P2X7 nucleotide receptors mediate blebbing in osteoblasts through a pathway involving lysophosphatidic acid
P2X7 nucleotide receptors mediate blebbing in osteoblasts through a pathway involving lysophosphatidic acid
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DOI：
10.1074/jbc.m605620200
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发表时间：
2007-02-02
影响因子：
4.8
通讯作者：
Dixon, S. Jeffrey
中科院分区：
文献类型：
--
作者：
Panupinthu, Nattapon;Zhao, Lin;Dixon, S. Jeffrey
细胞外核苷酸，释放响应机械或炎症刺激，信号通过P2受体在许多细胞类型，包括成骨细胞。P2X7受体是ATP门控阳离子通道，可诱导大膜孔的形成。编码P2X7受体的基因的破坏导致骨膜骨形成减少和骨骼对机械刺激不敏感。我们的目的是研究成骨细胞中与P2X7激活相关的信号通路。活细胞成像显示，ATP或2 '，3'-O-（4-苯甲酰基苯甲酰基）-ATP（BzATP），而不是UTP，UDP或2-甲硫基-ADP，诱导动态膜起泡在颅骨成骨细胞。在来自野生型但不是P2X7敲除小鼠的颅骨细胞中观察到起泡。P2X7受体与磷脂酶D和A2的活化偶联，抑制磷脂酶D和A2抑制BzATP诱导的起泡。这些磷脂酶的活化导致溶血磷脂酸（LPA）的产生。LPA引起野生型和P2X7基因敲除小鼠成骨细胞的动态起泡，类似于野生型细胞中BzATP诱导的起泡。然而，LPA诱导的起泡发作更快，并且不受磷脂酶D或A2抑制的影响。LPA受体的阻断或脱敏抑制了对LPA和BzATP的反应，而不影响P2X7刺激的孔形成。因此，LPA在P2X7受体下游起作用以诱导膜起泡。此外，Rho相关激酶的抑制消除BzATP和LPA诱导的起泡。总之，我们提出了一种新的信号转导轴，通过磷脂酶P2X7受体的生产LPA和激活Rho相关激酶。该途径可能有助于骨骼发育和机械传导过程中P2X7刺激的骨生成。
Extracellular nucleotides, released in response to mechanical or inflammatory stimuli, signal through P2 receptors in many cell types, including osteoblasts. P2X7 receptors are ATP-gated cation channels that can induce formation of large membrane pores. Disruption of the gene encoding the P2X7 receptor leads to decreased periosteal bone formation and insensitivity of the skeleton to mechanical stimulation. Our purpose was to investigate signaling pathways coupled to P2X7 activation in osteoblasts. Live cell imaging showed that ATP or 2', 3'-O-(4-benzoylbenzoyl)-ATP (BzATP), but not UTP, UDP, or 2-methylthio-ADP, induced dynamic membrane blebbing in calvarial osteoblasts. Blebbing was observed in calvarial cells from wildtype but not P2X7 knock-out mice. P2X7 receptors coupled to activation of phospholipase D and A2, inhibition of which suppressed BzATP-induced blebbing. Activation of these phospholipases leads to production of lysophosphatidic acid (LPA). LPA caused dynamic blebbing in osteoblasts from both wild-type and P2X7 knock-out mice, similar to that induced by BzATP in wildtype cells. However, LPA-induced blebbing was more rapid in onset and was not affected by inhibition of phospholipase D or A2. Blockade or desensitization of LPA receptors suppressed blebbing in response to LPA and BzATP, without affecting P2X7-stimulated pore formation. Thus, LPA functions downstream of P2X7 receptors to induce membrane blebbing. Furthermore, inhibition of Rho-associated kinase abolished blebbing induced by both BzATP and LPA. In summary, we propose a novel signaling axis that links P2X7 receptors through phospholipases to production of LPA and activation of Rho-associated kinase. This pathway may contribute to P2X7-stimulated osteogenesis during skeletal development and mechanotransduction.