Interactions of pleiotrophin with receptor type protein tyrosine phosphatase

多效生长因子（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。虽然PTN对术后组织再生至关重要， 在细胞损伤的情况下，细胞因子的错误表达通常导致致病性病症。具体来说，PTN是 在大量癌症中过表达和PTN活性的降低降低了生长速率， 这些癌症的转移潜力。这表明PTN信号传导可能是治疗糖尿病的有价值的靶点。 疾病的数量然而，很少有人知道PTN信号的结构机制。我们想 研究调控PTN与受体型蛋白酪氨酸相互作用结构决定因子 磷酸酶ζ（PTPRZ），一种硫酸软骨素（CS）蛋白聚糖和与PTN相关的受体 促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联 PTPRZ通过与其糖胺聚糖链或核心蛋白结合，导致PTPRZ自身抑制。我们 我们想证实我们的模型，并研究是否GAG诱导的PTN寡聚体是必要的PTN信号。 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的亲和力， 糖胺聚糖的硫酸化依赖于聚糖的硫酸化密度和艾杜糖醛酸含量。我们还展示 PTN的C-末端尾部，已知对于PTPRZ信号传导至关重要，原因不明，对于 维持与在PTPRZ中发现的CS类型的稳定相互作用，并且PTN结合至 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。 交联我们还发现PTN寡聚化只发生在糖胺聚糖存在的情况下 并且PTN寡聚化界面最可能涉及PTN中的两个结构域。基础上 由于我们的初步研究取得了成功，我们希望进一步研究PTN信号转导的结构机制。 具体而言，我们建议：1）确定PTN-GAG复合物的结构，重点是过硫酸化 硫酸皮肤素，其可能是有效的PTN抑制剂。2)确定PTN的低聚物结构 和工程改造PTN的强制性单体，以检查PTN寡聚体在其与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，并找到其他可能的作用机制。 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活性的调节是不完全的。四、 研究PTN的活性是否与其使用新模型交联蛋白聚糖的能力相关 蛋白聚糖系统这个系统将允许我们测试交联是否依赖于核心蛋白， PTPRZ，并研究了聚糖硫酸化密度和长度对PTN交联和活性的影响。

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.