Calcitonin-induced changes in the cytoskeleton are mediated by a signal pathway associated with protein kinase A in osteoclasts
Calcitonin-induced changes in the cytoskeleton are mediated by a signal pathway associated with protein kinase A in osteoclasts
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DOI：
10.1210/en.137.11.4685
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发表时间：
1996-11-01
期刊：
影响因子：
4.8
通讯作者：
Suda, T
中科院分区：
文献类型：
--
作者：
Suzuki, H;Nakamura, I;Suda, T
已知降钙素通过其受体抑制破骨细胞的骨吸收，所述受体在破骨细胞的质膜上大量表达。近年来研究发现降钙素受体与cAMP依赖性蛋白激酶（PKA）和蛋白激酶C（PKC）均偶联。为了研究PKA和PKC途径如何参与降钙素的作用，我们专注于体外形成的小鼠破骨细胞样多核细胞（OCL）的细胞骨架的变化。当OCL在牙本质切片上培养时，它们形成吸收陷窝和F-肌动蛋白点（肌动蛋白环）的环形结构。Elcatonin，鳗鱼降钙素的合成类似物，破坏肌动蛋白环，抑制坑的形成，在剂量依赖性的方式。毛喉素和二丁酰cAMP，这两者都有能力激活PKA，模仿elcatonin的效果。具有激活PKC活性的佛波醇肉豆蔻酸酯和佛波醇12，13-二丁酸酯也能抑制OCL的pit形成活性，但对肌动蛋白环的影响不大。用cAMP拮抗剂Rp-cAMPs处理后，elcatonin对小凹形成和肌动蛋白环形成的抑制作用部分恢复。依卡宁诱导PKA活性在几分钟内迅速增加，其激活依卡宁发生在剂量依赖性的方式。elcatonin激活PKA的时间和剂量依赖性曲线与破坏肌动蛋白环的曲线相似。此外，在培养皿上，将活化的PKA显微注射到OCL中在10分钟内破坏肌动蛋白环。肌动蛋白环的影响不大的PKA预孵育与cAMP依赖性蛋白激酶抑制剂（IP-20）到OCL的显微注射。这些结果表明，PRA激活，而不是PKC激活，参与介导降钙素的影响，通过破坏肌动蛋白组织。
Calcitonin is known to inhibit osteoclastic bone resorption through its receptor, which is abundantly expressed on the plasma membrane of osteoclasts. Recently, it was reported that calcitonin receptors were coupled to both cAMP-dependent protein kinase (PKA) and protein kinase C (PKC). To examine how the PKA and PKC pathways are involved in the effects of calcitonin, we focused on changes in the cytoskeleton of murine osteoclast-like multinucleated cells (OCLs) formed in vitro. When OCLs were cultured on dentine slices, they formed resorption pits and ringed structures of F-actin dots (actin rings). Elcatonin, a synthetic analogue of eel calcitonin, disrupted actin rings and inhibited pit formation in a dose-dependent manner. Forskolin and dibutyryl cAMP, both of which have the ability to activate PKA, mimicked the effects of elcatonin. Phorbol myristate acetate and phorbol 12,13-dibutyrate, both of which have the ability to activate PKC, also inhibited pit-forming activity, but little affected actin rings of OCLs. The inhibitory effects of elcatonin on the pit formation and actin ring formation were partially restored by the treatment with Rp-cAMPs, a cAMP antagonist. Elcatonin induced a rapid increase in PKA activity within a few minutes, and its activation by elcatonin occurred in a dose-dependent manner. The time- and dose-dependent profiles of elcatonin for the activation of PKA were similar to those for the disruption of actin rings. Moreover, microinjection of activated PKA into OCLs disrupted actin rings within 10 min on culture dishes. Actin rings were little affected by the microinjection of the PKA preincubated with a cAMP-dependent protein kinase inhibitor (IP-20) into OCLs. These results suggest that PRA activation, rather than PKC activation, is involved in mediating the effects of calcitonin, through the disruption of actin organization.