OSTEOBLAST NUCLEAR MATRIX REGULATION OF COLLAGEN

间断性剂量的甲状旁腺激素（PTH）通过选择性刺激骨形成来增加骨量。介导这种合成代谢作用的分子机制尚不清楚。在体外模型中证明这种现象是有问题的，因为甲状旁腺激素会减弱成骨细胞培养中的胶原合成。细胞结构影响胶原合成，并可能导致骨和培养成骨细胞对甲状旁腺激素的相反反应。我们认为胶原蛋白的表达是通过组织基质、细胞外基质、细胞骨架和核基质的相互连接蛋白与细胞结构耦合的。此外，我们提出这种结构途径的高潮是核基质结构转录因子，这些蛋白质通过弯曲启动子DNA来改变基因活性，以响应组织基质组织的变化。因此，pth诱导的组织基质蛋白的变化可能通过“拉扯”基因和改变启动子的几何形状来改变COL1A1的表达。我们已经发现了一个新的核基质结构转录因子家族，NP/NMP4，它以序列特异性结合大鼠I型胶原α 1 (I)多肽链（COL1A1）的启动子。这些独特的锌指蛋白与COL1A1启动子结合，使其弯曲，并含有基础启动子活性。PTH调节NP/NMP4- col1a1结合活性和NP/NMP4 mRNA表达。激素诱导的NP/NMP4-COL1A1结合的改变在骨和培养物之间是不同的。我们的目标是研究NP/NMP4在介导基础和pth调节的COL1A1转录中的功能作用。第一项研究将验证COL1A1启动子NP/NMP4结合元件在体外和体内参与成骨细胞基础和甲状旁腺激素调节的转录的假设。第二项研究将确定NP和NMP4在介导基础和pth调节的COL1A1转录中的不同功能。第三项研究将确定NP/NMP4蛋白的功能域。这一信息将确定成骨细胞中甲状旁腺激素作用的结构途径，并进一步阐明这种激素对骨的合成代谢作用的细胞基础。

Intermittent doses of parathyroid hormone (PTH) increase bone mass by selectively stimulating bone formation. The molecular mechanisms mediating this anabolic effect are unknown. Demonstrating this phenomenon is problematic using in vitro models because PTH attenuates collagen synthesis in osteoblast culture. Cell structure influences collagen synthesis and likely contributes to the opposing responses of bone and cultured osteoblasts to PTH. We propose that collagen expression is coupled to cell structure via the tissue matrix, the interlinking proteins of the extracellular matrix, cytoskeleton, and nuclear matrix. Furthermore, we propose that this structural pathway culminates with nuclear matrix architectural transcription factors, proteins that alter gene activity by bending promoter DNA in response to changes in tissue matrix organization. Therefore, PTH-induced changes in tissue matrix proteins may alter COL1A1 expression by "tugging" at the gene and altering promoter geometry. We have identified a novel family of nuclear matrix architectural transcription factors, NP/NMP4, that bind with sequence specificity to the promoter of the rat alpha1 (I) polypeptide chain (COL1A1) of type I collagen. These unique zinc finger proteins bind to the COL1A1 promoter, bend it, and contain basal promoter activity. PTH regulates NP/NMP4-COL1A1 binding activity and NP/NMP4 mRNA expression. Hormone-induced alterations in NP/NMP4-COL1A1 binding differ between bone and culture. Our goal is to investigate the functional role of NP/NMP4 in mediating basal and PTH-regulated COL1A1 transcription. The first study will test the hypothesis that the COL1A1 promoter NP/NMP4 binding elements contribute to osteoblast basal and PTH-modulated transcription in vitro and in vivo. The second study will determine the distinct functions of NP and NMP4 in mediating basal and PTH-regulated COL1A1 transcription. The third study will determine the functional domains of the NP/NMP4 proteins. This information will define a structural pathway for PTH action in osteoblasts and further clarify the cellular basis for the anabolic action of this hormone on bone.