Department of Pediatrics, Neil Bogart Memorial Laboratories, Division of Hematology-Oncology, Saban Research Institute at Childrens Hospital Los Angeles, USA.
Blood. 2010 Apr 1;115(13):2709-18. doi: 10.1182/blood-2009-05-223776. Epub 2010 Feb 2.
Inhibition of integrins alphavbeta3 and alphavbeta5 in human brain microvascular endothelial cells (HBMECs) by the function-blocking peptide RGDfV induces loss of spreading on vitronectin, cell detachment, and apoptosis. We demonstrate that cell detachment is not required for apoptosis because plating on bovine serum albumin-blocked poly-L-lysine (allows attachment, but not integrin ligation and cell spreading) also induced apoptosis. Latrunculin B (LatB), which inhibits F-actin polymerization, induced transient loss of HBMEC spreading on vitronectin, but not their detachment, and induced apoptosis despite recovery of cell spreading. However, LatB did not cause apoptosis in 5 tumor cell lines. In HBMECs, both LatB and RGDfV induced transient Y412 and Y245 phosphorylation of endogenous c-Abl, a nonreceptor tyrosine kinase that reciprocally regulates F-actin. LatB also induced nuclear translocation of c-Abl in HBMECs. STI-571 (imatinib), a targeted therapy for BCR-ABL1(+) leukemias and inhibitor of c-Abl, platelet-derived growth factor receptor, and c-Kit, decreased endothelial apoptosis. LatB-induced HBMEC apoptosis, and its inhibition by STI-571 also occurred in a 3-dimensional collagen model, supporting physiologic relevance. Last, siRNA to c-Abl (but not nonspecific siRNA) also inhibited RGDfV- and LatB-induced apoptosis. Thus, endogenous c-Abl mediates endothelial apoptosis induced by inhibition of integrins alphavbeta3/alphavbeta5 or by LatB-induced disruption of F-actin.
整合素 alphavbeta3 和 alphavbeta5 在人脑血管内皮细胞（HBMEC）中的功能阻断肽 RGDfV 的抑制作用导致在 vitronectin 上的扩散丧失、细胞脱落和细胞凋亡。我们证明细胞脱落不是细胞凋亡所必需的，因为铺板在牛血清白蛋白阻断的多聚-L-赖氨酸上（允许附着，但不允许整合素连接和细胞扩散）也诱导细胞凋亡。Latrunculin B（LatB），它抑制 F-肌动蛋白聚合，诱导 HBMEC 在 vitronectin 上的短暂扩散丧失，但不引起细胞脱落，并诱导细胞凋亡，尽管细胞扩散得到恢复。然而，LatB 不会引起 5 种肿瘤细胞系的细胞凋亡。在 HBMEC 中，LatB 和 RGDfV 都诱导内源性 c-Abl 的 Y412 和 Y245 短暂磷酸化，c-Abl 是一种非受体酪氨酸激酶，可相互调节 F-肌动蛋白。LatB 还诱导 HBMEC 中的 c-Abl 核易位。STI-571（伊马替尼），一种针对 BCR-ABL1（+）白血病的靶向治疗药物，也是 c-Abl、血小板衍生生长因子受体和 c-Kit 的抑制剂，可降低内皮细胞凋亡。LatB 诱导的 HBMEC 凋亡，以及 STI-571 对其的抑制作用，也发生在 3 维胶原模型中，支持生理相关性。最后，c-Abl 的 siRNA（但不是非特异性 siRNA）也抑制了 RGDfV 和 LatB 诱导的细胞凋亡。因此，内源性 c-Abl 介导整合素 alphavbeta3/alphavbeta5 抑制或 LatB 诱导的 F-肌动蛋白破坏引起的内皮细胞凋亡。
