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%，但对它们的功能或全身激素参与调节它们的活性知之甚少。这些细胞占据骨的矿化基质深处的陷窝，并通过间隙连接彼此沟通并与成骨细胞沟通。我们最近报道骨细胞表达高水平的受体，其特异性识别PTH的羧基（C）末端部分，即CPTH受体。这些细胞来源于缺乏PTH 1 R的遗传改变的小鼠，并且普遍表达永生化的SV 40 T抗原，其允许建立条件永生化细胞系。在初步研究中，我们已经分离和表征了三种骨细胞系，它们似乎表达非常高的CPTHR。在这些细胞中，CPTHR的激活能够诱导凋亡以及增加连接蛋白43的量。此外，我们还证实了破骨细胞和破骨细胞前体细胞上存在CPTHR。似乎与PTH 1 R不同，这种新型受体也在骨髓中的造血细胞的表面上表达，在那里它可以影响成熟破骨细胞的数量，可能通过调节这些细胞的增殖、分化、融合或存活。本项目将解决两个主要目标：PTH对骨细胞凋亡的调节，以及CPTHRs激活对破骨细胞的影响。第一个目的是针对了解的分子机制的促凋亡作用的CPTH片段对骨细胞和潜在的功能相互作用的PTH 1 R和CPTHR在这些细胞中的激活。第二个目的是集中在分析CPTHR对破骨细胞和破骨细胞前体的作用机制。这些研究将为骨细胞和破骨细胞的功能以及完整的N-末端和C-末端PTH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.