Amino and Carboxyl Terminal PTH Receptors in Osteocytes

描述(由申请人提供)： 骨细胞占所有骨细胞的90%，但对其功能或系统激素对其活动的调节知之甚少(S)。这些细胞占据骨矿化基质深处的陷窝，彼此之间以及通过缝隙连接与成骨细胞进行交流。我们最近报道，骨细胞表达高水平的受体，特异性识别甲状旁腺激素的羧基(C)末端部分，CPTH受体。这些细胞来自缺乏PTH1R的转基因小鼠，并普遍表达永生化的SV40T抗原，从而建立有条件的永生化细胞系。在初步研究中，我们分离并鉴定了三种骨细胞系，它们似乎表达非常高的CPTHR。在这些细胞中，CPTHR的激活能够诱导细胞凋亡，并增加连接蛋白43的数量。此外，我们还证明了CPTHR存在于破骨细胞和破骨细胞前体细胞上。与PTH1R不同的是，这种新的受体也表达在骨髓造血细胞的表面，在那里它可以影响成熟破骨细胞的数量，可能是通过调节这些细胞的增殖、分化、融合或存活。该项目将解决两个主要目标：甲状旁腺素对骨细胞凋亡的调节，以及CPTHRs激活对破骨细胞的影响。第一个目的是了解CPTH片段对骨细胞促凋亡作用的分子机制，以及PTH1R和CPTHR激活在这些细胞中潜在的功能相互作用。第二个目的是分析CPTHR对破骨细胞和破骨细胞前体的作用机制。这些研究将为了解骨细胞和破骨细胞的功能以及完整的、N端和C端甲状旁腺激素在调节其行为中的作用提供新的见解。

DESCRIPTION (provided by applicant): Osteocytes comprise 90% of all bone cells, yet little is known of their function(s) or of the involvement of systemic hormones in regulating their activity. These cells occupy lacunae deep within the mineralized matrix of bone and communicate with one another and with osteoblasts via gap junctions. We have recently reported that osteocytes express high level of receptor that specifically recognizes the carboxyl(C)-terminal portion of PTH, the CPTH receptor. These cells derived from genetically altered mice that lack the PTH1R and ubiquitously express an immortalizing SV40 T-antigen that allows the establishment of conditionally immortalized cells lines. In preliminary studies we have isolated and characterized three osteocytic cell lines that appear to express very high CPTHRs. In these cells activation of the CPTHRs was able to induce apoptosis as well increase the amount of connexin 43. In addition, we also demonstrated the presence of CPTHRs on osteoclasts and osteoclast precursors. It appears that, unlike the PTH1R, this novel receptor is expressed also on the surface of hematopoietic cells in the bone marrow, where is can affect the number of mature osteoclasts, possibly by modulating proliferation, differentiation, fusion or survival of these cells. This project will address two main aims: PTH regulation of apoptosis in osteocytes, and the effect of CPTHRs activation on osteoclasts. The first aim is directed towards understanding the molecular mechanisms underlying the proapoptotic effect of CPTH fragments on osteocytes and the potential functional interaction of PTH1R and CPTHR activation in these cells. The second aim is focused on the analysis of the mechanisms of action of CPTHRs on osteoclasts and osteoclast precursors. These studies will provide new insight into osteocytes and osteoclasts function and of the role of intact, N-terminal and C-terminal PTH in regulating their behavior.