Sharma Ritu, Colarusso Pina, Zhang Hong, Stevens Katarzyna M, Patel Kamala D
Department of Physiology and Pharmacology, University of Calgary; Calgary, AB T2N 4N1, Canada.
Department of Physiology and Pharmacology, University of Calgary; Calgary, AB T2N 4N1, Canada The Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
J Cell Sci. 2015 Feb 15;128(4):695-705. doi: 10.1242/jcs.156588. Epub 2014 Dec 12.
Focal adhesion kinase (FAK)-related nonkinase (PTK2 isoform 6 in humans, hereafter referred to as FRNK) is a cytoskeletal regulatory protein that has recently been shown to dampen lung fibrosis, yet its role in inflammation is unknown. Here, we show for the first time that expression of FRNK negatively regulates IL-4-mediated inflammation in a human model of eosinophil recruitment. Mechanistically, FRNK blocks eosinophil accumulation, firm adhesion and transmigration by preventing transcription and protein expression of VCAM-1 and CCL26. IL-4 activates STAT6 to induce VCAM-1 and CCL26 transcription. We now show that IL-4 also increases GATA6 to induce VCAM-1 expression. FRNK blocks IL-4-induced GATA6 transcription but has little effect on GATA6 protein expression and no effect on STAT6 activation. FRNK can block FAK or Pyk2 signaling and we, thus, downregulated these proteins using siRNA to determine whether signaling from either protein is involved in the regulation of VCAM-1 and CCL26. Knockdown of FAK, Pyk2 or both had no effect on VCAM-1 or CCL26 expression, which suggests that FRNK acts independently of FAK and Pyk2 signaling. Finally, we found that IL-4 induces the late expression of endogenous FRNK. In summary, FRNK represents a novel mechanism to negatively regulate IL-4-mediated inflammation.
粘着斑激酶（FAK）相关非激酶（人类中的PTK2亚型6，以下简称FRNK）是一种细胞骨架调节蛋白，最近已被证明可减轻肺纤维化，但其在炎症中的作用尚不清楚。在此，我们首次表明，在嗜酸性粒细胞募集的人类模型中，FRNK的表达负向调节IL-4介导的炎症。从机制上讲，FRNK通过阻止VCAM-1和CCL26的转录和蛋白表达来阻断嗜酸性粒细胞的积累、牢固粘附和迁移。IL-4激活STAT6以诱导VCAM-1和CCL26转录。我们现在表明，IL-4还增加GATA6以诱导VCAM-1表达。FRNK阻断IL-4诱导的GATA6转录，但对GATA6蛋白表达影响很小，对STAT6激活无影响。FRNK可以阻断FAK或Pyk2信号传导，因此，我们使用小干扰RNA下调这些蛋白，以确定来自这两种蛋白的信号是否参与VCAM-1和CCL26的调节。敲低FAK、Pyk2或两者对VCAM-1或CCL26表达均无影响，这表明FRNK的作用独立于FAK和Pyk2信号传导。最后，我们发现IL-4诱导内源性FRNK的晚期表达。总之，FRNK代表了一种负向调节IL-4介导炎症反应的新机制。
