Lorenzi O, Frieden M, Villemin P, Fournier M, Foti M, Vischer U M
Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
J Thromb Haemost. 2008 Nov;6(11):1962-9. doi: 10.1111/j.1538-7836.2008.03138.x.
Vascular endothelial growth factor (VEGF) and histamine induce von Willebrand factor (VWF) release from vascular endothelial cells. Protein kinase C (PKC) is involved in the control of exocytosis in many secretory cell types.
We investigated the role of PKC and the interactions between PKC and Ca2+ signaling in both VEGF-induced and histamine-induced VWF secretion from human umbilical vein endothelial cells (HUVECs).
Several PKC inhibitors (staurosporine, Ro31-8220, myristoylated PKC peptide inhibitor and Go6983) block VEGF-induced but not histamine-induced VWF secretion. PKC-alpha and novel PKCs (PKC-delta, PKC-epsilon, and PKC-eta), but not PKC-beta, are expressed in HUVECs. Both VEGF and histamine activate PKC-delta. However, gene inactivation experiments using small interfering RNA indicate that PKC-delta (but not PKC-alpha) is involved in the regulation of VEGF-induced but not histamine-induced secretion. Both VEGF and histamine induce a rise in cytosolic free Ca2+ ([Ca2+]c), but the response to VEGF is weaker and even absent in a significant subset of cells. Furthermore, VEGF-induced secretion is largely preserved when the rise in [Ca2+]c is prevented by BAPTA-AM.
Our study identifies striking agonist specificities in signal-secretion coupling. Histamine-induced secretion is dependent on [Ca2+]c but not PKC, whereas VEGF-induced secretion is largely dependent on PKC-delta and significantly less on [Ca2+]c. Our data firmly establish the key role of PKC-delta in VEGF-induced VWF release, but suggest that a third, VEGF-specific, signaling intermediate is required as a PKC-delta coactivator.
血管内皮生长因子（VEGF）和组胺可诱导血管性血友病因子（VWF）从血管内皮细胞释放。蛋白激酶C（PKC）参与多种分泌细胞类型的胞吐作用调控。
我们研究了PKC的作用以及PKC与Ca2+信号在人脐静脉内皮细胞（HUVECs）中VEGF诱导和组胺诱导的VWF分泌过程中的相互作用。
几种PKC抑制剂（星形孢菌素、Ro31-8220、肉豆蔻酰化PKC肽抑制剂和Go6983）可阻断VEGF诱导的而非组胺诱导的VWF分泌。PKC-α和新型PKC（PKC-δ、PKC-ε和PKC-η）在HUVECs中有表达，但PKC-β没有。VEGF和组胺均可激活PKC-δ。然而，使用小干扰RNA进行的基因失活实验表明，PKC-δ（而非PKC-α）参与VEGF诱导的而非组胺诱导的分泌调控。VEGF和组胺均可诱导胞质游离Ca2+（[Ca2+]c）升高，但在相当一部分细胞中，对VEGF的反应较弱甚至没有反应。此外，当BAPTA-AM阻止[Ca2+]c升高时，VEGF诱导的分泌在很大程度上得以保留。
我们的研究确定了信号-分泌偶联中显著的激动剂特异性。组胺诱导的分泌依赖于[Ca2+]c而非PKC，而VEGF诱导的分泌在很大程度上依赖于PKC-δ，对[Ca2+]c的依赖性显著较低。我们的数据明确了PKC-δ在VEGF诱导的VWF释放中的关键作用，但表明需要第三种VEGF特异性信号中间体作为PKC-δ的共激活剂。
