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Yoo, Lang,Chung, Kwang Chul American Society for Biochemistry and Molecular Bi 2018 The Journal of biological chemistry Vol.293 No.4
<P>Mutations in the gene for the serine/threonine protein kinase PTEN-induced putative kinase 1 (PINK1) are the second most frequent cause of autosomal recessive Parkinson's disease (PD). Via its kinase activity, PINK1 regulates neuronal cell survival and mitochondrial quality control. Numerous reports have revealed that PINK1 has diverse and physiologically significant functions, and therefore its activity should be tightly regulated. However, the molecular mechanisms regulating PINK1 stability and the modulator(s) involved have not been elucidated. In this study, we demonstrate that the ubiquitin E3 ligase carboxyl terminus of Hsp70-interacting protein (CHIP) promotes PINK1 ubiquitination and decreases its steady-state levels. Moreover, PINK1 levels were strongly reduced in HEK293 and SH-SY5Y cells exposed to the apoptosis-inducer staurosporine. Of note, we found that this reduction resulted from CHIP-mediated PINK1 ubiquitination. Accordingly, siRNA-mediated CHIP knockdown reduced susceptibility to staurosporine-induced cell death. Taken together, these findings suggest that CHIP plays a role in negative regulation of PINK1 stability and may suppress PINK1's cytoprotective effect during staurosporine-induced mammalian cell death. We propose that this PINK1 regulatory pathway might contribute to Parkinson's disease pathogenesis.</P>
Park, Eui-Soon,Choi, Seunga,Shin, Bongjin,Yu, Jungeun,Yu, Jiyeon,Hwang, Jung-Me,Yun, Hyeongseok,Chung, Young-Ho,Choi, Jong-Soon,Choi, Yongwon,Rho, Jaerang American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.15
<P>The signaling pathway downstream of TNF receptor (TNFR) is involved in the induction of a wide range of cellular processes, including cell proliferation, activation, differentiation, and apoptosis. TNFR-associated factor 2 (TRAF2) is a key adaptor molecule in TNFR signaling complexes that promotes downstream signaling cascades, such as nuclear factor-kappa B (NF-kappa B) and mitogen-activated protein kinase activation. TRAF-interacting protein (TRIP) is a known cellular binding partner of TRAF2 and inhibits TNF-induced NF-kappa B activation. Recent findings that TRIP plays a multifunctional role in antiviral response, cell proliferation, apoptosis, and embryonic development have increased our interest in exploring how TRIP can affect the TNFR-signaling pathway on a molecular level. In our current study, we demonstrated that TRIP is negatively involved in the TNF-induced inflammatory response through the down-regulation of proinflammatory cytokine production. Here, we demonstrated that the TRAF2-TRIP interaction inhibits Lys(63)-linked TRAF2 ubiquitination by inhibiting TRAF2 E3 ubiquitin (Ub) ligase activity. The TRAF2-TRIP interaction inhibited the binding of sphingosine 1-phosphate, which is a cofactor of TRAF2 E3 Ub ligase, to the TRAF2 RING domain. Finally, we demonstrated that TRIP functions as a negative regulator of proinflammatory cytokine production by inhibiting TNF-induced NF-kappa B activation. These results indicate that TRIP is an important cellular regulator of the TNF-induced inflammatory response.</P>
Disrupted-in-schizophrenia 1 (DISC1) Regulates Dysbindin Function by Enhancing Its Stability
Lee, Seol-Ae,Kim, Seong-Mo,Suh, Bo Kyoung,Sun, Hwa-Young,Park, Young-Un,Hong, Ji-Ho,Park, Cana,Nguyen, Minh Dang,Nagata, Koh-ichi,Yoo, Joo-Yeon,Park, Sang Ki American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.11
<P>Dysbindin and DISC1 are schizophrenia susceptibility factors playing roles in neuronal development. Here we show that the physical interaction between dysbindin and DISC1 is critical for the stability of dysbindin and for the process of neurite outgrowth. We found that DISC1 forms a complex with dysbindin and increases its stability in association with a reduction in ubiquitylation. Furthermore, knockdown of DISC1 or expression of a deletion mutant, DISC1 lacking amino acid residues 403–504 of DISC1 (DISC1<SUP>Δ403–504</SUP>), effectively decreased levels of endogenous dysbindin. Finally, the neurite outgrowth defect induced by knockdown of DISC1 was partially reversed by coexpression of dysbindin. Taken together, these results indicate that dysbindin and DISC1 form a physiologically functional complex that is essential for normal neurite outgrowth.</P>
Choi, Yun-Seok,Lee, Yun-Ju,Lee, Seo-Yeon,Shi, Lei,Ha, Jung-Hye,Cheong, Hae-Kap,Cheong, Chaejoon,Cohen, Robert E.,Ryu, Kyoung-Seok American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.4
<P>The ubiquitin E2 enzymes, Ube2g1 and Ube2r1, are able to synthesize Lys-48-linked polyubiquitins without an E3 ligase but how that is accomplished has been unclear. Although both E2s contain essential acidic loops, only Ube2r1 requires an additional C-terminal extension (184–196) for efficient Lys-48-ubiquitylation activity. The presence of Tyr-102 and Tyr-104 in the Ube2g1 acidic loop enhanced both ubiquitin binding and Lys-48-ubiquitylation and distinguished Ube2g1 from the otherwise similar truncated Ube2r1<SUP>1–183</SUP> (Ube2r1C). Replacement of Gln-105–Ser-106–Gly-107 in the acidic loop of Ube2r1C (Ube2r1C<SUP>YGY</SUP>) by the corresponding residues from Ube2g1 (Tyr-102–Gly-103–Tyr-104) increased Lys-48-ubiquitylation activity and ubiquitin binding. Two E2∼UB thioester mimics (oxyester and disulfide) were prepared to characterize the ubiquitin binding activity of the acidic loop. The oxyester but not the disulfide derivative was found to be a functional equivalent of the E2∼UB thioester. The ubiquitin moiety of the Ube2r1C<SUP>C93S</SUP>-[<SUP>15</SUP>N]UB<SUP>K48R</SUP> oxyester displayed two-state conformational exchange, whereas the Ube2r1C<SUP>C93S/YGY</SUP>-[<SUP>15</SUP>N]UB<SUP>K48R</SUP> oxyester showed predominantly one state. Together with NMR studies that compared UB<SUP>K48R</SUP> oxyesters of the wild-type and the acidic loop mutant (Y102G/Y104G) forms of Ube2g1, <I>in vitro</I> ubiquitylation assays with various mutation forms of the E2s revealed how the intramolecular interaction between the acidic loop and the attached donor ubiquitin regulates Lys-48-ubiquitylation activity.</P>
Jung, Soo-A,Park, Yong-Man,Hong, Seung-Woo,Moon, Jai-Hee,Shin, Jae-Sik,Lee, Ha-Reum,Ha, Seung-Hee,Lee, Dae-Hee,Kim, Jeong Hee,Kim, Seung-Mi,Kim, Jeong Eun,Kim, Kyu-pyo,Hong, Yong Sang,Choi, Eun Kyung American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.16
<P>YM155, which blocks the expression of survivin, a member of the inhibitor of apoptosis (IAP) family, induces cell death in a variety of cancer types, including prostate, bladder, breast, leukemia, and non-small lung cancer. However, the mechanism underlying gastric cancer susceptibility and resistance to YM155 is yet to be specified. Here, we demonstrate that cIAP1 stability dictates resistance to YM155 in human gastric cancer cells. Treatment of human gastric cancer cells with YM155 differentially induced cell death dependent on the stability of cIAP1 as well as survivin. Transfection with cIAP1 expression plasmids decreased cell sensitivity to YM155, whereas knockdown of endogenous cIAP1 using RNA interference enhanced sensitivity to YM155. In addition, double knockdown of survivin and cIAP1 significantly induced cell death in the YM155-resistant cell line, MKN45. We also showed that YM155 induced autoubiquitination and proteasome-dependent degradation of cIAP1. Surprisingly, survivin affected the stability of cIAP1 through binding, contributing to cell sensitivity to YM155. Thus, our findings reveal that YM155 sensitizes human gastric cancer cells to apoptotic cell death by degrading cIAP1, and furthermore, cIAP1 in gastric cancer cells may act as a PD marker for YM155 treatment.</P>
Lee, Nam Soo,Chang, Hae Ryung,Kim, Soomi,Ji, Jae-Hoon,Lee, Joorak,Lee, Hyun Ji,Seo, Yoojeong,Kang, Misun,Han, Joo Seok,Myung, Kyungjae,Kim, Yonghwan,Kim, Hongtae American Society for Biochemistry and Molecular Bi 2018 The Journal of biological chemistry Vol.293 No.2
<P>Cells have evolved sophisticated mechanisms to maintain genomic integrity in response to DNA damage. Ionizing radiation (IR)–induced DNA damage results in the formation of IR-induced foci (iRIF) in the nucleus. The iRIF formation is part of the DNA damage response (DDR), which is an essential signaling cascade that must be strictly regulated because either the loss of or an augmented DDR leads to loss of genome integrity. Accordingly, negative regulation of the DDR is as critical as its activation. In this study, we have identified ring finger protein 126 (RNF126) as a negative regulator of the DDR from a screen of iRIF containing 53BP1. RNF126 overexpression abolishes not only the formation of 53BP1 iRIF but also of RNF168, FK2, RAP80, and BRCA1. However, the iRIF formation of γH2AX, MDC1, and RNF8 is maintained, indicating that RNF126 acts between RNF8 and RNF168 during the DDR. In addition, RNF126 overexpression consistently results in the loss of RNF168-mediated H2A monoubiquitination at lysine 13/15 and inhibition of the non-homologous end joining capability. Taken together, our findings reveal that RNF126 is a novel factor involved in the negative regulation of DDR, which is important for sustaining genomic integrity.</P>
Kim, Dae Hong,Hwang, Jae Sam,Lee, Ik Hwan,Nam, Seung Taek,Hong, Ji,Zhang, Peng,Lu, Li Fang,Lee, Junguee,Seok, Heon,Pothoulakis, Charalabos,Lamont, John Thomas,Kim, Ho American Society for Biochemistry and Molecular Bi 2016 The Journal of biological chemistry Vol.291 No.7
<P>The epithelial cells of the gut form a physical barrier against the luminal contents. The collapse of this barrier causes inflammation, and its therapeutic restoration can protect the gut against inflammation. EGF enhances mucosal barrier function and increases colonocyte proliferation, thereby ameliorating inflammatory responses in the gut. Based on our previous finding that the insect peptide CopA3 promotes neuronal growth, we herein tested whether CopA3 could increase the cell proliferation of colonocytes, enhance mucosal barrier function, and ameliorate gut inflammation. Our results revealed that CopA3 significantly increased epithelial cell proliferation in mouse colonic crypts and also enhanced colonic epithelial barrier function. Moreover, CopA3 treatment ameliorated Clostridium difficile toxin As-induced inflammation responses in the mouse small intestine (acute enteritis) and completely blocked inflammatory responses and subsequent lethality in the dextran sulfate sodium-induced mouse model of chronic colitis. The marked CopA3-induced increase of colonocyte proliferation was found to require rapid protein degradation of p21(Cip1/Waf1), and an in vitro ubiquitination assay revealed that CopA3 directly facilitated ubiquitin ligase activity against p21(Cip1/Waf1). Taken together, our findings indicate that the insect peptide CopA3 prevents gut inflammation by increasing epithelial cell proliferation and mucosal barrier function.</P>