Bhattacharyya Sumit, Feferman Leo, Tobacman Joanne K
Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, 60612, United States of America.
Jesse Brown VA Medical Center, Chicago, Illinois, 60612, United States of America.
PLoS One. 2016 Apr 14;11(4):e0153463. doi: 10.1371/journal.pone.0153463. eCollection 2016.
Arylsulfatase B (B-acetylgalactosamine 4-sulfatase; ARSB) is the enzyme that removes 4-sulfate groups from the non-reducing end of the glycosaminoglycans chondroitin 4-sulfate and dermatan sulfate. Decline in ARSB has been shown in malignant prostate, colonic, and mammary cells and tissues, and decline in ARSB leads to transcriptional events mediated by galectin-3 with AP-1 and Sp1. Increased mRNA expression of GPNMB (transmembrane glycoprotein NMB) in HepG2 cells and in hepatic tissue from ARSB-deficient mice followed decline in expression of ARSB and was mediated by the microphthalmia-associated transcription factor (MITF), but was unaffected by silencing galectin-3. Since GPNMB is increased in multiple malignancies, studies were performed to determine how decline in ARSB increased GPNMB expression. The mechanism by which decline in ARSB increased nuclear phospho-MITF was due to reduced activity of SHP2, a protein tyrosine phosphatase with Src homology (SH2) domains that regulates multiple cellular processes. SHP2 activity declined due to increased binding with chondroitin 4-sulfate when ARSB was reduced. When SHP2 activity was inhibited, phosphorylations of p38 mitogen-associated phosphokinase (MAPK) and of MITF increased, leading to GPNMB promoter activation. A dominant negative SHP2 construct, the SHP2 inhibitor PHSP1, and silencing of ARSB increased phospho-p38, nuclear MITF, and GPNMB. In contrast, constitutively active SHP2 and overexpression of ARSB inhibited GPNMB expression. The interaction between chondroitin 4-sulfate and SHP2 is a novel intersection between sulfation and phosphorylation, by which decline in ARSB and increased chondroitin 4-sulfation can inhibit SHP2, thereby regulating downstream tyrosine phosphorylations by sustained phosphorylations with associated activation of signaling and transcriptional events.
芳基硫酸酯酶B（β-乙酰半乳糖胺4-硫酸酯酶；ARSB）是一种从糖胺聚糖硫酸软骨素4-硫酸酯和硫酸皮肤素的非还原端去除4-硫酸基团的酶。在恶性前列腺、结肠和乳腺细胞及组织中已显示ARSB水平下降，而ARSB水平下降会导致由半乳糖凝集素-3与AP-1和Sp1介导的转录事件。ARSB缺陷小鼠的HepG2细胞和肝组织中GPNMB（跨膜糖蛋白NMB）的mRNA表达增加，这是在ARSB表达下降之后发生的，并且由小眼相关转录因子（MITF）介导，但不受半乳糖凝集素-3沉默的影响。由于GPNMB在多种恶性肿瘤中表达增加，因此开展了研究以确定ARSB水平下降如何增加GPNMB的表达。ARSB水平下降导致核磷酸化MITF增加的机制是由于SHP2活性降低，SHP2是一种具有Src同源（SH2）结构域的蛋白酪氨酸磷酸酶，可调节多种细胞过程。当ARSB减少时，由于与硫酸软骨素4-硫酸酯的结合增加，SHP2活性下降。当SHP2活性受到抑制时，p38丝裂原相关磷酸激酶（MAPK）和MITF的磷酸化增加，导致GPNMB启动子激活。显性负性SHP2构建体、SHP2抑制剂PHSP1以及ARSB沉默均增加了磷酸化p38、核MITF和GPNMB。相反，组成型活性SHP2和ARSB的过表达抑制了GPNMB的表达。硫酸软骨素4-硫酸酯与SHP2之间的相互作用是硫酸化和磷酸化之间的一个新交叉点，通过这个交叉点，ARSB水平下降和硫酸软骨素4-硫酸化增加可抑制SHP2，从而通过信号传导和转录事件的相关激活导致的持续磷酸化来调节下游酪氨酸磷酸化。
