性在这些过程中的变化值得研究。采用液体闪烁计数测定^3H标记胶原的方法,对大鼠动情周期及早期妊娠子宫中胶原酶3（MMP－13）的活性进行了测定。结果表明：在动情周期中,激活型MMP－13在间情期最低,酶原型及激活型的MMP－13在动前期达高峰,动情后期酶原型和激活型MMP也明显高于间情期（P＜0．05）（Fig.1)。妊娠第1、2天酶原型的MMP－13的活性显著高于第3－7天,第3、4天酶原型和激活型MMP－13的活性均低于妊娠第1、2天（P＜0．05）;而第5天酶原型MMP－13的活性却显著高于第4、6两天（P＜0．05）,激活型MMP－13的活性也高于第4天（P＜0．05）（Fig.2）。着床部位酶原型MMP－13的活性明显高于非着床部位（P＜0．05）,而激活型MMP－13的活性则无明显差异（P＞0．05）（Fig.3）。大鼠假孕早期子宫中MMP－13的活性变化与正常早期妊娠相似,但其活性却明显低于正常早期妊娠（Fig.4）。结果提示:粝鼠子宫中MMP－13参与大鼠动情周期及早期妊娠过程,尤其是在胚胎着床过程中可能起着重要作用。     

钙蛋白酶对兔脑皮质中细胞骨架蛋白tau的降解作用

钙蛋白酶 (calpain)是钙依赖性中性蛋白酶 ,根据其对钙敏感性的不同 ,可分为m 和 μ 钙蛋白酶两型。分别用不同浓度CaCl2 溶液温育Wistar大鼠脑皮质匀浆液 ,并用Western印迹和定量图像分析技术检测不同亚型钙蛋白酶对tau蛋白的降解作用。发现 :在 37℃用 1mmol LCa2 温育底物 15min ,即出现大量分子量为 2 9kD的tau蛋白降解片段 ;当Ca2 浓度为 5mmol L时 ,tau蛋白几乎全部被降解 ;这种tau蛋白降解可被特异性的钙蛋白酶抑制剂完全逆转。进一步的研究发现 ,分别用 μ 钙蛋白酶抑制剂 ( 0 .0 5 μmol Lcalpastatin) ,m 钙蛋白酶抑制剂 ( 10 0 μmol LcalpaininhibitorIV)或总钙蛋白酶抑制剂 ( 5 5 2 μmol Lcalpeptin)与 1mmol LCa2 共同温育Wistar大鼠脑皮质匀浆液 ,1mmol LCa2 激活的tau蛋白降解分别被抑制 8.6 %、92 .5 %和 97.8%。该研究结果表明 ,一定浓度的Ca2 可同时激活 μ 钙蛋白酶和m 钙蛋白酶 ,这两种亚型均参与降解tau蛋白 ,但m 钙蛋白酶的作用比 μ 钙蛋白酶更强     

前列腺素F（PGF）抗血清对小鼠胚泡着床的影响

本文试图利用自制的PGP抗血清,对小鼠子宫局部进行注射,以观察其对胚泡着床的影响。结果表明,于妊娠第3天(孕卵在输卵管阶段)单侧子宫角注射PGF抗血清,对胚泡着床无影响。而妊娠第4天(胚泡在子宫阶段〕单侧或双侧子宫角注射PGF抗血清,对胚泡着床均有明显的抑制作用。这一结果提示小鼠胚泡着床中PGF起着重要的作用。     

Stanniocalcin 2: characterization of the protein and its localization to human pancreatic alpha cells.

Stanniocalcin (STC) is a hormone that was originally identified in fish, where it inhibits calcium uptake by the gills and gut and stimulates phosphate adsorption by the kidney. Recently, two mammalian homologues of stanniocalcin were identified. The first (STC1) shows 61% identity to the fish stanniocalcins and appears to have a function similar to that of the fish stanniocalcins. The second homologue (STC2) is 30-38% identical to the fish stanniocalcins, and is characterized by unique cysteine and histidine motifs that are not found in the other stanniocalcins. We purified both the native hamster and recombinant human STC2 proteins and obtained a partial amino acid sequence of the hamster protein. Both proteins behave as a disulfide bonded homodimer, which undergoes post-translational modification(s). The STC2 gene was localized to human chromosome 5q35. Northern blot analysis revealed that the primary site of human STC2 production is the pancreas, and immunostaining localized the STC2 protein to a subpopulation of cells in the islet. Double immunostaining for STC2 and either insulin or glucagon revealed that STC2 protein is found in the alpha cells, but not the beta cells. We speculate that STC2 may play a role in glucose homeostasis.     

Genomics reveal ancient forms of stanniocalcin in amphioxus and tunicate

Stanniocalcin (STC) is present throughout vertebrates, including humans, but a structure for STC has not been identified in animals that evolved before bony fish. The origin of this pleiotropic hormone known to regulate calcium is not clear. In the present study, we have cloned three stanniocalcins from two invertebrates, the tunicate Ciona intestinalis and the amphioxus Branchiostoma floridae. Both species are protochordates with the tunicates as the closest living relatives to vertebrates. Amphioxus are basal to both tunicates and vertebrates. The genes and predicted proteins of tunicate and amphioxus share several key structural features found in all previously described homologs. Both the invertebrate and vertebrate genes have four conserved exons. The predicted length of the single pro-STC in Ciona is 237 amino acids and the two pro-hormones in amphioxus are 207 and 210 residues, which is shorter than human pro-STCs at 247 and 302 residues due to expansion of the C-terminal region in vertebrate forms. The conserved pattern of 10 cysteines in all chordate STCs is crucial for identification as amphioxus and tunicate amino acids are only 14-23% identical with human STC1 and STC2. The 11th cysteine, which is the cysteine shown to form a homodimer in vertebrates, is present only in amphioxus STCa, but not in amphioxus STCb or tunicate STC, suggesting the latter two are monomers. The expression of stanniocalcin in Ciona is widespread as shown by RT-PCR and by quantitative PCR. The latter method shows that the highest amount of STC mRNA is in the heart with lower amounts in the neural complex, branchial basket, and endostyle. A widespread distribution is present also in mammals and fish for both STC1 and STC2. Stanniocalcin is a presumptive regulator of calcium in both Ciona and amphioxus, although the structure of a STC receptor remains to be identified in any organism. Our data suggest that amphioxus STCa is most similar to the common ancestor of vertebrate STCs because it has an 11th cysteine necessary for dimerization, an N-glycosylation motif, although not the canonical one in vertebrate STCs, and similar gene organization. Tunicate and amphioxus STCs are more similar in structure to vertebrate STC1 than to vertebrate STC2. The unique features of STC2, including 14 instead of 11 cysteines and a cluster of histidines in the C-terminal region, appear to be found exclusively in vertebrates.     

Identification of Ran-binding protein M as a stanniocalcin 2 interacting protein and implications for androgen receptor activity

Stanniocalcin (STC), a glycoprotein hormone originally discovered in fish, has been implicated in calcium and phosphate homeostasis. While fishes and mammals possess two STC homologs (STC1 and STC2), the physiological roles of STC2 are largely unknown compared with those of STC1. In this study, we identified Ran-binding protein M (RanBPM) as a novel binding partner of STC2 using yeast two-hybrid screening. The interaction between STC2 and RanBPM was confirmed in mammalian cells by immunoprecipitation. STC2 enhanced the RanBPM-mediated transactivation of liganded androgen receptor (AR), but not thyroid receptor β, glucocorticoid receptor, or estrogen receptor β. We also found that AR interacted with RanBPM in both the absence and presence of testosterone (T). Furthermore, we discovered that STC2 recruits RanBPM/AR complex in T-dependent manner. Taken together, our findings suggest that STC2 is a novel RanBPM-interacting protein that promotes AR transactivation. [BMB Reports 2014; 47(11): 643-648]     

Effect of 710 nm visible light irradiation on neurite outgrowth in primary rat cortical neurons following ischemic insult

Stanniocalcin 2 (STC2) is a homolog of stanniocalcin 1, a 56kD glycoprotein hormone that originally was found to confer calcitonin-like activity in fish. Human STC2 is expressed in various tissues such as kidney, spleen, heart, and pancreas. STC2 has been demonstrated to be induced by different kinds of stress and display cytoprotective activity, but the molecular mechanism is poorly understood. Heme oxygenase 1 (HO1) degrades heme to biliverdin, carbon monoxide and free iron, and is a stress-responsive protein. Using yeast two-hybrid screening we identified HO1 as a binding partner of STC2. The interaction was validated by in vivo co-immunoprecipitation and immunofluorescence. The binding site for HO1 was located to amino acids 181-200 of STC2. We also found that STC2 binds hemin via a consensus heme regulatory motif. Moreover, STC2 expression was induced by heat shock in HEK293 cells. Taken together, our findings point to three novel functions of STC2, and suggest that STC2 interacts with HO1 to form a eukaryotic 'stressosome' involved in the degradation of heme.     

Stanniocalcin 2 is a negative modulator of store-operated calcium entry

The regulation of cellular Ca(2+) homeostasis is essential for innumerable physiological and pathological processes. Stanniocalcin 1, a secreted glycoprotein hormone originally described in fish, is a well-established endocrine regulator of gill Ca(2+) uptake during hypercalcemia. While there are two mammalian Stanniocalcin homologs (STC1 and STC2), their precise molecular functions remain unknown. Notably, STC2 is a prosurvival component of the unfolded protein response. Here, we demonstrate a cell-intrinsic role for STC2 in the regulation of store-operated Ca(2+) entry (SOCE). Fibroblasts cultured from Stc2 knockout mice accumulate higher levels of cytosolic Ca(2+) following endoplasmic reticulum (ER) Ca(2+) store depletion, specifically due to an increase in extracellular Ca(2+) influx through store-operated Ca(2+) channels (SOC). The knockdown of STC2 expression in a hippocampal cell line also potentiates SOCE, and the overexpression of STC2 attenuates SOCE. Moreover, STC2 interacts with the ER Ca(2+) sensor STIM1, which activates SOCs following ER store depletion. These results define a novel molecular function for STC2 as a negative modulator of SOCE and provide the first direct evidence for the regulation of Ca(2+) homeostasis by mammalian STC2. Furthermore, our findings implicate the modulation of SOCE through STC2 expression as one of the prosurvival measures of the unfolded protein response.     

Contrasting effects of stanniocalcin-related polypeptides on macrophage foam cell formation and vascular smooth muscle cell migration

Stanniocalcin (STC) is a calcium- and phosphate-regulating hormone secreted by the corpuscles of Stannius, an endocrine gland of bony fish. Its human homologues, STC1 and STC2 showing 34% amino acid identity each other, are expressed in a variety of human tissues. To clarify their roles in atherosclerosis, we investigated the effects of their full-length proteins, STC1(18–247) and STC2(25–302), and STC2-derived fragment peptides, STC2(80–100) and STC2(85–99), on inflammatory responses in human umbilical vein endothelial cells (HUVECs), human macrophage foam cell formation, the migration and proliferation of human aortic smooth muscle cells (HASMCs) and the extracellular matrix expression. All these polypeptides suppressed lipopolysaccharide-induced expressions of interleukin-6, monocyte chemotactic protein-1, and intercellular adhesion molecule-1 in HUVECs. Oxidized low-density lipoprotein-induced foam cell formation was significantly decreased by STC1(18–247) and increased by STC2(80–100) and STC2(85–99), but not STC2(25–302), in human macrophages. Expression of acyl-CoA:cholesterol acyltransferase-1 (ACAT1) was significantly suppressed by STC1(18–247) but stimulated by STC2(80–100) and STC2(85–99). Expression of ATP-binding cassette transporter A1 was significantly stimulated by STC1(18–247). Neither STC1(18–247) nor STC2-derived peptides significantly affected CD36 expression in human macrophages or HASMC proliferation. STC2(80–100) and STC2(85–99) significantly increased HASMC migration, whereas STC1(18–247) significantly suppressed the angiotensin II-induced HASMC migration. Expressions of collagen-1, fibronectin, matrix metalloproteinase-2, and elastin were mostly unchanged with the exception of fibronectin up-regulation by STC2(80–100). Our results demonstrated the contrasting effects of STC1 and STC2-derived peptides on human macrophage foam cell formation associated with ACAT1 expression and on HASMC migration. Thus, STC-related polypeptides could serve as a novel therapeutic target for atherosclerosis.     

Stanniocalcin 1 affects redox status of swine granulosa cells

Stanniocalcin 1 (STC1) is a glycoprotein hormone expressed in different mammalian tissues. In previous studies, we showed STC1 expression in swine ovarian follicles and we demonstrated that STC1 may be a physiological regulator of follicular function. Since reactive oxygen species (ROS) are important signal transducers in the ovary, the present study was undertaken to investigate STC1 action on ROS generation and on the activity of the major enzymatic and non-enzymatic scavengers in swine granulosa cells. O(2)- generation, catalase activity and FRAP levels were increased by STC1, whereas H(2)O(2) generation and peroxidase activity were decreased by STC1. Taken together, our data show that STC1 modulates redox status in swine granulosa cells.     

Stanniocalicin 2 Suppresses Breast Cancer Cell Migration and Invasion via the PKC/Claudin-1-Mediated Signaling

Stanniocalcin (STC), a glycoprotein hormone, is expressed in a wide variety of tissues to regulate Ca²⁺ and PO4^- homeostasis. STC2, a member of STC family, has been reported to be associated with tumor development. In this study, we investigated whether the expression of STC2 is associated with migration and invasion of breast cancer cells. We found that breast cancer cell line 231 HM transfected with STC2 shRNA displayed high motility, fibroblast morphology, and enhanced cell migration and invasion. Introduction of STC2 in 231 cells reduced cell migration and invasion. In response to irradiation, silencing of STC2 in 231 HM cells reduced apoptosis, whereas overexpression of STC2 in 231 cells promoted apoptosis, compared with in control cells. Mechanistic study showed that STC2 negatively regulated PKC to control the expression of Claudin-1, which subsequently induced the expressions of EMT-related factors including ZEB1, ZO-1, Slug, Twist, and MMP9. Suppression of PKC activity by using a PKC inhibitor (Go 6983) restored the normal motility of STC2-silenced cells. Furthermore, in vivo animal assay showed that STC2 inhibited tumorigenesis and metastasis of breast cancer cells. Collectively, these results indicate that STC2 may inhibit EMT at least partially through the PKC/Claudin-1-mediated signaling in human breast cancer cells. Thus, STC2 may be exploited as a biomarker for metastasis and targeted therapy in human breast cancer.     

Stanniocalcin 1 as a pleiotropic factor in mammals

Stanniocalcin (STC)1 is the mammalian homologue of STC which was originally identified as a calcium/phosphate-regulating hormone in bony fishes. STC1 is a homodimeric phosphoglycoprotein with few if any identified unique motifs in its structure with the exception of CAG repeats in the 5'-untranslated region. In contrast to fish STC which is expressed mainly in the corpuscles of Stannius, STC1 is expressed in a wide variety of tissues, but unexpectedly is not detected in the circulation under normal circumstances. Thus, STC1 may play an autocrine/paracrine rather than a classic endocrine role in mammals. Consistent with this, pleiotropic effects of STC1 have been postulated in physiological and measured in pathological situations. There is much current interest in identifying a specific STC1 receptor and putative signaling pathways to which it may be coupled. In this regard, STC1 may regulate intracellular calcium and/or phosphate (Pi) levels. In the skeletal system, for example, Pi uptake in bone-forming osteoblasts via a direct effect of STC1 on expression of the NaPi transporter Pit1 may contribute to bone formation. Here we review current understanding of the role of STC1 and its possible molecular mechanisms in the skeleton and elsewhere.