Arkett S A, Dixon S J, Sims S M
Department of Physiology, University of Western Ontario, London, Canada.
J Cell Sci. 1994 Feb;107 ( Pt 2):517-26.
Osteoclasts are the cells responsible for the resorption of bone and other mineralized tissues. GTP-binding proteins (G proteins) play important roles in regulating the activity of many cell types; however, there is limited knowledge of their functions in osteoclasts. We used the patch-clamp technique in the whole-cell configuration to introduce either hydrolysis-resistant guanosine triphosphate analogues or fluoroaluminate into single rat osteoclasts, and examined the effects of G protein activation on cell morphology and ionic conductances. Guanosine 5'-O-(3-thiotriphosphate) or 5'-guanylyl-imidodiphosphate, but not the control compounds adenosine 5'-O-(3-thiotriphosphate) or guanosine 5'-O-(2-thiodiphosphate), induced: (1) prompt spreading due to extension of lamellipodia; and (2) after a latency of several minutes, complete suppression of the inwardly rectifying K+ current. Pertussis toxin did not alter either spreading or suppression of K+ current induced by guanosine 5'-O-(3-thiotriphosphate). Cytochalasin D, but not colchicine, prevented guanosine 5'-O-(3-thiotriphosphate)-induced spreading, consistent with actin polymerization underlying lamellipod extension. Whole-cell capacitance did not change during guanosine 5'-O-(3-thiotriphosphate)-induced spreading, which is consistent with a lack of change in total plasma membrane area. Fluoroaluminate did not induce spreading, but it did suppress the K+ current. The differential effects of fluoroaluminate and guanosine 5'-O-(3-thiotriphosphate) suggest that lamellipod extension is regulated by a small molecular mass, monomeric G protein, whereas the inwardly rectifying K+ current is regulated by a large molecular mass, heterotrimeric G protein. Thus, osteoclast motility and ion transport are regulated by separate G protein-coupled pathways.
破骨细胞是负责骨和其他矿化组织吸收的细胞。GTP结合蛋白（G蛋白）在调节多种细胞类型的活性中起重要作用；然而，关于它们在破骨细胞中的功能了解有限。我们采用全细胞膜片钳技术，将抗水解的鸟苷三磷酸类似物或氟铝酸盐引入单个大鼠破骨细胞中，并研究G蛋白激活对细胞形态和离子电导的影响。5'-O-(3-硫代三磷酸)鸟苷或5'-鸟苷酰亚胺二磷酸，但不是对照化合物5'-O-(3-硫代三磷酸)腺苷或5'-O-(2-硫代二磷酸)鸟苷，诱导：(1)由于片状伪足的伸展而迅速铺展；(2)几分钟的延迟后，内向整流钾电流完全被抑制。百日咳毒素既不改变5'-O-(3-硫代三磷酸)鸟苷诱导的铺展，也不改变钾电流的抑制。细胞松弛素D而非秋水仙碱可阻止5'-O-(3-硫代三磷酸)鸟苷诱导的铺展，这与片状伪足伸展所依赖的肌动蛋白聚合一致。在5'-O-(3-硫代三磷酸)鸟苷诱导的铺展过程中，全细胞电容没有变化，这与总质膜面积缺乏变化一致。氟铝酸盐不诱导铺展，但它确实抑制钾电流。氟铝酸盐和5'-O-(3-硫代三磷酸)鸟苷的不同作用表明，片状伪足的伸展由小分子质量的单体G蛋白调节，而内向整流钾电流由大分子质量的异三聚体G蛋白调节。因此，破骨细胞的运动性和离子转运由不同的G蛋白偶联途径调节。
