Interactions of pleiotrophin with receptor type protein tyrosine phosphatase

Pleiotroin(PTN)是一种重要的细胞因子，负责刺激细胞分化、神经发育、 血管生成和造血干细胞维持。尽管PTN对术后组织再生至关重要 损伤、细胞因子的错误表达往往会导致致病条件。具体来说，PTN是 在大量癌症中过度表达和PTN活性降低会降低生长速度和 这些癌症的转移潜能。这表明PTN信号可能是一个有价值的靶点来治疗 疾病的数量。然而，人们对PTN信号的结构机制知之甚少。我们想要 研究调节PTN与受体类型蛋白酪氨酸相互作用的结构决定因素 磷酸酶Zeta(PTPRZ)--一种硫酸软骨素蛋白多糖及其受体 有丝分裂和血管生成活性。我们的假设是PTN的两个独立的结构域可以交叉链接 PTPRZ通过与其糖胺多聚糖链或核心蛋白结合，导致PTPRZ自身抑制。我们 想要证实我们的模型，并研究GAG诱导的PTN寡聚体是否在PTN信号转导中是必需的。 在我们的初步研究中，我们已经确定了PTN的结构，并显示了PTN对 糖胺多糖依赖于糖胺多糖的硫酸盐化密度和艾杜糖酸盐含量。我们还展示了 PTN的C-末端尾巴对PTPRZ信号的关键是必不可少的，原因不明 与PTPRZ中发现的CS类型保持稳定的相互作用，并且PTN与 PTPRZ蛋白具有比CS更高的亲和力，从而为PTPRZ提供了额外的机制 交联剂。我们还发现，只有在糖胺聚糖存在的情况下，PTN才会发生齐聚 而PTN齐聚界面很可能涉及PTN中的两个结构域。建立在 随着我们前期研究的成功，我们希望进一步研究PTN信号的结构机制。 具体地说，我们建议：1)确定PTN-Gag络合物的结构，重点是过硫酸盐化 皮肤素硫酸盐，它可能是一种有效的PTN抑制剂。2)确定了PTN的齐聚物结构 并设计PTN的必备单体，以研究PTN低聚物在其与PTPRZ相互作用中的作用。 3)确定PTN与PTPRZ的蛋白质组分相互作用的功能影响，并找到其他 PTPRZ核心蛋白中的PTN结合位点。这些相互作用可能是PTN-PTPRZ的关键部分 因此，如果不考虑这种相互作用，PTN活性的调节是不完整的。4) 用一种新的模型研究PTN的活性是否与其交联蛋白多糖的能力有关 蛋白多糖系统。这个系统将允许我们测试交联性是否依赖于 PTPRZ，并考察了葡聚糖硫酸盐化密度和长度对PTN的交联度和活性的影响。

Pleiotrophin (PTN) is a vital cytokine responsible for stimulating cell differentiation, neural development, angiogenesis and hematopoietic stem cell maintenance. Although PTN is crucial to tissue regeneration after injury, errant expression of the cytokine often leads to pathogenic conditions. Specifically, PTN is overexpressed in a large number of cancers and reduction of PTN activity decreases the growth rates and metastatic potentials of those cancers. This indicates PTN signaling maybe a valuable target for treating a number of ailments. However, little is known about the structural mechanism of PTN signaling. We want to investigate structural determinants that regulate PTN’s interactions with receptor-type protein tyrosine phosphatase zeta (PTPRZ), a chondroitin sulfate (CS) proteoglycan and the receptor associated with PTN’s mitogenic and angiogenic activities. Our hypothesis is that PTN’s two independent domains can cross link PTPRZ by binding to their glycosaminoglycan chains or core proteins, resulting in PTPRZ auto-inhibition. We want to confirm our model and investigate whether GAG-induced PTN oligomer is necessary in PTN signaling. In our preliminary studies, we have determined PTN’s structure and showed PTN’s affinity for glycosaminoglycan is dependent on the sulfation density and iduronate content of the glycan. We also showed that the C-terminal tail of PTN, known to be crucial for PTPRZ signaling for unexplained reasons, is essential to maintaining stable interactions with the type of CS found in PTPRZ, and that PTN binds to a segment of the PTPRZ protein with even higher affinity than CS, thereby providing additional mechanisms for PTPRZ crosslinking. We also showed that PTN oligomerization only happens in the presence of glycosaminoglycans and the PTN oligomerization interface most likely involve both structural domains in PTN. Building on the success of our preliminary studies, we want to further investigate structural mechanisms of PTN signaling. Specifically, we propose to: 1) Determine structures of PTN-GAG complexes with a focus on oversulfated dermatan sulfate, which can potentially be a potent PTN inhibitor. 2) Determine the oligomer structure of PTN and engineer obligatory monomers of PTN to examine the role of PTN oligomers in its interactions with PTPRZ. 3) Determine the functional impact of PTN’s interactions with the protein component of PTPRZ and find other PTN-binding sites in the PTPRZ core protein. These interactions could be a crucial part of PTN-PTPRZ signaling, therefore modulation of PTN activity is not complete without considering such interactions. 4) Investigate whether PTN’s activity is associated with its ability to crosslink proteoglycans using a novel model proteoglycan system. This system will allow us to test whether crosslinking is dependent on the core protein of PTPRZ and investigate the influence of glycan sulfation density and length on crosslinking and activity of PTN.