MYL9：肌球蛋白“細(xì)胞動力馬達(dá)”家族一員，癌細(xì)胞遷移動力靶點(diǎn)？
日期：2023-07-12 17:15:38
MYL9作為肌球蛋白的調(diào)節(jié)性輕鏈（myosin light chain，MLC），是激活肌球蛋白運(yùn)動活性的關(guān)鍵環(huán)節(jié)，為細(xì)胞運(yùn)動提供動力。然而，細(xì)胞遷移是造成惡性腫瘤轉(zhuǎn)移的關(guān)鍵。多項(xiàng)研究表明，MYL9為癌細(xì)胞遷移提供動力，參與腫瘤的發(fā)生、發(fā)展。CD69被認(rèn)為是淋巴細(xì)胞的早期激活標(biāo)志物，最新研究闡明了一種新機(jī)制，MYL9可以作為CD69的配體，參與T細(xì)胞募集到炎癥性肺部 [1]。
此外，MYL9-CD69系統(tǒng)可誘導(dǎo)腫瘤微環(huán)境中的效應(yīng)T細(xì)胞衰竭，并削弱抗腫瘤免疫反應(yīng)。通過阻斷MYL9和CD69之間的相互作用，有利于保持較高的抗腫瘤免疫反應(yīng) [2]。因此，MYL9作為肌球蛋白“細(xì)胞動力馬達(dá)”家族一員，可能是癌癥免疫治療的下一個(gè)新藥物靶點(diǎn)！
1. 什么是肌球蛋白？
肌球蛋白是一類高度保守的蛋白，是細(xì)胞骨架的重要組成部分，也是基于肌動蛋白依賴性的分子馬達(dá)。肌球蛋白約占人體總蛋白的15%~25%，主要存在平滑肌中，其家族比較大，目前已發(fā)現(xiàn)人40個(gè)肌球蛋白基因，分別代表12類的超大家族（I-XII）。肌球蛋白的分子結(jié)構(gòu)包括重鏈（myosin heavy chain，MHC）和輕鏈（myosin light chain，MLC），輕鏈又分為基礎(chǔ)性MLC（MLC I）和調(diào)節(jié)性MLC（MLC II）。肌球蛋白是一種多功能蛋白質(zhì)，在細(xì)胞的變形、黏附、運(yùn)動及細(xì)胞的遷移方面有巨大的作用，被稱為“細(xì)胞動力的馬達(dá)”（圖1） [3-6]。
圖1. 肌球蛋白超家族 [3]
2. 什么是MYL9？
肌球蛋白監(jiān)管輕鏈MYL9（myosin regulatory light chain 9，又稱MLC2, MRLC1或MLC-2C）是組成肌球蛋白的調(diào)節(jié)性輕鏈。人MYL9基因位于染色體20q11.23上，包含8621個(gè)堿基，8個(gè)內(nèi)含子和17個(gè)外顯子。它編碼的20KD肌球蛋白監(jiān)管輕鏈，是肌球蛋白的重要組成部分。肌球蛋白按區(qū)域分為頭部、頸部和尾部。頭部是球形，含有ATP結(jié)合和肌動蛋白結(jié)合部位，用于催化ATP的水解釋放化學(xué)能量，并與肌動蛋白結(jié)合。頸部有兩條調(diào)節(jié)性輕鏈纏繞成α螺旋狀，可結(jié)合肌球蛋白輕鏈和鈣調(diào)素。尾部是卷曲的螺旋結(jié)構(gòu)，含有羥基 （圖2）[7]。
MYL9在正常組織及腫瘤組織中均廣泛表達(dá)，如肌肉組織、內(nèi)臟組織、肺癌、前列腺癌等。迄今為止，已有大量研究表明，MYL9作為肌球蛋白的關(guān)鍵成員，通過多種調(diào)節(jié)因子參與生物體內(nèi)諸多的功能，如肌肉運(yùn)動，細(xì)胞遷移，細(xì)胞內(nèi)吞，有絲分裂和信號轉(zhuǎn)導(dǎo)等，尤其在腫瘤細(xì)胞的遷移和增殖中發(fā)揮著重要的作用 [8-11]。
圖2. MYL9是肌球蛋白“細(xì)胞動力馬達(dá)”關(guān)鍵成員 [7]
3. MYL9相關(guān)的信號通路
MYL9主要通過兩大系統(tǒng)起到調(diào)控的作用：1）Rho肌酶（rho-kinase, ROCK）系統(tǒng)；2）肌球蛋白輕鏈肌酶（myosin light chain kinase, MLCK）系統(tǒng)。除了這兩個(gè)系統(tǒng)之外，還涉及鈣調(diào)蛋白依賴的蛋白激酶II、ILK、PKA、ZIPK、PKC以及肌球蛋白輕鏈磷酸酶MLCP抑制分子CP17等相關(guān)重要分子 [12-14]。
如圖3所示，MLCK和ROCK系統(tǒng)激活，并與鈣離子Ca2+結(jié)合，增加細(xì)胞內(nèi)鈣離子Ca2+濃度，又可以激活肌球蛋白輕鏈肌酶活性和MYL9的磷酸化。具體而言，ROCK是肌球蛋白輕鏈的最直接底物之一，其介導(dǎo)MYL9基因的磷酸化及去磷酸化作用。此外，ROCK可促進(jìn)細(xì)胞內(nèi)Ca2+濃度的增加，通過激活Ca2+／鈣調(diào)蛋白依賴的MLCK，在MLCK的作用下引起MYL9的磷酸化 [12]。
MYL9的磷酸化增強(qiáng)肌球蛋白和肌動蛋白之間的相互作用，以及肌球蛋白輕鏈頭部ATP酶的活性，從而促進(jìn)細(xì)胞骨架的重構(gòu)，并增加細(xì)胞的增殖、分化、粘附和遷移的能力。RhoA抑制因子能有效的直接抑制其下游的效應(yīng)蛋白Rock，從而對MYL9的表達(dá)和磷酸化作用起抑制作用，進(jìn)而抑制腫瘤細(xì)胞肌動蛋白形成等生物學(xué)行為，同時(shí)對腫瘤的侵襲、轉(zhuǎn)移和生長也起抑制作用 [12]。
圖3. MYL9主要通過MLCK和ROCK兩大系統(tǒng)起到調(diào)控的作用 [12]
4. MYL9在腫瘤等疾病中的作用
許多研究表明，MYL9通過磷酸化和去磷酸化調(diào)節(jié)ATP酶活性以及肌球蛋白的收縮，從而控制細(xì)胞的運(yùn)動、黏附和變形等功能。惡性腫瘤的特點(diǎn)之一是浸潤性生長和遠(yuǎn)處轉(zhuǎn)移，這表明與細(xì)胞運(yùn)動相關(guān)的分子MYL9異常表達(dá)可能影響腫瘤的發(fā)展。許多研究已經(jīng)報(bào)道了MYL9參與腫瘤發(fā)病機(jī)制，不僅能抑制腫瘤，同時(shí)也能促進(jìn)腫瘤生長 [15-17]。
4.1 MYL9和腫瘤
4.1.1 MYL9促進(jìn)腫瘤
MYL9在多種腫瘤中呈現(xiàn)增加的表達(dá)和磷酸化水平。在乳腺癌和肝癌中，MYL9主要通過促進(jìn)腫瘤細(xì)胞運(yùn)動來促使腫瘤發(fā)生侵襲 [18-19]。此外，在膠質(zhì)母細(xì)胞瘤中，MYL9的表達(dá)量和磷酸化水平也有所增加。高水平的MYL9表達(dá)與膠質(zhì)母細(xì)胞瘤患者預(yù)后較差以及復(fù)發(fā)性膠質(zhì)母細(xì)胞瘤患者中MYL9表達(dá)增加相關(guān)聯(lián) [8]。另外，胰腺導(dǎo)管腺癌和卵巢上皮性腫瘤中也觀察到MYL9的增加表達(dá)。臨床數(shù)據(jù)分析提示MYL9可作為胰腺導(dǎo)管腺癌和卵巢上皮性腫瘤的獨(dú)立預(yù)后因素 [14, 20]。
同樣地，食管鱗狀細(xì)胞癌細(xì)胞系中MYL9呈顯著上調(diào)，并且與腫瘤細(xì)胞中MYL9表達(dá)高的患者總生存期和無復(fù)發(fā)生存期較差相關(guān) [21]。此外，高表達(dá)MYL9促進(jìn)骨肉瘤的進(jìn)展 [22]。綜上所述，這些研究結(jié)果表明MYL9可能通過促進(jìn)腫瘤細(xì)胞運(yùn)動影響腫瘤的生長和侵襲轉(zhuǎn)移，并且可能成為多種腫瘤的預(yù)后標(biāo)志物和治療靶點(diǎn)。
4.1.2 MYL9抑制腫瘤
但與之相反的是，基于微陣列和蛋白質(zhì)組學(xué)分析，發(fā)現(xiàn)MYL9蛋白在前列腺組織中表達(dá)下降，與年齡、病理分期、轉(zhuǎn)移和PSA水平等相關(guān) [23]。類似地，在膀胱癌和胃癌中也觀察到MYL9表達(dá)下調(diào) [24-25]。然而，進(jìn)一步的細(xì)胞實(shí)驗(yàn)證明，MYL9缺乏減少了胃癌細(xì)胞的增殖并增強(qiáng)了細(xì)胞凋亡 [15]。在人類結(jié)直腸癌中，MYL9的表達(dá)和磷酸化水平降低 [26]。細(xì)胞實(shí)驗(yàn)證實(shí)，通過上調(diào)MYL9，可以抑制腫瘤細(xì)胞的增殖、侵襲和遷移，并促進(jìn)結(jié)腸癌干細(xì)胞的凋亡 [27-28]。
生物信息學(xué)分析發(fā)現(xiàn)，低MYL9表達(dá)可能與非小細(xì)胞肺癌的發(fā)展和轉(zhuǎn)移有關(guān) [29-30]。在乳腺癌中，MYL9的上調(diào)顯著降低了癌細(xì)胞的運(yùn)動能力 [15]。然而，一些文獻(xiàn)提出MYL9在分子水平上的表達(dá)增加了乳腺癌細(xì)胞的遷移 [15, 31]。根據(jù)目前的文獻(xiàn)，MYL9在惡性腫瘤中的作用存在爭議。總體而言，MYH9在腫瘤中的作用復(fù)雜多樣，可能成為治療靶點(diǎn)和預(yù)后評估的重要指標(biāo)。
4.2 MYL9和其它疾病
MYL9不僅與腫瘤相關(guān)，還在心血管、炎癥和神經(jīng)系統(tǒng)等疾病中發(fā)揮作用 [32-35]。動脈粥樣硬化模型顯示，隨著斑塊增加，MYL9表達(dá)顯著下調(diào)。MYL9受到血管緊張素II（Angiotensin II/AGT）和細(xì)胞因子PDGF-BB的刺激下調(diào)。血管緊張素II和PDGF-BB是重要的細(xì)胞因子，在血管損傷過程中促進(jìn)平滑肌細(xì)胞增殖和遷移。因此，MYL9可能在動脈粥樣硬化的發(fā)展中起重要作用 [36-37]。
陸續(xù)的報(bào)道表明MYL9蛋白是CD69分子的新配基，MYL9-CD69系統(tǒng)參與調(diào)節(jié)免疫應(yīng)答 [2, 38-41]。阻斷MYL9-CD69之間的互動可改善實(shí)驗(yàn)鼠的過敏性呼吸道炎癥，如哮喘 [2]；在炎癥時(shí)，血管受損并導(dǎo)致血小板活化，進(jìn)而產(chǎn)生MYL9網(wǎng)絡(luò)結(jié)構(gòu)和各種凝血因子，接著MYL9能夠與CD69陽性的特異性T細(xì)胞結(jié)合，促使免疫細(xì)胞聚集到炎癥部位，并產(chǎn)生效應(yīng)細(xì)胞因子和趨化因子，從而有效激活免疫反應(yīng)（圖4） [41]。
圖4. MYL9-CD69系統(tǒng)參與調(diào)節(jié)免疫應(yīng)答 [42]
5. MYL9的臨床研究前景
MYL9在肺癌、乳腺癌、前列腺癌、胃癌等多種不同類型的惡性腫瘤中均有異常表達(dá)，并且往往與不良預(yù)后密切相關(guān)，其表達(dá)的臨床意義根據(jù)癌組織的不同而不同。更值得關(guān)注的是，MYL9可能作為CD69新配體，兩者的相互作用促進(jìn)CTL的滯留，使其受到腫瘤抗原的慢性刺激而導(dǎo)致T細(xì)胞衰竭。在腫瘤微環(huán)境中，抗原特異性細(xì)胞毒性T細(xì)胞（cytotoxic lymphocytes，CTL）是機(jī)體抗腫瘤免疫的重要防線。這意味著抗MYL9/CD69可能是癌癥免疫療法的理想治療靶點(diǎn)。
目前，國內(nèi)外針對MYL9抗癌的臨床實(shí)踐經(jīng)驗(yàn)尚淺，但其作為各類腫瘤治療的靶標(biāo)的可能性已得到了越來越多的證據(jù)支持。因此，MYL9作為分子標(biāo)志物和潛在的靶標(biāo)，在惡性腫瘤的早期診斷、預(yù)后預(yù)測以及靶向治療中將具有極大的臨床應(yīng)用價(jià)值。
為鼎力協(xié)助科研和藥企人員針對MYL9在腫瘤等疾病中的臨床應(yīng)用研究，CUSABIO推出MYL9活性蛋白（Code: CSB-YP015318HU）產(chǎn)品，助力您在MYL9機(jī)制方面的研究或其潛在臨床價(jià)值的探索。（點(diǎn)擊查看MYL9系列產(chǎn)品： MYL9蛋白； MYL9抗體）
Recombinant Human Myosin regulatory light polypeptide 9(MYL9) (Active) (Code: CSB-YP015318HU)
The Greater than 95% as determined by SDS-PAGE. (Tris-Glycine gel) Discontinuous SDS-PAGE (reduced) with 5% enrichment gel and 15% separation gel.
Immobilized Human MYL9 at 2μg/mL can bind Anti-MYL9 recombinant antibody (CSB-RA015318MA1HU), the EC50 is 4.628-6.430 ng/mL.
參考文獻(xiàn)：
[1] Iwamura, Chiaki, et al. "Elevated Myl9 reflects the Myl9-containing microthrombi in SARS-CoV-2-induced lung exudative vasculitis and predicts COVID-19 severity." Proceedings of the National Academy of Sciences 119.33 (2022): e2203437119.
[2] Kimura, Motoko Y., et al. "A new therapeutic target: the CD69-Myl9 system in immune responses." Seminars in immunopathology. vol. 41. Springer Berlin Heidelberg, 2019.
[3] Sellers, James R. "Myosins: a diverse superfamily." Biochimica et Biophysica Acta (BBA)-Molecular Cell Research 1496.1 (2000): 3-22.
[4] Fitz, Gillian N., et al. "Protrusion growth driven by myosin-generated force." Developmental Cell 58.1 (2023): 18-33.
[5] Hartman, M. Amanda, and James A. Spudich. "The myosin superfamily at a glance. "Journal of cell science 125.7 (2012): 1627-1632.
[6] Lewis, Christopher TA, and Julien Ochala. "Myosin heavy chain as a novel key modulator of striated muscle resting state. "Physiology 38.1 (2023): 3-9.
[7] Bhanu P. Jena. "Myosin: Cellular Molecular Motor" Cellular Nanomachines (2020): 79-89.
[8] Kruthika, Banavathy S., et al. "Expression pattern and prognostic significance of myosin light chain 9 (MYL9): a novel biomarker in glioblastoma." Journal of Clinical Pathology 72.10 (2019): 677-681.
[9] Shehadeh, Lina A., et al. "Dynamic regulation of vascular myosin light chain (MYL9) with injury and aging." PLoS One 6.10 (2011): e25855.
[10] Zhu, Kongxi, et al. "Long non-coding RNA MBNL1-AS1 regulates proliferation, migration, and invasion of cancer stem cells in colon cancer by interacting with MYL9 via sponging microRNA-412-3p." Clinics and research in hepatology and gastroenterology 44.1 (2020): 101-114.
[11] Jalagadugula, Gauthami, et al. "Regulation of platelet myosin light chain (MYL9) by RUNX1: implications for thrombocytopenia and platelet dysfunction in RUNX1 haplodeficiency." Blood, The Journal of the American Society of Hematology 116.26 (2010): 6037-6045.
[12] Moreno, Carolina Araujo, et al. "Homozygous deletion in MYL9 expands the molecular basis of megacystis-microcolon- intestinal hypoperistalsis syndrome." European Journal of Human Genetics 26.5 (2018): 669-675.
[13] Licht, Alexander H., et al. "Junb regulates arterial contraction capacity, cellular contractility, and motility via its target Myl9 in mice." The Journal of clinical investigation 120.7 (2010): 2307-2318.
[14] Matsushita, Katsunori, et al. "Clinicopathological significance of MYL9 expression in pancreatic ductal adenocarcinoma." Cancer Reports 5.10 (2022 ): e1582.
[15] Lv, Minghe, Lumeng Luo, and Xue Chen. "The landscape of prognostic and immunological role of myosin light chain 9 (MYL9) in human tumors." Immunity. Inflammation and Disease 10.2 (2022): 241-254.
[16] Gilles, Laure, et al. "MAL/SRF complex is involved in platelet formation and megakaryocyte migration by regulating MYL9 (MLC2) and MMP9." Blood, The Journal of the American Society of Hematology 114.19 (2009): 4221-4232.
[17] Tan, Xiang, and Mingwu Chen. "MYLK and MYL9 expression in non-small cell lung cancer identified by bioinformatics analysis of public expression data." Tumor Biology 35 (2014): 12189-12200.
[18] Luo, Xue-Gang, et al. "Histone methyltransferase SMYD3 promotes MRTF-A-mediated transactivation of MYL9 and migration of MCF-7 breast cancer cells." Cancer letters 344.1 (2014): 129-137.
[19] Hirasawa, Yuichi, et al. "Methylation status of genes upregulated by demethylating agent 5-aza-2′-deoxycytidine in hepatocellular carcinoma." Oncology 71.1-2 (2007): 77-85.
[20] Deng, Yuao, et al. "High expression of MYL9 indicates poor clinical prognosis of epithelial ovarian cancer." Recent Patents on Anti-Cancer Drug Discovery 16.4 (2021): 533-539.
[21] Wang, Jian-Hua, et al. "Expression and prognostic significance of MYL9 in esophageal squamous cell carcinoma." ploS one 12.4 (2017): e0175280.
[22] Zhao, S., W. Xiong, and K. Xu. "MiR-663a, regulated by lncRNA GAS5, contributes to osteosarcoma development through targeting MYL9. "Human & Experimental Toxicology 39.12 (2020): 1607-1618.
[23] Huang, Ya-qiang, et al. "Decreased expression of myosin light chain MYL9 in stroma predicts malignant progression and poor biochemical recurrence- free survival in prostate cancer." medical oncology 31 (2014): 1-9.
[24] Huang, Chu-Han, et al. "MYL9 deficiency is neonatal lethal in mice due to abnormalities in the lung and the muscularis propria of the bladder and intestine ." Plos one 17.7 (2022): e0270820.
[25] Dong, Ningxin, et al. "Identification and validation of critical genes with prognostic value in gastric cancer." Frontiers in Cell and Developmental Biology 10 (2022): 1072062.
[26] Qiu, Xiao, et al. "Weighted gene co-expression network analysis identified MYL9 and CNN1 are associated with recurrence in colorectal cancer." journal of Cancer 11.8 (2020): 2348.
[27] Zhou, Rui, et al. "PRPF19 facilitates colorectal cancer liver metastasis through activation of the Src-YAP1 pathway via K63-linked ubiquitination of MYL9." Cell Death & Disease 14.4 (2023): 258.
[28] Feng, Min, et al. "Myosin light chain 9 promotes the proliferation, invasion, migration and angiogenesis of colorectal cancer cells by binding to Yes- associated protein 1 and regulating Hippo signaling." Bioengineered 13.1 (2022): 96-106.
[29] Sheng, Meiling, Zhaohui Dong, and Yanping Xie. "Identification of tumor-educated platelet biomarkers of non-small-cell lung cancer. "OncoTargets and therapy (2018): 8143-8151.
[30] Tan, Xiang, and Mingwu Chen. "MYLK and MYL9 expression in non-small cell lung cancer identified by bioinformatics analysis of public expression data." Tumor Biology 35 (2014): 12189-12200.
[31] Zhang, Chunling, et al. "Myocardin-related transcription factor A is up-regulated by 17β-estradiol and promotes migration of MCF-7 breast cancer cells via transactivation of MYL9 and CYR61." Acta Biochim Biophys Sin 45.11 (2013): 921-927.
[32] Kandler, Justin L., et al. "Compound heterozygous loss of function variants in MYL9 in a child with megacystis-microcolon intestinal hypoperistalsis syndrome." Molecular Genetics & Genomic Medicine 8.11 (2020): e1516.
[33] Kobayashi, Hironobu, et al. "Increased Myosin light chain 9 expression during Kawasaki disease vasculitis." Frontiers in Immunology 13 (2023). 1036672.
[34] Xiong, Yao, et al. "Targeting MRTF/SRF in CAP2-dependent dilated cardiomyopathy delays disease onset." jci insight 4.6 (2019).
[35] Sun, L., et al. "Decreased platelet expression of myosin regulatory light chain polypeptide (MYL9) and other genes with platelet dysfunction and CBFA2/ RUNX1 mutation: insights from platelet expression profiling." Journal of Thrombosis and Haemostasis 5.1 (2007): 146-154.
[36] Wen, Dingke, et al. "Single-cell RNA sequencing reveals the pathogenic relevance of intracranial atherosclerosis in blood blister-like aneurysms." Frontiers in Immunology 13 (2022): 927125.
[37] Hwang, Ki-Chul. "The Role of MicroRNAs in Vascular Diseases; Smooth Muscle Cell Differentiation and De-Differentiation. "Korean Circulation Journal 44.4 (2014): 218-219.
[38] Hayashizaki, Koji, et al. "Myosin light chains 9 and 12 are functional ligands for CD69 that regulate airway inflammation." science immunology 1.3 (2016 ): eaaf9154-eaaf9154.
[39] Nakayama, Toshinori, et al. "CD4+ T cells in inflammatory diseases: pathogenic T-helper cells and the CD69-Myl9 system." International Immunology 33.12 (2021): 699-704.
[40] Yokoyama, Masaya, et al. "Myosin light chain 9/12 regulates the pathogenesis of inflammatory bowel disease." Frontiers in Immunology 11 (2021): 594297.
[41] Onodera, Atsushi, Kota Kokubo, and Toshinori Nakayama. "Epigenetic and transcriptional regulation in the induction, maintenance, heterogeneity and recall-response of effector and memory Th2 cells." Frontiers in Immunology 9 (2018): 2929.
