探索 SLK 對黏著性細胞骨架的效應

Abstract

SLK(Ste20-like kinase)是一種絲胺酸/蘇胺酸蛋白激酶，參與了細胞遷移、細胞凋亡和細胞增殖等許多生物過程。它被確定為我們最近的合成運動障礙篩選的候選者之一，是因為我們觀察到透過同時抑制肌球蛋白活化劑ROCK和肌動蛋白調節劑SLK便可以協同性地增加集體細胞遷移的速度。儘管先前的研究表明SLK 可能直接抑制心肌細胞中的 RhoA-ROCK活性，但我們的結果並未揭示細胞遷移過程中 SLK和 ROCK 之間有直接訊號的相互作用。實驗結果還顯示，SLK knockdown改善了頭頸癌 SAS 細胞和人類皮膚角質細胞 HaCaT細胞的細胞排列整齊度和肌動蛋白結構。然後，就像之前文獻所報導的，我們證實 SLK能夠透過 Ezrin去改變肌動蛋白的結構。有趣的是，SLK knockdown對肌動蛋白結構的影響與Ezrin knockdown是極為相似的，但卻無法透過抑制Ezrin的磷酸化重現相似結果，顯示SLK 可能是透過非激酶的功能調節肌動蛋白。另外SLK knockdown可增加Ezrin從細胞質到細胞核的比例上升，但抑制Ezrin磷酸化則不會增加此現象，表示SLK是以非激酶依賴性方式調節Ezrin。 因此，我們推測非激酶依賴性方式的SLK-Ezrin組合會去調節肌動蛋白的細胞骨架以重塑細胞-細胞和細胞-基質黏附，這兩者對於細胞排列完整性和集體細胞遷移非常重要。我們現在正在致力於釐清非激酶依賴性方式的SLK-Ezrin如何調節黏附細胞骨架，最終目標是了解其在集體細胞遷移過程中與ROCK的協同合作模式。

SLK (Ste20-like kinase) is a serine/threonine protein kinase involved in many biological processes including cell migration, apoptosis and cell proliferation. It was identified as one of the candidates from our recent screen of synthetic dysmobility, as collective cell migration could be synergistically increased by simultaneous suppression of myosin activator ROCK and actin modulator SLK. Although previous research suggested that SLK might directly suppress RhoA-ROCK activities in cardiomyocytes, our results did not reveal direct signaling interactions between SLK and ROCK during cell migration. Our data also showed that knockdown of SLK improved cell alignment and actin structure in head and neck cancer SAS cells and human keratinocytes HaCaT cells. Then, we confirmed that SLK altered actin structures through Ezrin as reported previously. Intriguingly, effects of SLK knockdown on actin could be repeated by Ezrin knockdown, but not by inhibitor of Ezrin phosphorylation, suggesting that SLK modulated actin by non-kinase function. Moreover, translocation of Ezrin from cytosol into nucleui was increased by SLK knockdown, but not by inhibitor of Ezrin phosphorylation, indicating that SLK regulated Ezrin in kinase-independent manners. Therefore, we speculated that kinase-independent SLK-Ezrin regulates actin cytoskeletons to remodel cell-cell and cell-matrix adhesion, both of which are critical for cell sheet integrity and collective cell migration. We are now elucidating how kinase-independent SLK-Ezrin regulates adhesion cytoskeletons, with the ultimate goal of understanding its mode of synergistic collaboration with ROCK during collective cell migration.