Downregulation of uPAR promotes urokinase translocation into the nucleus and epithelial to mesenchymal transition in neuroblastoma

Abstract

The urokinase system is involved in a variety of physiological processes, such as fibrinolysis, matrix remodeling, wound healing, and regeneration. Upon binding to its cognate receptor urokinase-type plasminogen activator receptor (uPAR), urokinase-type plasminogen activator (uPA) catalyzes the conversion of plasminogen to plasmin and the activation of matrix metalloproteases. Apart from this, uPA-uPAR interaction can lead to the activation of transcription factors, mitogenactivated protein kinase signaling pathways and RTK cascades. Elevated expression of uPA and uPAR is markedly associated with cancer progression and metastasis and correlates with a poor prognosis in clinics. Targeting the urokinase system has proved to be effective in experimental models in vitro and in vivo, however, in clinics the inhibition of the uPA/uPAR system has fallen short of expectations, suggesting that the question of the functional relevance of uPA/uPAR system is far from being moot. Recently, using CRISPR/Cas9 technology, we have shown that uPAR knockout decreases the proliferation of neuroblastoma Neuro2a cells in vitro. In the present study we demonstrate that uPAR expression is essential for maintaining the epithelial phenotype in Neuro2a cells and that uPAR silencing promotes epithelial-mesenchymal transition (EMT) and increased cell migration. Accordingly, uPAR knockout results in the downregulation of epithelial markers (E-cadherin, occludin, and claudin-5) and in the increase of mesenchymal markers (N-cadherin, α-smooth muscle actin, and interleukin-6). In search of the molecular mechanism underlying these changes, we identified uPA as a key component. Two key insights emerged as a result of this work: in the absence of uPAR, uPA is translocated into the nucleus where it is presumably involved in the activation of transcription factors (nuclear factor κB and Snail) resulting in EMT. In uPAR-expressing cells, uPAR functions as a uPA ---

The Urokinase Receptor: A Multifunctional Receptor in Cancer Cell Biology. Therapeutic Implications

“…Altogether, most reports show an active role for uPAR in EMT, even though a recent report shows that, instead, uPAR expression is essential for maintaining the epithelial phenotype in neuroblastoma Neuro2a cells, since uPAR silencing induces the down-regulation of epithelial markers (E-cadherin, occludin, and claudin-5) and the increase of mesenchymal markers (N-cadherin, α-smooth muscle actin, and interleukin-6) [ 70 ].…”

uPAR: An Essential Factor for Tumor Development

“…Since uPAR lacks transmembrane or intracellular domains, it needs to interact with transmembrane receptors and complexes to trigger downstream signaling and promote tumor cell proliferation 4 . Recently, Wang K et al 59 and Semina EV et al 64 knocked out uPAR with the CRISPR/Cas9 system, successfully resulting in suppression of human cancer cell proliferation. Silencing uPAR can inhibit the expression of the MMP2, MMP9 and P-ERK proteins in oral and tongue squamous cell carcinoma and attenuate cell proliferation 65 .…”

Proteolytic enzyme and adiponectin receptors as potential targets for COVID-19 therapy

“…Накопленные данные о роли uPA и uPAR в сосудах говорят о том, что функции урокиназной системы выходят за пределы фибринолиза, и в тканях активная урокиназа и ее рецептор оказывают ряд эффектов, направленных на их регенерацию и восстановление, однако длительное присутствие uPA в системе или чрезмерная активация uPAR могут иметь ряд противоположных эффектов. Опубликованные данные [20] свидетельствуют в пользу предположения о том, что uPAR является ловушкой урокиназы на мембране, препятствуя ее транслокации в ядро и активации транскрипционного фактора NF-kB, регулирующего эпителиально-мезенхимальный переход, как одного из маркеров фиброза. Кроме того, uPAR может регулировать продукцию клетками IL-6, а переходя в растворимую форму за счет частичного протеолиза, uPAR может функционировать как хемоаттрактант для клеток иммунной системы, связываясь с хемокиновым рецептором пептида fMLP (N-формилметионил-лейцил-фенилаланина) [21].…”