NHERF-Mediated PTH Signaling in Mineral Ion Homeostasis

PTH对骨、肾和整体矿物质离子稳态的生物学作用中，刺激PTH/PTHrP受体，激活靶细胞内独特的信号通路（包括腺苷酸环化酶、磷脂酶C、磷脂酶C非依赖性蛋白激酶C和钙通道）。越来越多的证据表明，这些独特的途径在骨和肾细胞功能中具有可识别的差异，这导致了对信号选择性及其细胞作用的研究增加。Na+/H+交换调节因子（NHERFs）（信号调节细胞内支架蛋白的组成部分）最近被我们的团队证明可以作为“分子开关”，增加PTH对PLC途径的激活并抑制腺苷酸环化酶途径。由合作者进行的NHERF-1基因敲除具有骨质减少的骨骼表型。现在已经在骨细胞系中发现了nherf。缺乏NHERF的负鼠肾细胞系（OK）缺乏通常的PTH刺激的磷酸盐摄取阻断。NHERF转染后，这种缺陷被逆转，野生型OK细胞系功能恢复。该细胞系可作为pth介导的小管re-抑制的模型

In its biological actions on bone and kidney and overall mineral ion homeostasis, PTH stimulates the PTH/PTHrP receptor and activates distinctive signalling pathways within target cells (including adenylyl cyclase, phospholipase C, phospholipase-C independent protein kinase C and calcium channels). Growing evidence that some of these distinctive pathways have discernable differences in bone and renal cell function has led to increased study of signal selectivity and its cellular role. Na+/H+exchange regulatory factors (NHERFs) (components of signal modulating intracellular scaffold proteins) have recently been shown by our group to act as "molecular switches" that increase activation by PTH of the PLC pathway and suppress the adenylyl cyclase pathway. A gene knockout of NHERF-1, performed by collaborators, has an osteopenic skeletal phenotype. NHERFs have now been identified in bone cell lines. An opossum kidney cell line (OK) which is deficient in NHERF lacks the usual PTH stimulated blockade of phosphate uptake. The deficiency is reversed and wild type OK cell line function restored by NHERF transfection. This cell line serves as a model of PTH-mediated inhibition of tubular re- absorption of phosphate. Our specific aims are therefore: AIM I. Analyze the functional role of NHERFs with respect to PTH signaling and cell morphology in an opossum kidney cell model, comparing cell lines that are NHERF intact, defective and repleted. AIM II. Study the role of the NHERF/PTH1R complex in PTH signaling in bone cell lines in vitro. AIM III. Study the role of NHERF-1 in mediating the actions of PTH in bone, both in vitro and in vivo, working with the NHERF- 1 -/- mice provided by our colleagues for assessment of cellular mechanisms responsible for the skeletal phenotype.