The Lbc Rho Guanine Nucleotide Exchange Factor/α-Catulin Axis Functions in Serotonin-induced Vascular Smooth Muscle Cell Mitogenesis and RhoA/ROCK Activation
The Lbc Rho Guanine Nucleotide Exchange Factor/α-Catulin Axis Functions in Serotonin-induced Vascular Smooth Muscle Cell Mitogenesis and RhoA/ROCK Activation
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DOI：
10.1074/jbc.m109.062513
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发表时间：
2010-10-22
影响因子：
4.8
通讯作者：
Toksoz, Deniz
中科院分区：
文献类型：
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作者：
Bear, Michael D.;Li, Min;Toksoz, Deniz
5-羟色胺（5-hydroxytryptamine，5-HT）对包括肺动脉平滑肌细胞（pulmonary arterial smooth muscle cells，PASMC）在内的多种细胞类型具有促有丝分裂作用，并与肺动脉高压中发生的异常血管平滑肌重塑有关。RhoA/Rho激酶（ROCK）功能是5-HT诱导的PASMC有丝分裂所必需的，并且5-HT激活RhoA;然而，信号传导步骤定义不清。Rho鸟嘌呤核苷酸交换因子（Rho GEFs）将细胞外信号传递给Rho，我们发现5-HT处理PASMC导致膜相关Lbc Rho GEFs增加，表明5-HT的调节作用。Lbc敲低siRNA减弱了5-HT诱导的PASMC胸苷摄取，表明在PASMC有丝分裂中的作用。5-HT触发了PASMC中Rho依赖性血清反应因子介导的报告基因激活，Lbc耗竭可降低这种激活。Lbc基因敲低可降低5-HT诱导的RhoA/ROCK激活，但不能降低p42/44 ERK MAP激酶激活，表明Lbc是5-HT和RhoA/ROCK之间的中介，而不是ERK。PASMC的5-HT刺激导致Lbc、RhoA和α-catulin支架之间的关联增加。此外，α-catulin敲低减弱5-HT诱导的PASMC胸苷摄取。5-HT诱导的PASMC有丝分裂被显性负性G（q）蛋白降低，表明与Lbc/α-catulin协同作用。这些结果首次定义了Rho GEF参与血管平滑肌细胞生长和5-羟色胺信号传导，并表明Lbc Rho GEF家族成员发挥不同的作用。因此，Lbc/α-catulin轴参与5-HT诱导的PASMC有丝分裂和RhoA/ROCK信号传导，并且可能是涉及血管平滑肌重塑的疾病的干预靶点。
Serotonin (5-hydroxytryptamine, 5-HT) is mitogenic for several cell types including pulmonary arterial smooth muscle cells (PASMC), and is associated with the abnormal vascular smooth muscle remodeling that occurs in pulmonary arterial hypertension. RhoA/Rho kinase (ROCK) function is required for 5-HT-induced PASMC mitogenesis, and 5-HT activates RhoA; however, the signaling steps are poorly defined. Rho guanine nucleotide exchange factors (Rho GEFs) transduce extracellular signals to Rho, and we found that 5-HT treatment of PASMC led to increased membrane-associated Lbc Rho GEF, suggesting modulation by 5-HT. Lbc knockdown by siRNA attenuated 5-HT-induced thymidine uptake in PASMC, indicating a role in PASMC mitogenesis. 5-HT triggered Rho-dependent serum response factor-mediated reporter activation in PASMC, and this was reduced by Lbc depletion. Lbc knockdown reduced 5-HT-induced RhoA/ROCK activation, but not p42/44 ERK MAP kinase activation, suggesting that Lbc is an intermediary between 5-HT and RhoA/ROCK, but not ERK. 5-HT stimulation of PASMC led to increased association between Lbc, RhoA, and the alpha-catulin scaffold. Furthermore, alpha-catulin knockdown attenuated 5-HT-induced PASMC thymidine uptake. 5-HT-induced PASMC mitogenesis was reduced by dominant-negative G(q) protein, suggesting cooperation with Lbc/alpha-catulin. These results for the first time define a Rho GEF involved in vascular smooth muscle cell growth and serotonin signaling, and suggest that Lbc Rho GEF family members play distinct roles. Thus, the Lbc/alpha-catulin axis participates in 5-HT-induced PASMC mitogenesis and RhoA/ROCK signaling, and may be an interventional target in diseases involving vascular smooth muscle remodeling.