Functional significance of Siglec-6, a novel leptin receptor, in human placental

描述（由申请人提供）：子痫前期（PE）是一种妊娠特异性疾病，在全世界每年造成50-76,000例孕产妇死亡。美国15%的早产是由PE引起的，占新生儿发病率和死亡率的重要比例。据估计，美国每年因体育锻炼造成的直接医疗保健费用为70亿美元。PE的发病机制被认为始于妊娠前半期，细胞滋养细胞（CTBs）向母体组织的间质和血管内浸润受损。我们最近研究了合并PE的妊娠中胎盘基底板（CTB侵袭区域）的基因表达谱，鉴定了55个PE中与对照组相比差异表达的基因，其中包括40多个新靶点。我们的长期目标是确定这些差异表达基因是否在CTB生物学中发挥关键作用，特别是它们在间质和血管内侵袭中的作用以及它们对PE早期阶段的贡献。在本研究中，我们重点研究了瘦素和Siglec-6（唾液酸结合Ig样凝集素6）这两个差异表达基因在滋养细胞侵袭中的作用。siglece -6最初被克隆为瘦素结合蛋白（OB-BP1），其细胞内尾部含有保守的免疫受体酪氨酸基抑制基序（ITIM）和ITIM样基序，这表明siglece -6具有信号传导潜力。虽然所有被研究的灵长类动物的B淋巴细胞都表达siglece -6，但只有人类胎盘表达siglece -6，这是一个有趣的发现，因为PE是一种依赖于胎盘的人类特异性疾病。有趣的是，典型瘦素受体（ObR）在我们的PE微阵列数据中没有差异表达，这表明siglece -6可能是PE的关键瘦素受体。此外，我们已经确定瘦素可以促进体外CTB侵袭，而siglece -6表达可以消除CTB细胞系中的这种作用。这些观察结果导致了我们的总体假设，即siglece -6的过表达通过作为抑制瘦素受体削弱CTB侵袭在PE发病机制中发挥作用。在本提案中，我们将通过回答以下问题来验证Siglec-6过表达通过改变ObR信号抑制瘦素促进CTB分化和侵袭的假设：siglece -6是否抑制瘦素促进人CTB侵袭？目的2：对人类CTB侵袭至关重要的ObR信号通路是否被Siglec-6表达修饰？目的3：在CTB分化和侵袭过程中，siglece -6表达改变了ObR信号的哪些下游靶点？发现PE相关分子瘦素和Siglec-6如何调节CTB侵袭，将确定它们在PE早期发病机制中的潜在作用。最终，了解调节滋养细胞侵袭的复杂途径将为开发新的预防、诊断和/或治疗策略提供必要的见解，这些策略针对的是这种严重妊娠疾病的原因，而不是后果，从而改善每年受PE困扰的800万对母婴的健康。

DESCRIPTION (provided by applicant): Preeclampsia (PE) is a pregnancy-specific disease that accounts for significant morbidity and 50-76,000 maternal deaths annually worldwide. Fifteen percent of all US preterm births result from PE, accounting for significant neonatal morbidity and mortality. The immediate US health care costs attributable to PE are estimated at $7 billion per year. PE pathogenesis is thought to begin in the first half of pregnancy with impaired interstitial and endovascular invasion of cytotrophoblasts (CTBs) into the maternal tissue. We recently examined the gene expression profile of the placental basal plate, the region of CTB invasion, in pregnancies complicated by PE, identifying 55 genes that are differentially expressed in PE compared to controls including over 40 novel targets. Our long-range goal is to determine whether these differentially expressed genes play key roles in CTB biology, specifically their role in interstitial and endovascular invasion and their contribution to the early stages of PE. For this proposal, we focus the roles of on two of the differentially expressed genes- leptin and Siglec-6 (sialic acid binding Ig like lectin 6) - in trophoblast invasion. Siglec-6 was originally cloned as a leptin binding protein (OB-BP1) with an intracellular tail containing a conserved immunoreceptor tyrosine-based inhibitory motif (ITIM) and an ITIM-like motif, suggesting that Siglec-6 has signaling potential. While the B lymphocytes of all studied primates express Siglec-6, only human placenta expresses Siglec-6, which is intriguing given PE is a human-specific disease dependent upon the placenta. Interestingly, the canonical leptin receptors (ObR) were not differentially expressed in our PE microarray data suggesting that Siglec-6 may serve as the critical leptin receptor in PE. Additionally, we have established that leptin can promote human CTB invasion in vitro and that Siglec-6 expression can abrogate this effect in CTB cell lines. These observations lead to our overall hypothesis that overexpression of Siglec-6 plays a role in PE pathogenesis by functioning as an inhibitory leptin receptor to impair CTB invasion. In this proposal we will test the hypothesis that Siglec-6 overexpression inhibits leptin promotion of CTB differentiation and invasion by altering ObR signaling by answering the following questions: Aim 1. Does Siglec-6 inhibit leptin promotion of human CTB invasion? Aim 2: Are the ObR signaling pathways critical for human CTB invasion modified by Siglec-6 expression? Aim 3: What downstream targets of ObR signaling are altered by Siglec-6 expression during CTB differentiation and invasion? Discovering how the PE-associated molecules leptin and Siglec-6 regulate CTB invasion will determine their potential role in early PE pathogenesis. Ultimately, understanding the complex pathways that regulate trophoblast invasion will provide the insights needed to develop novel preventative, diagnostic and/or treatment strategies geared at the cause rather than the consequences of this serious pregnancy disease, thereby improving the health of the 8 million woman-infant pairs annually afflicted by PE.