期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：27
页码：8314-8319
DOI：10.1073/pnas.1505421112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceAlternative splicing is the main mechanism that drives protein diversity; however, little is known about the physiological cues that control splicing. Here, we show that the stiffness of the extracellular matrix mediates protein splicing in cells both in vitro and in vivo. Alternative splicing mediated by matrix stiffness occurs through the phosphorylation of splicing regulatory factors, serine/arginine rich (SR) proteins, and depends on the PI3K signaling pathway. Because the SR family of proteins are conserved among both vertebrates and invertebrates and are known to also be involved in genome stabilization, translation, and mRNA export, these results suggest a previously unidentified mechanism by which cells can respond and adapt to their mechanical microenvironment in both healthy and diseased states. Alternative splicing of proteins gives rise to different isoforms that play a crucial role in regulating several cellular processes. Notably, splicing profiles are altered in several cancer types, and these profiles are believed to be involved in driving the oncogenic process. Although the importance of alternative splicing alterations occurring during cancer is increasingly appreciated, the underlying regulatory mechanisms remain poorly understood. In this study, we use both biochemical and physical tools coupled with engineered models, patient samples, and a murine model to investigate the role of the mechanical properties of the tumor microenvironment in regulating the production of the extra domain-B (EDB) splice variant of fibronectin (FN), a hallmark of tumor angiogenesis. Specifically, we show that the amount of EDB-FN produced by endothelial cells increases with matrix stiffness both in vitro and within mouse mammary tumors. Matrix stiffness regulates splicing through the activation of serine/arginine rich (SR) proteins, the splicing factors involved in the production of FN isoforms. Activation of the SR proteins by matrix stiffness and the subsequent production of EDB-FN are dependent on intracellular contractility and PI3K-AKT signaling. Notably, matrix stiffness-mediated splicing is not limited to EDB-FN, but also affects splicing in the production of PKC {beta}II and the VEGF 165b splice variant. Together, these results demonstrate that the mechanical properties of the microenvironment regulate alternative splicing and establish a previously unidentified mechanism by which cells can adapt to their microenvironment.
