Oike Masahiro, Watanabe Michi, Kimura Chiwaka
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Biochim Biophys Acta. 2008 Oct;1780(10):1148-55. doi: 10.1016/j.bbagen.2008.07.004. Epub 2008 Jul 17.
Hypotonic stress (HTS) induces various responses in vascular endothelium, but the molecules involved in sensing HTS are not known. To investigate a possible role of heparan sulfate proteoglycan (HSPG) in sensing HTS, we compared the responses of control bovine aortic endothelial cells (BAECs) with those of cells treated with heparinase III, which exclusively degrades HSPG. Tyrosine phosphorylation of 125 kDa FAK induced by HTS (-30%) in control cells was abolished in heparinase III-treated BAECs. The amplitude of the volume-regulated anion channel (VRAC) current, whose activation is regulated by tyrosine kinase, was significantly reduced by the treatment with heparinase III. Also, HTS-induced ATP release through the VRAC pore and the concomitant Ca(2+) transients were significantly reduced in the heparinase III-treated BAECs. In contrast, exogenously applied ATP evoked similar Ca(2+) transients in both control and heparinase III-treated BAECs. The transient formation of actin stress fibers induced by HTS in control cells was absent in heparinase III-treated BAECs. Lysophosphatidic acid (LPA) also induced FAK phosphorylation, actin reorganization and ATP release in control BAECs, but heparinase III did not affect these LPA-induced responses. We conclude from these observations that HSPG is one of the sensory molecules of hypotonic cell swelling in BAECs.
低渗应激（HTS）可诱导血管内皮细胞产生多种反应，但参与感知HTS的分子尚不清楚。为了研究硫酸乙酰肝素蛋白聚糖（HSPG）在感知HTS中的可能作用，我们比较了对照牛主动脉内皮细胞（BAECs）与用肝素酶III处理的细胞的反应，肝素酶III专门降解HSPG。在对照细胞中由HTS（-30%）诱导的125 kDa黏着斑激酶（FAK）的酪氨酸磷酸化在肝素酶III处理的BAECs中被消除。体积调节性阴离子通道（VRAC）电流的幅度，其激活受酪氨酸激酶调节，在用肝素酶III处理后显著降低。此外，在肝素酶III处理的BAECs中，HTS诱导的通过VRAC孔的ATP释放以及伴随的Ca(2+)瞬变显著减少。相反，外源性施加的ATP在对照和肝素酶III处理的BAECs中诱发相似的Ca(2+)瞬变。在对照细胞中由HTS诱导的肌动蛋白应力纤维的瞬时形成在肝素酶III处理的BAECs中不存在。溶血磷脂酸（LPA）在对照BAECs中也诱导FAK磷酸化、肌动蛋白重组和ATP释放，但肝素酶III不影响这些LPA诱导的反应。我们从这些观察结果得出结论，HSPG是BAECs中低渗性细胞肿胀的传感分子之一。
